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MFJ-784B Manual Rev. 1C

1. Operation MFJ 784B Instruction Manual 3 Contents of This Chapter gt Initial Operation CW Operation Page 3 2 Page 3 3 SSB and other voice modes Operation Page 34 gt Front Panel Description PWR LED Input Level LED AGC Button Program Button Memory Button Filters Switch Tunable Filters Controls Manual Notch Button Auto Notch Button Noise Reduction Control Noise Reduction Button Volume Control Speaker Button DSP Button Power Button Page 36 Page 36 Page 36 Page 3 7 Page 3 7 Page 3 8 Page 3 8 Page 3 9 Page 3 10 Page 3 11 Page 3 12 Page 3 12 Page 3 12 Page 3 12 Page 3 13 Page 3 13 Operation Error Main Document Only 1 MF 784B Instruction Manual Initial Operation Connect the MF 784B as outlined in Chapter 2 To prepare the unit set the controls as follows Control Position Meaning AGC button out AGC off Program button N A N A Memory button out normal Tunable Pre Set mode Filters switch CW CW filter Tunable Filters left knob center middle center freq Manual Notch button out manual notch off Tunable Filters right knob full counter clockwise maximum bandwidth Auto Notch button out auto notch off Noise Reduction control full counter clockwise minimum reduction Noise Reduction button out noise reduction off Volume control full counter clockwise minimum volume Speaker button in speaker on DSP button out DSP bypassed Power button out MEF 784B off
2. Warning Damage or improper operation may occur if the polarity current or voltage of the supply is incorrect See the installation section on page 2 2 Please don t assume your power supply wiring is correct The external power supply should be connected and on The headphones and or speaker should be connected to the correct jacks Turn the power on by pressing the DSP s Power button The PWR LED will glow red The red glow indicates the normal filter mode is selected and the microprocessor is operating This LED will glow green if the memory filters are selected Press and release the Memory button if this LED is green Operation Error Main Document Only 2 MFJ 784B Instruction M anual CW Operation This example will demonstrate how the CW filter operates and show you how to adjust the audio level from the station s receiver for proper DSP operation If your receiver doesn t operate CW you can skip to the SSB section That section works for AM FM and SSB Before attempting to operate your MFJ 784B you must familiarize yourself with the DSP controls be sure you have read the preceding sections Your MFJ 784B should be set up as outlined in the initial operation section on the preceding page Tune in a CW station and adjust your receiver for normal comfortable levels of pitch and volume Next push and lock the DSP button in Adjust the DSP s Volume control to a comfortable setting Make sure the left Tunab
3. MFJ 784B Instruction M anual Contents Fas ES ba ge ccc cpm 1 Before Reading This Manual ees iv Chapter 1 Introduction metae Rien 1 1 Introduction to DSP zaiana aa a Se a aa aa ae a a aai 1 2 Product Overview Block Diagram 2 ee en Front Panel Layout siisii 15 Back Panel Layout Filter Specifications EEN Unit Specifications tr kk ELLLER ELLLER ERE General Specifications Input Output Specifications sese 18 Chapter 2 Installation see Back Panel Connections Basic Connections nee nen Setting Receive Audio Level Input Level Increasing Headphone Audio Lewvel ss 24 Passing Sidetone TR Connection iin 25 CW Sidetone Filter WE 2 6 DSP to TNC Conmmechore ENEE 2 6 Chapter 3 Operation 3 1 ise e Clg eee esesseee teen tnnt ttem tente tente ttentenas 32 CW Operation su get te iem pepe uda 33 SSB and other voice modes Operation 34 Front Panel Description Program Button IW ue wn el Filters Switch Tunable Filters Controls Manual Notch Button een MF 784B Instruction Manual Auto Notch Button Noise Reduction Control Noise Reduction Button Chapter 4 Advanced Features 222222 4 1 Chapter 5 Filter Description Memory Filters 2 epo ee i tet tb Eo oce ana Saving Memory Filters e Ee o ndia e Mein E Talk Operati
4. Turnthe Filters switch to the position where the new filter is to be saved 4 Press and hold the Program button The LEDs will light red and the DSP will beep in one second Release the Program button This memory position will now operate with these settings whenever memory mode is selected M emory button in Advanced Features Error Main Document Only 3 MF 784B Instruction Manual CW Spotting Tone To help you find the center frequency for the CW filter the MFJ 784B is equipped with a CW spotting tone The spotting tone marks the center frequency of the tunable CW filter but will not work in a memory CW filter While the spotting tone is present the bandwicth of the CW filter is opened to maximum allowing you to zero in on any CW signal from 300 Hz to 1000 Hz As the spotting tone pitch adjusted with the Tunable Filters left knob gets close to matching the incoming CW signal s tone you will hear a beat note This note will decrease in pitch until a very slow waver or fade is heard in the signals When this wavering is adjusted to the slowest rate the center frequency of the CW filter matches the incoming CW signal To use the CW spotting tone 1 Select the CW Filter The Filters switch must be turned to CW and the Memory button must be out 2 Engage the filter by pressing and locking the DSP button in 3 Press and hold the Program button to activate the spotting tone 4 Use the Tunable Filters left knob to zer
5. Auto Notch button in The interference should disappear or be greatly reduced Note The automatic notch will not recognize interfering tones that vary rapidly in frequency or amplitude The filter must ignore rapid amplitude and frequency changes to avoid nulling or distorting voices If the automatic notch distorts voice reduce the radio volume slightly or select a less aggressive internal auto notch jumper 6 Experiment with different filter adjustments and functions under various conditions to become familiar with the various controls Operation Error Main Document Only 5 MF 784B Instruction Manual Front Panel Description The following section will help you become familiar with the operation of the DSP The two LEDs are explained first The buttons switch and controls are then explained from left to right as they appear on the panel PWR LED This LED lights two different colors red and green It helps tell you when the DSP is on and working and whether the DSP is using the memory or the normal Tunable PreSet filters When you turn the DSP power on there will be a slight delay and this LED will light If this LED lights red the Tunable PreSet filters are being used If this LED is green the memory filters called Memory that you can store or program are being used We explain this in detail as we talk about operating the DSP If this LED does not light or does not change color when the Memory button is cha
6. Reduction Note 1 The LR HR filter becomes a band stop filter when LR is adjusted higher than HR or becomes an all pass filter when LR is adjusted equal to HR Note 2 The 2BP filter uses the bandwidth setting last used in BP filter but allows independent variation of the two center frequencies Note 3 The CW filter has an optional jumper programrmable sidetone filter Note 4 The SSB filter has its lower cutoff frequency limited to 175 Hz Note 5 The multiple automatic notch has four jumper programmable levels of aggressiveness and ables to eliminate up to four changing tones or heterodynes Note 6 The random noise reduction has a variable level of noise reduction Note 7 All FIR and IIR filter attenuations are calculated in dB a distance in Hz outside the passband All LMS filter attenuations are dependent on the characteristics of the noise Note 8 All FIR filters are linear phase with a 23 mS time delay and have the upper cutoff frequency limited to 3900 Hz 57 dB 975 Hz LM uo Introduction Error Main Document Only 7 MF 784B Instruction Manual FIR Finite Impulse Response IIR Infinite Impulse Response LMS Least Mean Square Introduction Error Main Document Only 8 MFJ 784B Instruction M anual Unit Specifications General Specifications Processor Analog Devices ADSP 2105 Data width 16 bits Clock speed 12MHz Bypass The MF 784B DSP filter has a direct audio bypass when power switc
7. an in depth description of the front panel controls refer to Chapter 3 Operation Introduction Error Main Document Only 5 MFJ 784B Instruction Manual Back Panel Layout Power Headphones Out Speaker Out Filtered Audio Adjust Filtered Audio Out Receive Audio Adjust Receive Audio In To Radio To TNC 10 16 Vdc 5 amp peak low Z audio load 1 4 stereo or mono phone jack 3 5 mmstereo or mono phone jack screwdriver adjustable potentiometer RCA phono jack 41 5 V PP 600 ohms screwdriver adjustable potentiometer RCA phono jack 5 pin DIN jack TNC xmit audio ground PTT receive audio in T R 5 pin DIN jack TNC xmit audio ground PTT filtered audio out For an indepth description of the back panel connections refer to Chapter 2 Installation Introduction Error Main Document Only 6 MFJ 784B Instruction M anual Filter Specifications BW 30 2100 Hz Lei Attenuation Type 57 dB 75 Hz 47 dB 960 Hz 47 dB 960 Hz 47 dB 960 Hz fc 300 1000 Hz BW 30 700 Hz fc 600 1700 Hz BW 1000 2500 Hz J umper Programmable 47 dB 960 Hz FIR Fixed L050 1350 Hz and 1450 2350 Hz 45 dB 960 Hz FIR Manual Notch fl 150 3400 Hz f2 150 3400 Hz 40 dB 995 Hz Manual Notch CW mode fl 300 1000 Hz f2 300 1000 Hz 40 dB 105 Hz Multiple Automatic Entire freq range of the received audio Up to 50 dB Notch Random Noise Entire freq range of selected band pass filter Up to 20 dB LMS
8. and adjust your radio for normal pitch and volume Press and lock the DSP button in Adjust the Volume control on the DSP to a comfortable volume setting Note Always use the DSP s volume control to adjust the volume when the DSP is on unless specifically told otherwise 1 Observe the Input Level LED and adjust audio input if the LED is not fully green without ever flashing red The ideal adjustment point is when the LED is as green as possible without ever flashing red If the LED is red reduce the receiver s volume control if the LED is not lit increase the receiver s volume control Refer to page 2 4 2 Adjust the left Tunable Filters control center frequency or fc and the right Tunable Filters control bandwidth or BW to peak the SSB signal for maximum intelligibility Operation Error Main Document Only 4 MFJ 784B Instruction M anual 3 You should notice the signal becomes clearer less noise and QRM as the bandwidth right Tunable Filters control is moved clockwise and the center frequency left Tunable Filters control is re adjusted At some point decreasing the bandwidth will make the signal less intelligible If this happens turn the right Tunable Filters control counter clockwise 4 Place the DSP button in the out position Adjust the receiver until you find a frequency that has CW or any other tone interference audible with a SSB or voice signal 5 Place the DSP button in the in position Lock the
