Complete Kit Instructions (440 PDF)
Contents
1. LM324 quad op amp ECG987 SK3643 Radio Shack 276 1711 etc 1 each 14 pin DIP IC socket Radio Shack 276 1999 Highly recommended 1 each Dynamic Speech Processor PC board 1 piece each RED and BLACK 22 AWG stranded or solid hookup wire Radio Shack 278 1218 278 1224 1 piece RG 174 U or similar shielded audio cable