9. and use it to record your PreSet and memory filters settings Use the Talk function to get the frequency values for CF BW and or LR HR PreSet RTTY Mode Mark Space Baud Rate PreSet AMTOR Mode MarkSpace Baud Rate Memory 1 Mode Operation Conditions Radio Frequency Pre Set HF PACKET Mode Mark Space Baud Rate Pre Set PACTOR Mode MarkSpace Baud Rate Memory 2 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 3 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 4 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 5 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 6 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 7 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 8 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 9 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 10 Mode Operation Conditions Radio Frequency CF BW LR HR Appendix A 8 CF BW LR HR MFJ 784B Instruction M anual NOTES Appendix A 9 MFJ 784B Instruction Manual NOTES Appendix A 10
10. by reducing or eliminating noise QRN and interference QRM DSP technology has existed for many years but has always been very complicated and expensive Recent advances in integrated circuits have greatly increased the processing power and reduced the size of DSP units These same advances also lowered the cost of DSP filtering making DSP technology affordable for the average amateur or short wave listener The heart of any DSP system is the digital signal processor Almost any microprocessor can perform DSP such as the one in a personal computer but only very fast or specialfunction processors perform DSP in real time A digital signal processor s commands are tailored to the type of instructions used in signal processing The use of special DSP commands allows a DSP filter function to be completed in very few clock cycles usually one The CPU in a typical personal computer would require a long set of instructions and therefore many clock cycles to perform the same function Analog Device s 16 bit 12 MHz processor the ADSP 2105 is used in the MF 784B The MF 784B DSP Filter converts the analog audio signals from your receiver to digital information This conversion is achieved by sampling the audio signal many thousands of times per second with an analogto digital converter The result is a string of digital numbers that represent the amplitude and frequency of the analog input signal The ADSP 2105 chip then processes the digital in
11. f1 of one 200 Hz filter and the Tunable Filters right knob controlling the center frequency f2 of a second 200 Hz filter Typical Dual Band pass Filter Response Frequency Hz 0 500 1000 1500 2000 2500 3000 3500 4000 0 10 20 30 40 dB 50 V 60 80 Filter Description 5 5 MFJ 784B Instruction Manual CW Filter 4 Use CW Filter Narrow FSK Passes razor sharp to medium frequency width The CW filter is an adjustable band pass filter that can be varied over the normal frequency range preferred by most CW enthusiasts The center frequency or pitch is controlled by the Tunable Filters left knob and has a frequency range of 300 Hz to 1000 Hz This control functions similarly to the pass band tuning or the IF shift control of a receiver with this filter The Tunable Filters right knob adjusts the filter bandwidth from 30 Hz to 700 Hz This knob acts exactly like the selectivity control on a receiver Note that as the bandwidth of this filter approaches the on off rate of the dot and dashes some ringing may appear This is an inherent characteristic of any filter when the bandwidth approaches the on off rate When this filter is operated using a very narrow bandwidth some ringing or softening is inevitable To minimize ringing use the maximum bandwicth possible CW Sidetone Filter Use To pass CW sidetone Passes any Signal very near programmed center frequency Note This is not the preferred method for pass
12. little practice you will become very good at adjusting the filter Operation Error Main Document Only 3 MF 784B Instruction Manual 4 Place the DSP button in the out position Tune your receiver until a frequency is found with several CW signals sending at the same time When the digital processing is activated by pressing the DSP button in you should be able to separate the signals with the Tunable Filters controls Careful adjustments to the DSP filter s center frequency with moderate or low bandwidth may even allow you to copy signals that were undetectable without the filter 5 Take some time to experiment with the Noise Reduction AGC Manual Notch and the Tunable Filters controls in the CW mode For the best use of this filter you should become familiar with the effects of all these controls Note Most people monitor their sending with a transmitter sidetone oscillator If you use this common method of monitoring yourself you have to program a sidetone filter or ground the T R line to monitor yourself Page 2 5 gives details on this requirement SSB and other voice modes Operation The example in this section demonstrates the basic SSB filter functions and allows for further confirmation of the station receiver audio level adjustments Turn the DSP s Filters switch to SSB mode and place the AGC and NOISE REDUCTION buttons out off Place the DSP button in the out position Tune in a SSB AM or FM station
13. narrow range of frequencies or tones The manual notch operates in every filter mode except when the DSP button is out The manual notch is often used to notch out one or two unwanted tones on CW woice or digital modes A manually adjusted notch is the only type of notch that operates correctly on CW and digital modes The manual notch can also remove warbling or buzzing carriers that the automatic notch may ignore The manual notch also causes less audio distortion in voice modes than an automatic notch A manual notch does some things better than the automatic notch In tone modulated modes the automatic notch wouldn t know which tone you wanted to hear and which tone was the interference It would remove the good signals right along with the bad signals Since the operator can tell which tones are not wanted the operator can adjust the manual notch to remove them The Tunable Filters left and right knobs adjust the frequency of each notch over the entire audio range of the filter The manual notch bandwicth is very narrow Tones within 100 Hz of each notch frequency will be reduced over ten thousand times in volume If you only need to notch one tone set the other Tunable Filters control to any end of its range Doing so will prevent the unused notch from hurting the quality of the signal you want to hear One thing is a little tricky when using the manual notch Since the manual notch uses the Tunable Filters left and right knobs to adjus
14. of the two individual filters The filter actually changes its center frequency and bandwidth settings so that the two indivdual filters are effectively implemented as a single filter The new center frequency fc is at the center of the lowest cutoff frequency and the highest cutoff frequency of the two individual filters fc lowest cutoff freq highest cutoff freq 2 The new bandwidth BW is equal to the sum of the two individual filters bandwidths BW 1 and BW2 minus the overlapped region BW BW1 BW2 overlapped region Overlapped filters are not noticeable by the operator However when using the Talk feature an operator may notice a difference in the front panel controls and the Tunable Filters left and right knob settings Overlapped filters can only occur in the following filter modes 2BP and CW with sidetone filter enabled For example The Filters switch is set to 2BP The Tunable Filters left and right knobs are set at center frequencies of 2000 Hz and 2400 Hz respectively The bandwidth of each filter is 600 Hz In this case the upper cutoff frequency of the first filter is 2300 Hz and the lower cutoff frequency of the second filter is 2100 Obviously the two filters overlap each other by 200 Hz therefore the DSP implements these two filters as a single bandpass filter When the Talk feature is used the DSP will send the following 2BP CF 2200 BW 1000 Filter Description 5 12 MFJ 784B Instruction Ma
15. red red is too high off is too low Fast Start 1 MFJ 784B Fast Start 5 Howto operate the CW filter If you work SSB skip to step 6 a Your radio should still be tuned to a CW station and setup as in step 2 except Power Press and lock the DSP button Adjust the DSP s volume control Press and hold the red Program button You will hear a spotting tone at the center frequency of the CW filter Adjust the left Tunable Filters control center frequency or fc until the tone is the same pitch as the CW station When the tones are closely matched release the Program button Slowly adjust the right Tunable Filters control bandwidth or BW clockwise The CW station s signal should become clearer less noise and QRM With practice you will be able to tune in signals without using the spotting tone You will also be able to separate multiple signals and copy signals that were undetectable without the filter Experiment with the Noise Reduction AGC and Manual Notch controls 6 Howto operate the SSB filter If you work CW skip to step 7 a Your radio should still be tuned to a SSB station and setup as in step 2 except Power Press and lock the DSP button Adjust the DSP s volume control Adjust the right Tunable Filters control bandwidth or BW clockwise to make the SSB signal clearer less noise and QRM while not making the signal less intelligible Adjust the left Tunable Filters control center frequency
16. the Input Level LED on the front panel flashes mostly green and never red Note Some compromise may be required if the receiver does not maintain the same audio level on different modes Set the Receive Audio Adjust on the DSP for the most common mode and use the receiver s volume knob to properly adjust the level when switching modes Increasing Headphone Audio Level The MFJ 784B headphone level is attenuated as it comes from the factory If the speaker audio is at a comfortable level and the headphone audio is too quiet the headphone volume can be raised by using jumpers J MP 9 and J MP 10 nex to the headphones jack Warning Do not short J MP 10 when using a mono phone plug or damage to your unit will result To raise the headphone audio level for mono headphones put a 470 ohm or smaller resistor on J MP 9 For stereo headphones put another 470 ohm or smaller resistor on J MP 10 Installation Error Main Document Only 4 MFJ 784B Instruction M anual Passing Sidetone You may perfer to listen to a station with different pitch than the sidetone of your transmitter In this situation the DSP filter will attenuate the sidetone and you will not be able to monitor your sending There are two methods of passing sidetone through the DSP filter T R Connection The preferred method for passing sidetone is the use of the T R transmit receive line on the DSP s To Radio port All filter functions are bypassed when the T
17. the MFJ 1315 is available from MFJ The voltage should be 10 16 Vdc f the power supply voltage drops below 10 volts the MFJ 784B will perform erratically Warning Voltages greater than 18 volts or reverse polarity ma permanently damage the MF 784B Headphones Out This jack supplies volume controlled audio for headphones It accepts standard male 1 4 inch stereo or mono phone plugs and provides audio to both stereo and mono headphones Speaker Out This jack supplies volume controlled audio for a speaker with a 3 5 mm stereo or mono phone plugs Disengaging the Speaker button disables this jack Filtered Audio Adjust This adjustment varies the level of the audio outputs to Filtered Audio Out and pin 4 of the To TNC port Filtered Audio Out This jack supplies line level audio for tape recorders or audio amps It is a standard RCA phono jack A quality shielded cable should be used for connections to this jack The output is dependent on the Filtered Audio Adjust and independent of the DSP s volume control Receive Audio Adjust This adjustment controls the sensitivity of the Receive Audio In jack and pin 4 of the To Radio port Proper adjustment is achieved if the Input Level indicator flashes mostly green and never red when the receiver s volume is at normal levels Refer to page 2 4 Receive Audio In This jack is normally connected to the receiver s speaker or headphones output It is a standard RCA phono jack A shielded cabl
18. 2 Test the Filters switch by turning it to each position LR HR BP 2BP CW SSB RTTY HF PACKET AMTOR PACTOR and SSTV FAX WeFAX The LEDs should blink green once after each turn of the switch 13 Test the left Tunable Filters knob by turning it to full counter clockwise then to full clockwise The LEDs should blink green once at each end 14 Test the right Tunable Filters and Noise Reduction knobs in the same way The LEDs should blink green once at each end 15 Test the jumper connections by placing plugin jumpers on the L positions of MP1J MP7 J MP8 is not used Important Performing the next step will reset the CW sidetone and the Pre Set data filters to factory defaults as described on page 4 11 If you do not want these filters to reset to factory defaults stop this selftest now by releasing the Power button Appendix A 2 16 17 18 MFJ 784B Instruction M anual Test the T R line by shorting pin 5 of the To Radio connector to ground for approximately one second or until the LEDs blink If it is shorted for less than one second the DSP might signal a false failure The filter EEPROM memory IC U8 is then tested without assistance Note that this step will reset the CW sidetone and the PreSet data filters to factory defaults If you ve pressed the buttons turned the switch and the knobs placed the jumpers and grounded the T R sense line in the correct order and the unit is working properly th
19. A 3 MFJ 784B Instruction Manual In Case of Difficulty If you experience low volume hum only when the DSP volume control is high or distortion Double check the wiring used to connect the DSP to the receiver s speaker and headphones jacks The wiring can be tested by turning the DSP off When the DSP power switch is in the off position the audio input jack is connected directly to the DSP s speaker and headphones jacks If the DSP is properly connected and the wiring is good the volume level and audio quality should be exactly the same as when the speaker or headphones is plugged directly into the receiver s speaker or headphones jacks If the DSP fails to process properly when using the Automatic Notch or Noise Reduction or if the DSP audio is distorted intermittently The receiver s volume or the DSP s level control may need to be adjusted Check the Input Level LED If you hear hum at high or low volume The power supply you are using may not be filtered properly If the DSP won t start or shuts off intermittently The power supply may not be within the required 10 16 volt range If the power supply drops below 10 volts from poor regulation or a bad connection the DSP may operate erratically An indication of poor power is the power LED flashing from red and green Technical Assistance If you have any problem with this unit first check the appropriate section of this manual If the manual does not reference your probl
20. Features Error Main Document Only 6 2BP e Normal filter e Overlapped filter ON e Filter without sidetone e Filter with CW sidetone e Overlapped filter SSB e Normal filter RITY e 21252295 Hz45 baud HF PACKET e 21252295 Hz 300 baud AMTOR e 21252295 Hz 100 baud PACTOR e 21252295 Hz 200 baud SSTV EAX WeFAX e Non adjustable Manual Notch e Manual Notch On when off MN is not sent Automatic Notch e On with aggressive level 3 when off AN is not sent Noise Reduction e On with control midrange when off NR is not sent MFJ 784B Instruction M anual 2BP CF 300 BW 30 CF 3400 BW 30 2BP CF 1000 BW 100 CW CF 700 BW 30 CW CF 400 BW 50 CF 700 BW 30 CW CF 600 BW 100 SSB CF 900 BW 1000 RTTY CF 2210 BW 250 PCKT CF 2210 BW 504 AMTR CF 2210 BW 304 PCTR CF 2210 BW 404 SSTV 1050 1350 1450 2350 MN L 150 R 3400 AN 3 NR 5 The digital filter cannot exceed the MF 784B design frequency range of 0 3900 Hz or 175 Hz minimum bandwidth in SSB See the Limited Filters section in Chapter 5 Please remember the analog circuitry begins to roll off at 250 and 3100 Hz An overlapped filter occurs when two bandpass filters overlap each other This results in a single filter that passes the entire frequency range of both filters See the Overlapped Filters section in Chapter 5 Advanced Features Error Main Document Only 7 MF 784B Instruction Manual umper Settings Sever
21. HF PACKET AMTOR PACTOR and SSTV FAX WeFAX The noise reduction filter uses adaptive and manually adjustable algorithms to provide up to 20 dB noise reduction The amount of noise reduction is adjustable with a front panel control Introduction Error Main Document Only 3 MFJ 784B Instruction Manual Block Diagram Introduction Error Main Document Only 4 Front Panel Layout AGC button Program button Memory button Filters switch PWR LED Input Level LED Tunable Filters left knob Manual Notch button Tunable Filters right knob Auto Notch button Noise Reduction knob Noise Reduction button Volume control Speaker button DSP button Power button MFJ 784B Instruction M anual Enables the autornatic gain control Press to program mernory filters to talk or to activate CW spotting tone Selects either normal or memory filters Selects one of ten normal or memory filters Indicates normal red or memory green filters Indicates input signal level red too high off too low green is OK Adjusts tunable filters and manual notch Enables the manual notch Adjusts tunable filters and manual notch Enables the autornatic notch Controls the level of noise attenuation Enables the noise reduction Controls the output volume level to speaker and headphones jacks Enables the speaker jack Enables digital processing of input signal Applies power and places the DSP imine For
22. Hz The Tunable Filters left knob varies the center frequency fc between 300 Hz and 3400 Hz This adjustment is very much like the pass band tuning or IF shift control on high quality receivers For example If the center frequency fc is adjusted to 2200 Hz and the bandwidth BW is adjusted to 600 Hz all frequencies between 1900 Hz and 2500 Hz will pass All frequencies not in the 600 Hz bandwidth will be attenuated Typical Band pass Filter Response Frequency Hz 0 500 1000 1500 2000 2500 3000 3500 4000 0 10 20 30 40 dB 50 60 70 80 Filter Description 54 MF 784B Instruction M anual 2BP Filter 3 Use Custom Voice FSK Dual Pitch CW Filter Passes 2 independent narrow to wide frequency ranges This position allows the use of two frequencyindependent variable bandpass filters in parallel The Tunable Filters left and right knobs control the individual center frequencies f1 amp f2 of the filters Each filter has the same bandwidth The 2BP position uses the bandwidth setting from the BP filter The bandwidth can be adjusted by switching to the BP position and adjusting the Tunable Filters right knob For Example To adjust the bandwidth of the 2BP filter the Tunable Filters right knob is adjusted to 200 Hz bandwidth while Filters switch is in the BP position The Filters switch is then turned to 2BP Now two filters are available with the Tunable Filters left knob controlling the center frequency
23. Operation To install and use the MF 784B in the simplest way possible follow the steps below On some steps we give you a choice of CW or SSB Choose one throughout this Fast Start section SSB also works with AM and FM voice 1 2 Install the unit Follow the installation diagram on the facing page Set the controls as follows Control Position Meaning AGC button out AGC off Program button N A N A Memory Normal button out Tunable Pre Set Filters switch CW or SSB CW or SSB filter Tunable Filters left knob center middle center freq Manual Notch button out manual notch off Tunable Filters right knob full counter clockwise widest bandwidth Auto Notch button Noise Reduction control Noise Reduction button Volume control Speaker button DSP button Power button out full counter clockwise out full counter clockwise in out out auto notch off minimum reduction noise reduction off minimum volume speaker on DSP bypassed MFJ 784B off Apply external power and press and lock the DSP s Power button The PWR LED on the front panel should light red Memory Normal Filters button Set the input level a Tune your radio to a CW or SSB station b Set your radio s volume control to a normal level If it is green press the C Use a screwdriver to adjust the Receive Audio Adjust on the back panel of the DSP until the Input Level LED front panel flashes mostly green and never
24. Power button is off out this switch connects all the input ports to the speaker and headphones outputs The Filtered Audio Out jack and the To TNC port become dead See the block diagram on page 1 4 Do not use this switch to bypass the DSP Use the DSP button You should only use this switch to turn the DSP off after you are completely finished using the DSP Operation Error Main Document Only 13 MFJ 784B Instruction M anual 4 Advanced Features Contents of This Chapter gt Memory Filters Page 4 2 Saving Memory Filters Page 4 2 gt CW Spotting Tone Page 44 Measuring Frequency Page 44 gt Talk Page 4 5 Talk Operation Page 45 gt J umper Settings Page 4 8 Talk Settings Page 4 8 Auto Notch Aggressiveness Page 4 8 Normal J umper Settings Page 4 8 Normal J umper Settings Chart Page 4 9 Setting the CW Sidetone Filter Page 4 10 PreSet Filters Page 4 11 Data Mode J umper Settings Chart Page 4 12 Advanced Features Error Main Document Only 1 MF 784B Instruction Manual Memory Filters The MF 784B allows you to save your favorite filter settings into one of ten memory filters in non volatile memory Whenever you have to repeatedly set your DSP filter for similar operating conditions you may choose to save the settings in memory Each position of the Filters switch can select a memory filter for a total of ten filters These filters are selected when the Memory button is in The memory filters store t
25. R line is pulled low The transceiver s sidetone and audio monitoring functions will appear at the DSP output without digital filtering The T R line should be connected to an output from your radio that is pulled low when the radio goes into the transmit mode such as an output for an external RF amplifier Radio manufacturers call such a line many different names Relay or RLY NO or normally open xmit transmit or send or maybe even PTT If a linear amplifier is connected to the T R line a diode 1N4001 or equivalent should be connected from the linear amplifier s control relay jack to the T R line This diode prevents the amplifier from loading the DSP s T R line when the amplifier is turned off The anode of the diode should be connected to the amplifier and the cathode banded end to the T R line Refer to the diagram on 2 3 Warning Never connect the T R line to negative voltages or to positive voltage sources that exceed 35 volts The DSP has internal protection circuitry to help prevent other equipment connected to the T R line such as a linear amplifier from damaging the unit Installation Error Main Document Only 5 MFJ 784B Instruction Manual CW Sidetone Filter The less preferred method for passing sidetone involves programming a special internal CW sidetone filter The CW sidetone filter is a totally separate jumper programmed constant frequency filter This option makes the DSP function with two se
26. WeFAX position the following filters not those stored in mernory are reset to the factory defaults as AMTOR 2125 2295 Hz PACTOR 21252295 Hz CW Sidetone Set to OFF Advanced Features Error Main Document Only 11 MF 784B Instruction Manual Data Mode J umper Settings Chart 1 2 3 4 Shift Tot yt 12153385 2070 pe pepe Pa PY 2275 1445 Hz 170 pe Pe PRP ef o o 1415 1585 Hz 170 pepe PAP AR PO 16151785 Hza 70 Pe PAP epee TY 2125 2295 H2 170 pe PAP ep H Tf 1200140072000 pe PAH PAE eT 12602460 Hz 200 Lefa afaj af 1430 1630 Hz 200 PH Pe Pepe tf 16001800 Hz 200 PH Pe Pepa Tf 2025 2225 Hz 200 PH Pe PAP ef J 21023102000 PH Pe PRP HR Pf 2125 2325 Hz 200 PH PAH Pep e 1275 27002 425 PH PAH Pepa Pf 21252550Hz 425 PH PAH PR Pe PT 2275 2125 Hz 850 Ladaga 22125 2975 Hz 850 5 6 7 110 Factory defaults Data filter center frequency mark space 2 Data filter bandwidth 1 2 x shift baud rate ref ARRL Handbook Advanced Features Error Main Document Only 12 Filter Description MFJ 784B Instruction M anual 5 Contents of This Chapter gt VVV VVVVVVVVVVV LR HR Filter 1 Band stop Filter BP Filter 2 2BP Filter 3 CW Filter 4 CW Sidetone Filter SSB Filter 5 RTTY Filter 6 HF PACKET Filter 7 AMTOR Filter 8 PACTOR Filter 9 SSTV FAX WeFAX Filter 10 Manual Notch Filter Automatic Notc
27. al features of the MFJ 784B are controlled by internal movable jumpers These jumpers are used for Talk sets CW tone frequency and Morse code speed Auto Notch sets aggressiveness level CW sidetone enables and sets sidetone filter Data modes programs markspace frequencies and baud rates Talk Settings The Talk routine will tell you the DSP s filter settings in Morse code J umpers 1 3 set the pitch of the Morse code J umpers 4 amp 5 set the Morse code speed The DSP is shipped with these jumpers set at 5 WPM and 700 Hz pitch Auto Notch Aggressiveness We ship the DSP in the least aggressive setting 1 If you are unhappy with the notch performance and would like to step it up a little bit you can reset the jumpers Remember that the automatic notch s distortion of voices will get worse if you choose a more aggressive setting Normal J umper Settings Except when programming CW sidetone and data filters the jumpers are set for the Talk routine and the auto notch aggressiveness settings After programming a PreSet data filter or the CW sidetone filter the jumpers should be returned to their original positions for Talk and auto notch removing the cover Even though the unit is off power is still Warning Remove all power plug from the MEI 784B before AN applied to some circuitry To set the tone frequency code speed and auto notch level Disengage turn off the Power button and remove the power plug Remove
28. baud AMTOR signals This filter can also be programmed to one of several different markspace encies and or baud rates This procedure is detailed on page 4 11 Under special conditions the operator may wish to use one of the adjustable band pass filters in place of the AMTOR filter PACTOR Filter 9 Use PACTOR Narrow Packet Wide RTTY Passes high frequency tones with medium frequency width The PACTOR filter is factory preset for best performance with standard 21252295 Hz markspace frequencies 170 Hz shift 200 baud PACTOR signals This filter can also be programmed to one of several different mark space frequencies and or baud rates This procedure is detailed on page 4 11 Under special conditions the operator may wish to use one of the adjustable band pass filters in place of the PACTOR filter SSTV FAX WeFAX Filter 10 Use Slow Scan Facsimile Passes two separate frequency ranges one narrow and one wide frequency width This filter is a dual band pass filter that allows two separate frequency groups to pass through the filter The first filter is preset to pass frequencies between 1050 Hz and 1350 Hz for the synch tone and the Vertical Interval Signal VIS tones The picture content is passed by a second filter at 1450 Hz to 2350 Hz This filter is non adjustable and cannot be programmed to different frequencies Filter Description 5 8 MFJ 784B Instruction M anual Manual Notch Filter Use Removes unwanted t
29. d out what is stored there position the controls as follows Control Position Meaning Memory button in select memory filters Filters switch 3 2BP memory filter 3 Manual Notch button out manual notch off Auto Notch button in auto notch on Noise Reduction control midrange reduction level 5 Noise Reduction button in noise reduction on Assume the Auto Notch aggressiveness is jumper set to level 3 Release the DSP button out Momentarily press the Program button The MFJ 784B would send the following Morse Code message BP CF 1025 BW 350 AN 3 NR 5 This means in memory position 3 you saved a band pass filter with a bandwidth of 350 Hz and center frequency of 1025 Hz The unit also sent the current settings for notch and noise reduction Now suppose you trymemory filter 6 Turn the Filters switch to 6 RTTY Press the Program button and the MFJ 784B sends RTTY CF 1360 BW 279 NR 5 In this position you have saved a jumper programmed RTTY filter with the center frequency of 1360 Hz and a bandwidth of 279 Hz These are the settings for European RTTY Notice that nothing sent for auto notch because it is disabled in the RTTY filter These are examples of the individual filter settings LR HR e LowReject High Reject LR lt HR LRHR 2000 3400 e Bandstop filter LR gt HR LRHR 0 1400 2200 3900 e All pass filter LR HR LRHR 0 3900 BP e Normal filter BP CF 1500 BW 2100 e Limited filter BPCF675 BW 1350 Advanced
30. e should be used to connect this connector to the station receiver To Radio This port supplies connections for transmit and receive audio PTT is connected directly to the To TNC port A connection is also available for a T R line to automatically bypass the filter during transmit To TNC This port supplies connections to the filtered audio output and the transmit audio inputs PTT is connected directly to the To Radio port Installation Error Main Document Only 2 MFJ 784B Instruction M anual Basic Connections In the most simple case the MFJ 784B will be installed in the audio path between your receiver and your headphones or speaker Installation Error Main Document Only 3 MFJ 784B Instruction Manual Setting Receive Audio Level Input Level When first connecting the DSP filter and whenever the receiver audio level changes you should check the Input Level indicator This LED indicates the input signal level As a signal is received the Input Level LED will flash from off to either green or red If the indicator flashes Mostly Green never red the input level is adjusted correctly Any Red the input level is too high Stays Off or barely green the input level is too low To set Receive Audio Adjust 1 Tune your radio to the mode you will be operating most 2 Set your radio s volume control to a normal level 3 Usea screwdriver to adjust the Receive Audio Adjust on the back panel of the DSP until
31. e unit repeatedly sends OK 784 with blinking green LEDs in Morse code A repetitive message such as B4 FAIL with blinking red LEDs indicates that you didn t follow the correct order or the unit failed the test The prefix and the number indicate the nature of the failure see table below Disengage the Power button and rernove the power plug Replace all jumpers from MP1 to J MP7 to their original positions Replace the DSP s cover 6 screws Reconnect power and resume with normal operation Prefix Number and Its Designation B1 ACC button S1 LR HR switch position B2 PROGRAM button S2 BP switch position B3 MEMORY button S3 2BP switch position B4 MANUAL NOTCH button S4 CW switch position B5 AUTO NOTCH button S5 SSB switch position B6 NOSE REDUCTION button S6 RTTY switch position D N I SPEAKER button S7 HF PACKET switch position B8 DSP button S8 AMTOR switch position B9 POWER button S9 PACTOR switch position J1 JMPI1 jumper SO SSIV FAX WeFAX switch position J 2 J MP2 jumper KI J3 J MP3 jumper K2 J4 J MP4 jumper K3 NOSE REDUCTION knob J5 J MP5 jumper K4 6 J MP6 jumper TR 7 J J TUNABLE FILTERS left knob TUNABLE FILTERS right knob VOLUME knob T R sense TO RADIO DIN pin 5 J MP7 jumper EE EEPROM IC U8 These controls are included here for completeness even though they are not directly tested by this selftest Appendix
32. eSet jumper or factory programmed filters marked LR HR through SSTV FAX WeFAX When the Memory button is in the Filters switch picks a memory location labeled 1 through 10 on the front panel The DSP processes the signal using the filter you have stored in that memory location Page 4 2 gives you more detail on the use of memory Filters Switch This switch picks the main filter used to process the signal It is used in conjunction with the Memory button we talked about above It functions whenever the DSP power is on and the DSP button is in Note Please remember that when we say Tunable the main filter s bandwidth and frequencies can be adjusted by the two front panel Tunable Filters controls PreSet means the front panel Tunable Filters controls cannot be used to adjust the filter A Pre Set filter s markspace frequencies and bandwidth can only be changed by removing the cover and re programming internal jumpers see page 4 11 When the Memory button is out the Filters switch selects one of the 5 Tunable filters LR HR BP 2BP CW and SSB or one of the 5 Pre Set filters RTTY HF PACKET AMTOR PACTOR and SSTV FAX WeFAX When the Memory button is in the Filters switch selects any one of ten memory filters you have stored in locations 1 through 10 of the DSP s memory The Filters switch also selects the memory position 1 10 where you can store the last Tunable PreSet filter you re using Chapter 5 Filter Desc
33. em or your problem is not Solved by reading the manual you may call MFJ toll free at 1 800 647 TECH 8324 Outside of the continental U S A call 601 323 5869 You will be best helped if you have your unit manual and all information on your station handy SO you can answer any questions the technicians may ask You can also send questions by mail to MFJ Enterprises INC PO Box 494 Mississippi State MS 39762 by FAX to 601 323 6551 or on Compuserve at 76206 1763 Compuserve com Send a complete description of your problem an explanation of exactly how you are using your unit and a complete description of your station Appendix A 4 MFJ 784B Instruction M anual MEI Prewired Cables and Open End Cables The following MFJ radioto TNC cables are prewired for most 8 pin rigs and HTs The open end cables allow you to make your own cables For your nearest dealer or to order call toll free 800 647 1800 Pre wired Radioto DSP Cables MFJ Part Icom 8 pin modular Note 1 Does not include IC W2A Note 3 Does not include 25A 255A Note 2 Does not include 2500 Note 4 Does not include IC 100H IC2700H Pre wired DSP to TNC Cables MFJ Part All MEI TNCs PK 900 PK 96 PK 12 PacCony MFJ 5100 14 95 other TNC 2 compatibles KAM HF KAM VHF KPC3 KPC9612 Note 5 YH for KAM HF port YV for KAM VHF port Cther Kantronics use YV models Note 6 YH models for KPC9612 9600 baud port Note 7 YV for KPC9612 1200 baud po
34. es or steady tones and instantly removes them It is so good it can remove four drifting tones at the same time even if the tones are moving in different directions The automatic notch filter has two important limitations First it cannot tell the difference between a good tone and a bad tone Some Filter positions are used for receiving tone signals and the auto notch wouldn t have any idea which tone you really want to copy Therefore we can t let you use the auto notch in the following Filters switch positions CW RTTY HF PACKET AMTOR PACTOR and SSTV FAX WeFAX In these modes the auto notch would remove every signal not just the bad ones Second the automatic notch cannot tell the difference between a voice and a tone that varies rapidly in volume and pitch If we made the automatic notch remove all the very fast changing tones it would also remove tones from voices If we made the automatic notch work only on the slowest changing tones it would not follow the drifting or fading tones you didn t want to hear Because of this limited operating range we give you two ways to select how quickly and completely the automatic notch works One way you can control the notch speed is by reducing the volume control on your receiver slightly This will lower any distortion on voices while the automatic notch is being used The second way to adjust the automatic notch involves removing the DSP s cover and moving two jumpers to different p
35. formation with different digital filter algorithms depending on the settings of the front panel controls The end result is a digitized signal with undesired signal components either reduced or removed and desired components enhanced The processed digital signal information is converted backto an audio signal by a digital to analog converter and sent to the audio amplifier and line level outputs Introduction Error Main Document Only 2 MFJ 784B Instruction M anual Product Overview The MF 784B tunable DSP filter is a highly selective audio filter suitable for most amateur applications The MF 784B contains 5 tunable filters 5 pre set filters a tunable manual notch an autornatic notch filter and an adaptive noise reduction filter Filter settings can be saved into one of ten memory filter positions The 5 tunable filters consist of the following LR HR Low Reject High Reject BP Band pass 2BP Double band pass CW CW mode band pass SSB SSB mode band pass The 5 preset data filters are band pass filters programmed with jumpers for the different data modes mark space frequencies and baud rates RTTY HF PACKET AMTOR PACTOR SSTV FAX WeFAX The tunable manual notch filter attenuates 2 tones manually with the front panel controls The auto notch filter attenuates up to 4 tones automatically The automatic notch will attenuate moving or shifting tones The automatic notch is disabled in the following modes CW RTTY
36. h Filter Noise Reduction Filter Limited Filters Overlapped Filters Page 5 2 Page 53 Page 54 Page 5 5 Page 5 6 Page 5 6 Page 5 7 Page 5 7 Page 5 7 Page 5 8 Page 5 8 Page 5 8 Page 5 9 Page 5 10 Page 5 10 Page 5 11 Page 5 12 Filter Description 5 1 MFJ 784B Instruction Manual The following section describes the filters available in the various Filters switch positions in detail All graphs of the following filters show a line at the noise floor of 55 dB The response for these digital filters is typically much deeper than 55 dB but circuit noise will generally mask any response below that point LR HR Filter 1 Use Custom Voice FSK Wide CW Filter Passes medium to wide frequency wicth This position selects an adjustable low reject high reject filter The low reject filter Low removes all signals below a user selected frequency The low reject filter cutoff frequency can be varied between 200 Hz and 2200 Hz with the Tunable Filters left knob The high reject filter High removes all signals above the selected frequency The high reject limit is adjustable between 1400 Hz and 3400 Hz with the Tunable Filters right knob For example If the low reject filter is adjusted to 900 Hz and the high reject filter is adjusted to 2500 Hz all frequencies below 900 Hz and above 2500 Hz will be rejected In this case the DSP filter will only pass frequencies from 900 Hz to 2500 Hz Typical Low Reject High Reject Filter Resp
37. h is in off position Input Output Specifications Power The maximum current demand will be less than 500 mA at maximum volume but will always be more than 175 mA Filtered Audio Out This jack provides approximately 1 5 volts P P into 600 ohm or higher impedance loads The output voltage of this jack is dependent on Filtered Audio Adjust Receive Audio In This jack should be driven in a range of 1 to 2 8 volts P P when Receive Audio Adjust is set to maximum sensitivity When Receive Audio Adjust is set to minimum sensitivity the DSP requires a very high input voltage Input circuit loading is 10 K ohms nominal Audio Output Audio output power is 2 5 watts into a 6 ohm load with the MFJ 1315 power supply Audio frequency response is from 250 to 3100 Hz 3 cB Introduction Error Main Document Only 9 MFJ 784B Instruction M anual 2 Installation Contents of This Chapter gt Back Panel Connections Page 2 2 gt Basic Connections Page 2 3 Setting Receive Audio Level Input Level Page 24 Increasing Headphone Audio Level Page 2 4 gt Passing Sidetone Page 2 5 T R Connection Page 25 CW Sidetone Filter Page 2 6 gt DSP to TNC Connections Page 2 6 Installation Error Main Document Only 1 MFJ 784B Instruction Manual Back Panel Connections Power This connector supplies power to the unit It connects to a 2 1 mm coaxial plug with the center conductor positive and the shield ground An optional dc supply
38. he Filters switch s Tunable PreSet filter selection and the corresponding filter s center frequency and bandwidth or lower and upper cutoff frequencies including the CW sidetone filter if set and enabled The center frequency and bandwidth or low high reject frequencies of the fillers stored in memory cannot be adjusted Only the noise reduction and notch filters can be adjusted while using a memory filter Memory button in If you use several different mark space frequencies program and save several filters while the cover is off Otherwise you will have to take the cover of the unit off several times Save a memory filter with each markspace frequency that you will be using For programming markespace frequencies refer to page 4 11 It is not necessaryto erase an old mernory filter Old filters are erased when a new filter is saved over them Use the chart on page Ae to record your memory filters settings Saving Memory Filters 1 With the Memory button out select and adjust the filter that you want to save Advanced Features Error Main Document Only 2 MFJ 784B Instruction M anual 2 Press and lock the Memory button in The PWR LED will now turn green indicating the memory filters and your new filter settings will be saved temporarily until they are saved into a memory position 1 10 Note From steps 2 4 your filter may not appear to work because the filter position 1 10 is still set to the old mernory filter 3
39. ing sidetone This filter will pass unwanted signals within 30 Hz of the sidetone frequency See page 2 5 Passing Sidetone The CW sidetone filter is a constant frequency filter used to pass sidetone through the DSP It makes the unit operate as two separate parallel filters one normal tunable or memory CW filter and the other a constant frequency sidetone filter The CW sidetone filter is set at 50 Hz bandwidth The filter is jumper programmable to center frequencies from 300 Hz to 1000 Hz in 50 Hz increments Filter Description 56 MFJ 784B Instruction M anual SSB Filter 5 Use All Voice modes FSK CW Filter Passes medium to wide frequency width The SSB filter is a bandpass filter with adjustable center frequency and bandwidth The center frequency fc is adjusted with the Tunable Filters left knob in a range of 600 Hz to 1700 Hz The Tunable Filters right knob adjusts the bandwidth BW from 1000 Hz to 2500 Hz The actual filter response is limited internally to a minimum of 175 Hz While some voice transmissions may be understandable with only 1000 Hz of bandwidth if the center frequency is properly adjusted the majority of stations will be copied best with the controls nearly centered The optimum center frequency and bandwidth setting will be determined by the transmitting operator s voice the transmitter s response the receiver s response any noise or QRM and or the receiving operator s hearing The operato
40. is button in If the DSP is on and operating pushing the AGC button in will make every signal have nearly the same volume level if the input signal level changes less than 18 dB If there is a lot of noise on the signal you may not want to use the AGC function It will increase the volume of the noise during long pauses in the signal you are listening to That can distract you or make it difficult to concentrate on the signal you are listening to Program Button This button is used to make the DSP memorize the filter settings you are currently using When using the tunable CW filter this button activates the CW spotting tone It also starts a Talk feature if the DSP button is out This button does not stay locked in like the other buttons it springs right back out when released The use of this button is very special To use this button to memorize or save a filter please read the section on page 4 2 To use this button to activate the spotting tone please read the section on page 4 4 To use this button to start the Talk feature please read the section on page 4 5 Operation Error Main Document Only 7 MFJ 784B Instruction Manual Memory Button This button allows you to choose two different groups of filters with the Filters switch This button functions any time the DSP s power is on and the DSP button is in With the Memory button out the Filters switch picks one of ten Tunable front panel adjustable and Pr
41. le Filters control is centered and the right control is fully counter clockwise Note Always use the DSP s volume control to adjust the volume when the DSP is on Never adjust the receiver s volume knob to control the volume unless the DSP s power is off 1 Look at the Input Level LED If it flashes or lights red you will have to decrease the receiver s volume control or adjust the Receive Audio Adjust control on the DSP s back panel towards MIN If the Input Level LED is flashing or steadily green the audio level is acceptable The ideal setting is where the LED is as green as possible without ever turning red Refer to page 2 4 for a longer explanation 2 Press and hold the red Program button You will hear a tone Adjust the left Tunable Filters control center frequency or fc until the tone is the same pitch as the CW station When the tones are closely matched release the button 3 Slowly adjust the right Tunable Filters control bandwidth or BW clockwise This will increase the selectivity The desired signal should become clearer less noise and QRM as the right control is moved clockwise If turning this control makes the desired signal disappear the left Tunable Filters control fc will have to be re adjusted Please go through steps 2 and 3 several times to get a feel for how the controls act You will notice tuning becomes more touchy as the BW bandwidth control is decreased but the signal becomes clearer With a
42. nged the DSP is not operating correctly Input Level LED This LED lights two different colors red and green It tells you if the DSP is getting the correct audio level from the receiver The volume of the audio from your receiver will change with different signals Please remember that sometimes there may be a lot of receiver audio and sometimes there may not For example the station you are listening to will probably not be sending all the time or may be fading in and out Operation Error Main Document Only 6 MFJ 784B Instruction M anual The function of this LED is very simple When you are listening to a norrnal signal the LED should light the most steady and brightest green possible without ever going red If the LED doesn t light consistently green or lights red on normal signals the receiver volume or the DSP s Receive Audio Adjust is out of adjustment for the optimum filter performance Initially set Receive Audio Adjust refer to page 2 4 and then touch up the receiver s volume control to keep the input level at the optimum setting AGC Button This button controls an automatic gain control AGC program The AGC program automatically adjusts the DSP s internal gain It tries to make all signals have exactly the same volume The AGC button setting cannot be stored in memory It operates independently of all other buttons and controls except the DSP and the Power buttons The AGC is activated by pushing and locking th
43. nual A Appendix Contents of This Appendix gt SelfTest Page A 2 gt In Case of Difficulty Page AA gt Technical Assistance Page A4 gt MH Prewired Cables and Open End Cables Page A5 gt PreSet and Memory Filters Settings Chart Page A6 Appendix A 1 MFJ 784B Instruction Manual Self Test This selftest is used to test all the digital circuitry switches and controls of the MEI 784B To perform the selftest 1 Turn the Filters switch to BP 2 Pushall buttons so they are in the out position 3 Turn all knobs to full clockwise except Volume Set Volume to a comfortable listening level 4 Disengage the Power button and remove the power plug 5 Remove the DSP s cover 6 screws 6 Remove all jumpers from J MP1 to J MP7 Record their positions to re configure the unit after the selftest 7 Reconnect power 8 Press and hold the Program button 9 Press and lock the Power button to on 10 Release the Program button The unit sends SELF TESTin Morse code at 10 WPM For the entire test the LEDs should blink green once after each operation If the LEDs blink red the unit fails the test and a Morse code message is sent to indicate the nature of the failure 11 Test each button except the Speaker and Power buttons by pressing AGC Program Memory Manual Notch Auto Notch Noise Reduction and DSP buttons Skip the Speaker and Power buttons The LEDs should blink green once after each button push 1
44. o DSP and the MFJ 784B The second chapter tells about the back panel and how to install the unit with a radio or TNC Chapter 3 tells how to operate the unit in CW and SSB and describes the various controls Advanced Features Chapter 4 tells how to use the special features of the MFJ 784B The last chapter is a description of the digital filters used in this unit The appendix has two important sections troubleshooting and technical assistance There is also a selftest for the unit s digital circuitry and controls Refer to these sections if you should have any problem with your new MFJ 784B Important Please read this section to become familiar with the terms and mechanics used in this manual Whenever the manual text discusses a control jack or level adjustment the name will appear in Bold Example Plug a headphone into the Headphones Out jack for The Memory Normal Filters button will be referred to simply as the Memory button throughout this manual Definitions for the abbreviations used in this manual are listed below LR Low Reject Cutoff Frequency HR High Reject Cutoff Frequency fl Center or Notch Frequency 1 f2 Center or Notch Frequency 2 fc Center Frequency BW Bandwidth FIR Finite Impulse Response IIR Infinite Impulse Response LMS Least Mean Square WPM Words Per Minute MFJ 784B Instruction M anual MFJ 784B Fast Start Fast Start Beginners Installation and
45. obeat match the spotting tone and the CW signal 5 Release the Program button 6 Decrease the bandwicth with the Tunable Filters right knob to eliminate all other signals Measuring Frequency By using the spotting tone you can measure the approximate frequency of any audio tone between 300 Hz and 1000 Hz 1 Disengage the DSP button out to bypass the filter 2 Select the CW Filter The Filters switch must be turned to CW and the Memory button must be out Engage the filter by pressing and locking the DSP button in Press and hold the Program button to activate the spotting tone Use the Tunable Filters left knob to zero beat match the spotting tone and the signal you wish to measure Release the Program button Release the DSP button Press and release the Program button Copy the CW The number following CF is the signal s approximate frequency You are using Talk See the Talk section on page 4 5 Vr W DEO Advanced Features Error Main Document Only 4 MFJ 784B Instruction M anual Talk In order to know more about the settings of the various filters MFJ has provided the Talk function Talk tells you filter settings by sending them over the audio outputs and by flashing them on the LEDs in Morse code This feature is extremely useful if you have forgotten the settings for jumper programmed memory filters and you do not wish to remove the cover to re program them When used with the CW spotting tone this fea
46. ogram it to the sidetone frequency of your radio The center frequency of the sidetone filter ranges from 300 Hz to 1000 Hz in 50 Hzincrements The bandwicth of the sidetone filter is fixed at 50 Hz See the chart below for jumper settings The DSP unit is shipped with the CW sidetone filter set to off If you wish to disable the filter program it with all four jumpers in the H position To set the CW sidetone filter 1 Disengage the Power button and remove the power plug Program button is released 9 Disengage the Power button and remove the power plug 10 JMP IJ MP IJ MPI JMP Sidetone 1 2 3 4 Frequency I Ij r r 2 Removethe unit s cover 3 Set the jumpers for the selected sidetone filter 4 TurntheFilters switch to CW 5 Reconnect the power cable 6 Press and hold the Program button 7 Press and lock the Power button to on 8 The unit will beep at the new sidetone pitch until the HIH Set the jumpers back to the Talk tone frequency and Morse code speed 11 Replace the unit s cover Cool Factory default I 12 Reconnect the power cable and resume normal operation Advanced Features Error Main Document Only 10 MF 784B Instruction M anual Pre Set Filters We have set the RTTY HF Packet AMTOR and PacTOR filters to the most commonly used markspace frequencies and baud rates If you wish to change from the factory defaults you must change the jumpers and program a filte
47. ones or heterodynes Removes up to 2 very narrow frequency ranges and passes all others The manual notch filter allows the use of two frequencyindependent manually tunable notch filters The Tunable Filters left and right knobs control the individual notch frequencies fl amp f2 The manual notch has two different frequency ranges and widths one for the CW filter and one for the other filters When using the CW filter the notch is narrower 45 Hz 240 dB and has a frequency range of 300 Hz to 1000 Hz same as the CW filter In all other modes the notch is wider 85 Hz 3 40 dB and has a frequency range of 150 Hz to 3400 Hz For Example There is RTTY in your SSB audio After engaging the Manual Notch button use the Tunable Filters left and right knobs to notch the two RTTY tones at 2125 and 2295 Hz Typical Manual Notch Filter Response Frequency Hz 0 500 1000 1500 2000 2500 3000 3500 4000 0 20 i dB 60 100 120 Filter Description 5 9 MF 784B Instruction Manual Automatic Notch Filter Use Removes multiple tones or heterodynes quickly Removes up to 4 changing tones in the presence of speech signals The multiple automatic notch filter searches for and eliminates up to four changing or shifting tones in milliseconds with attenuation as great as 50 dB All the notches are extremely narrow resulting in a minimal effect on the voice signals The automatic notch filter is disabled in the following filte
48. ons ieri e oett erit J umper Settings Talk Settings Auto Notch Aggressiveness esent Normal J umper Settings rener Normal J umper Settings Chart Setting the CW Sidetone Filter ee PreSet Filters nee Data Mode J umper Settings Chart 4 12 LR HR Filter 1 Bandstop Filter BP Filter 2 2BP Filter 3 RE ee tu hes CW Sr idc CW Sidetone Filter SSB Filter EL ueteres irre EC tica d inn rev dn E Co EE RTTY Fiter LH HF PACKET Filter 7 AM TOR Filter 8 hrn neg PACTOR Filter 9 3 232 2a SSTV FAX WeFAX Filter 10 Manual Notch nl UE Automatic Notch lgl Noise Reduction Filter leg RI soto occ nc rentia rtm cec iicet NNE Overlapped leie MFJ 784B Instruction M anual Appendix A Self Test Iesele Te A4 Technical Assistance e eseeteeteentnnttetnnttettentnnas MF Prewired Cables and Open End Cables PreSet and Memory Filters Settings Chart MF 784B Instruction Manual Before Reading This Manual This manual is divided into two parts The first part called Fast Start is meant for people who need to know nothing except how to minimally install the unit and operate it on CW and SSB The second part Chapters 1 to 5 is meant for operators who want or need more information Detailed description of the unit and its operation are described in these chapters The first chapter is an introduction t
49. onse Frequency Hz 0 500 1000 1500 2000 2500 3000 3500 4000 10 20 30 dB 40 50 60 70 80 Filter Description 5 2 MFJ 784B Instruction M anual Band stop Filter Use Rejecting broad or variable frequency signals between 1400 2200 Hz Removes medium to wide frequency width When the low reject filter the Tunable Filters left knob is adjusted to a frequency higher than the high reject filter the Tunable Filters right knob the filter removes all frequencies between the two filter settings and passes all frequencies outside the settings of the two filters This special filter is called a band stop or bandreject filter A band stop filter makes a hole in the middle of the frequency range and passes everything on either side of the hole For example If the low reject filter is adjusted to 2200 Hz and the high reject filter is adjusted to 1600 Hz all frequencies between 1600 Hz and 2200 Hz will be removed This creates a hole with a 600 Hz bandwidth Typical Band stop Filter Response Frequency Hz 0 500 1000 1500 2000 2500 3000 3500 4000 Filter Description 5 3 MFJ 784B Instruction Manual BP Filter 2 Use Custom Voice FSK Custom CW Filter Passes narrow to wide frequency wicth This filter is an adjustable band pass filter The bandwidth BW is controlled by the Tunable Filters right knob This adjustment is similar to the selectivity control on a receiver It can be adjusted from 30 Hz to 2100
50. or fc to peak the signal for maximum intelligibility Readjust the right Tunable Filters control bandwidth or BW clockwise to eliminate most of the noise and QRM At some point decreasing the bandwidth will make the signal less intelligible Press the DSP button to the out position Find another station that has CW or some other tone interference audible with a SSB or voice signal Press the DSP button to the in position and filter the voice signal Lock the Auto Notch button in Any remaining tones should disappear or be greatly reduced Experiment with different filter adjustments and functions under various conditions to become familiar with the various controls 7 Now that you have used the DSP filter you can read other parts of this manual to learn to use the other features of the MFJ 784B Fast Start 2 MFJ 784B Instruction M anual Introduction Contents of This Chapter Introduction to DSP Page 12 gt Product Overview Page 1 3 gt Block Diagram Page 14 gt Front Panel Layout Page 15 gt Back Panel Layout Page 1 6 gt Filter Specifications Page 1 7 gt Unit Specifications Page 1 8 General Specifications Page 1 8 Input Output Specifications Page 1 8 Introduction Error Main Document Only 1 MFJ 784B Instruction Manual Introduction to DSP The MEI 784B tunable DSP Filter uses stateoftheart Digital Signal Processing DSP technology Digital Signal Processing greatly improves signal clarity
51. ositions This adjustment allows you to choose four different levels of what we call auto notch aggressiveness We ship the DSP in the least aggressive setting 1 If you are unhappy with the notch and would like to step the notch performance up a little bit you can reset the jumpers Refer to J umper Settings on page 4 8 Remember that the automatic notch s distortion of voices will get worse if you choose a more aggressive setting Operation Error Main Document Only 11 MF 784B Instruction Manual Noise Reduction Control This knob controls how much the noise reduction program reduces random noises Random noises are noises that do not repeat at exactly the same rate When this control is in the full clockwise position random noises are reduced the maximum amount possible This control s setting can be used in any active filter mode including while the Memory button is in Remember to use the least amount of noise reduction necessary Turning the Noise Reduction control up too far clockwise will reduce the audio and cause unnecessary audio distortion and echo This is an unavoidable side effect of noise reduction at audio frequencies The slight echo or hollowness in voices occurs from time delays in the filter and the noise reduction program s effect on random peaks in voices Turning off the AGC on the DSP may also reduce how much unwanted noise bothers you Noise Reduction Button This button turns the noise reduction fil
52. parate parallel filters One filter is the standard adjustable CW filter and the other is the fixed frequency CW sidetone filter This method has the advantage of not requiring a T R connection but the disadvantage of allowing unwanted signals to feed through if they happen to be within 30 Hz of the sidetone frequency To enable the CW sidetone filter internal jumpers must be set to the sidetone frequency of your radio Refer to page 4 10 for a description of setting the sidetone filter The center frequency of the sidetone filter ranges from 300 Hz to 1000 Hz in 50 Hz increments The bandwidth of the sidetone filter is fixed at 50 Hz DSP to TNC Connections When connecting to a TNC MF suggests the use of the 5 pin ports TNCs need a PTT connection that is only available on these ports The MFJ 784B plugs directly into any MFJ TAPR2 compatible TNC Use a 5 pin DIN to 5 pin DIN cable MFJ 5100 for connection to MF TAPR2 compatible TNCs or the PK 12 96 900 MFJ offers prewired radio cables models MFJ 50xx for connection to your radio and pre wired TNC cables models MF 51xx for connection to other TNCs Refer to the appendix for more information on these radioto TNC cables To Radio Function To TNC Function TNC Xmit Audio TNC Xmit Audio Ground Receive Audio In Filtered Audio Out T R No Connection Installation Error Main Document Only 6 MFJ 784B Instruction M anual Installation Error Main Document Only 7
53. r You may program these filters to a number of markspace frequencies shifts and baud rates The baud rate setting controls the bandwidth of the filter Depending on conditions it is possible to run higher baud rates than are calculated The SSTV FAX WeFAX filter is fixed When you program into this position no change of the jumpers is necessary the PreSet filters and CW sidetone not those in memory filters will reset to the factory defaults See below To set markspace frequency or reset the filters to the factory defaults 1 Press and unlock the Power button to off and remove the power plug 2 Removethe unit s cover 6 screws 3 Set the jumpers for the selected data filter see jumper table on next e Record the PreSet filter settings with the chart on page A Error Bookmark not defined Turn the Filters switch to RTTY HF PACKET AMTOR PACTOR or SSTV FAX WeFAX Reconnect the power cable Press and hold the Program button Press and lockthe Power button to on The unit will beep until the Program button is released Press and unlock the Power button to off and remove the power plug 10 Set the jumpers back to the Talk tone frequency and Morse code speed and the auto notch aggressiveness level Refer to page 4 8 11 Replace the unit s cover 6 screws 12 Reconnect the power cable and resume normal operation 5 ID E SEQ Factory Filter Defaults When you program a filter to the SSTV FAX
54. r may prefer to monitor himself herself in the transmit mode Refer to the section called Passing Sidetone on page 2 5 RTTY Filter 6 Use RTTY FSK Passes high frequency tones with narrow frequency width The RTTY filter is factory preset for best performance with standard 2125 2295 Hz markspace frequencies 170 Hz shift 45 baud RTTY signals This filter can also be programmed to one of several different markspace encies and or baud rates This procedure is detailed on page 4 11 Under special conditions the operator may wish to use one of the adjustable band pass filters in place of the RTTY filter HF PACKET Filter 7 Use Packet Wide RTTY FSK Passes high frequency tones with medium frequency width The HF Packet filter is factory preset for best performance with standard 21252295 Hz markspace frequencies 170 Hz shift 300 baud HF Packet signals This filter can also be programmed to one of several different mark space frequencies and or baud rates This procedure is detailed on page 4 11 Under special conditions the operator may wish to use one of the adjustable band pass filters in place of the HF Packet filter Filter Description 5 7 MF 784B Instruction Manual AMTOR Filter 8 Use AMTOR Narrow PACTOR Wide RTTY FSK Passes high frequency tones with narrow frequency width The AMTOR filter is factory preset for best performance with standard 2125 2295 Hz markspace frequencies 170 Hz shift 100
55. r modes CW RTTY HF PACKET AMTOR PACTOR and SSTV FAX WeFAX including those stored in memory There is an adjustment to change the speed of the automatic notch filter We call this adjustment the automatic notch aggressiveness By changing a jumper setting this aggressiveness can be changed in a range of four levels See the jumper setting section on page 4 8 Noise Reduction Filter Use Removes random noises such as white noise background hiss etc Removes random noises and passes coherent signals like voices The random noise reduction filter effectively removes noises in the presence of voice with minimal degradation of the voice itself The noise reduction filter works by automatically forming constantliyvarying band pass filters around the coherent components such as speech of the audio signal In effect this provides noise reduction by reducing the individual filters bandwidths to the minimum required to pass the speech signals intelligently This filter greatly reduces operator fatigue during longterm monitoring and makes listening much more pleasant There is a noise reduction control to adjust the reduction characteristics of the noise reduction filter to prevent signal distortion When this control is in the full clockwise position random noises can be attenuated up to 20 dB depending on the types of noises Filter Description 5 10 MFJ 784B Instruction M anual Limited Filters Filter response is limited
56. ription gives more detailed information on each filter type available with this switch Chapter 4 Advanced Features gives more details on using the memory Operation Error Main Document Only 8 MFJ 784B Instruction Manual Tunable Filters Controls The Tunable Filters knobs left and right adjust the center frequency also called the tone or pitch and the bandwicth also called the selectivity or the lower and upper cutoff frequencies of the 5 Tunable filters selected by the Filters switch These filters are the LR HR BP 2BP CW and SSB filters These controls also adjust the two manual notch frequencies whenever the Manual Notch button is in Note The manual notch function uses the same controls as the main filter That means any time the manual notch is being used the adjustable filter cannot be changed The following chart tells you what type of adjustment is made by the left and right Tunable Filters controls in every front panel adjustable filter position Mode Tunable Filters Left Tunable Filters Right LR HR lowest freq you will hear highest freq you will hear bandwidth ZBP CW SSB Manual Notch The 2BP s bandwidth or selectivity is changed by adjusting the BP s bandwidth before selecting 2 BP Operation Error Main Document Only 9 MFJ 784B Instruction Manual Manual Notch Button When pressed in this button activates two manually adjustable notch filters Each filter removes a very
57. rt Open End Cables With Radio Connectors Open End Cable MFJ Part for Kenwood hand helds MFJ 5226 9 95 With 8 pin modular mic plug for Yaesu Kenwood MFJ 5268 9 95 Icom and Radio Shack Prices as of J une 30 1995 Prices subject to change without notice Appendix A 5 MFJ 784B Instruction Manual PreSet and Memory Filters Settings Chart Copy this chart and use it to record your PreSet and memory filters settings Use the Talk function to get the frequency values for CF BW and or LR HR PreSet RTTY Mode Mark Space Baud Rate PreSet AMTOR Mode MarkSpace Baud Rate Memory 1 Mode Operation Conditions Radio Frequency Pre Set HF PACKET Mode Mark Space Baud Rate Pre Set PACTOR Mode MarkSpace Baud Rate Memory 2 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 3 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 4 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 5 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 6 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 7 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 8 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 9 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 10 Mode Opera
58. t the notch frequencies you must select and adjust the correct main filter before using the manual notch The MF 784B always remembers the Tunable Filters left and right knobs settings when the manual notch is engaged and then the Tunable Filters left and right knobs will only adjust the two manual notch frequencies Another important thing to remember is when you release the Manual Notch button the main filter will still remain exactly as it was set The only thing that will happen is the notch will turn off But if you adjust or move either Tunable Filters left or right knob the main filter will quickly jump to the current control settings If you don t want to loose your original filter settings don t touch the Tunable Filters left or right knobs after using the manual notch You can adjust and use the notch as much as you like without affecting the original filter settings whenever the M anual Notch button is in Operation Error Main Document Only 10 MFJ 784B Instruction M anual Auto Notch Button The auto notch does nearly the same job as the manual notch except it finds and removes up to four unwanted tones very effectively The main advantage of the auto notch is that it hunts down and removes steady tones without any help from you The auto notch operates only in the LR HR BP 2BP and SSB filters regardless of whether they are saved in memory or not With the Auto Notch button in the MFJ 784B searches for heterodyn
59. ter on or off The Noise Reduction button operates in every filter mode including the memory positions Volume Control The Volume control adjusts the audio level at the Headphones Out and the Speaker Out jacks This control s position cannot be stored in memory and it operates all the time The volume control does not adjust the line level audio output at the Filtered Audio Out and To TNC output ports The Filtered Audio Out and To TNC output ports have a back panel screwdriver adjustment See the block diagram on page Error Bookmark not defined 4 Speaker Button This button turns the external speaker on or off It operates in any position of the Memory button and in every mode as long as the Power button is on Operation Error Main Document Only 12 MFJ 784B Instruction M anual DSP Button While in this button causes the DSP to digitally process the signal While out this button prevents the DSP from doing any digital processing It operates in any position of the M emory button Non processed audio is still available at all the audio outputs when this button is in the out position The only change is the audio output voltage at all the jacks including the Filtered Audio Out jack is no longer held constant The Volume control still functions with the headphones and speaker while the DSP button is out Power Button This button controls the power to the DSP It operates in any position of the Memory button When the
60. the unit s cover 6 screws Set the jumpers according to the jumper setting table on the next page Replace the unit s cover 6 screws Reconnect the power cable and resume normal operation NND Advanced Features Error Main Document Only 8 MFJ 784B Instruction M anual Normal J umper Settings Chart Tone Frequency H O wJ o oj un AW oj ojlojojojojoJjo o0 jojojojojojojo I I lI I Il l l l NININININ INI IN N Code Auto Notch Level ced Factory defaults This is what the jumpers should look 1000 Hz H H like for the following settings Tone Freq H 10 L 1000 Hz Talk pitch WPM H 10 WPM Talk Morse code speed ALS S and Auto Notch level 1 JMPB is NOT used Ad This is what the jumpers should look like ub dd d for the default settings NES 700 Hz Talk pitch level LJ 5 WPM Talk Morse code speed Auto Notch Lj and Auto Notch level 1 JMF is NOT used J Advanced Features Error Main Document Only 9 MF 784B Instruction Manual Setting the CW Sidetone Filter If you do not have a T R connection and wish to pass CW sidetone through the DSP you must enable this filter This is not the preferred method to pass sidetone see page 2 5 The CW sidetone filter is a jumper programmable internal constant frequency filter It only works in the Tunable CW mode Any signal within 30 Hz of the sidetone frequency will pass through this filter To enable the CW sidetone filter pr
61. tion Conditions Radio Frequency CF BW LR HR Appendix A 6 CF BW LR HR MF 784B Instruction M anual Pre Set and Memory Filters Settings Chart Copy this chart and use it to record your PreSet and memory filters settings Use the Talk function to get the frequency values for CF BW and or LR HR Pre Set RTTY Mode MarkSpace Baud Rate PreSet AMTOR Mode MarkSpace Baud Rate Memory 1 Mode Operation Conditions Radio Frequency Pre Set HF PACKET Mode Mark Space Baud Rate Pre Set PACTOR Mode MarkSpace Baud Rate Memory 2 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 3 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 4 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 5 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 6 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 7 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 8 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 9 Mode Operation Conditions Radio Frequency CF BW LR HR Memory 10 Mode Operation Conditions Radio Frequency CF BW LR HR CF BW LR HR Appendix A 7 MFJ 784B Instruction Manual PreSet and Memory Filters Settings Chart Copy this chart
62. to the frequency range of 0 3900 Hz or 175 Hz minimum in SSB mode When a filter s center frequency setting is low or high enough that the bandwidth would exceed these frequency ranges the filter is limited The filter actually changes its center frequency and bandwidth settings so that it does not exceed these frequency ranges Limited filters are probably not even noticed by the casual operator However when using the Talk feature an operator may notice a difference in the front panel controls and the Tunable Filters left and right knob settings Limited filters can only occur in the following filter modes LR HR BP 2BP CW and SSB For example The Filters switch is set to BP The Tunable Filters left knob is set at a 300 Hz center frequency and the Tunable Filters right knob is set to a bandwidth of 2000 Hz Obviously the lower cutoff frequency cannot be 700 Hz Since the DSP s frequency range stops at zero the filter must stop at zero The filter s upper cutoff frequency is 1000 Hz above the center frequency 1300 Hz In this case the DSP limits the BP filter to 0 1300 Hz a lowpass filter Therefore when the Talk feature is used the DSP will send the following BP CF 650 BW 1300 Filter Description 5 11 MF 784B Instruction Manual Overlapped Filters When the passbands of two filters touch each other the filters are said to be overlapped The result is a single band pass filter capable of passing all the frequencies
63. ture also allows you to measure a frequency from 300 Hzto 1000 Hz The Talk routine uses the following abbreviations CF Center Arequency BW BandWidth L Notch Frequency 1 Tunable Filters Left Knob R Notch Frequency 2 Tunable Filters Right Knob MN Manual Notch AN Automatic Notch NR Noise Reduction Talk will send the following settings for a selected Normal or Memory filter filter mode LR HR BP 2BP CW SSB RTTY etc lower and upper cutoff frequencies or center frequency and bandwidth state of the manual notch and its two notch frequencies state of the auto notch and its aggressiveness level setting 1 4 and state of the noise reduction filter and its front pane level 1 10 The Talk tone frequency and Morse code speed are jumper programmable Factory default speed is 5 words per minute WPM with a 700 Hz pitch See J umper Settings on page 4 8 Talk Operation To activate the Talk function Select a filter using the Filters switch and the Memory button Set Volume to comfortable listening level Disengage the DSP button to out Press and release the Program button Listen to the unit send the filter settings see examples on the next page At anytime press and lock the DSP button to stop the message ec ER Advanced Features Error Main Document Only 5 MFJ 784B Instruction Manual Examples This is an hypothetical example Suppose you forget what is stored in memory filter 3 To fin

MFJ-784B Manual Rev. 1C

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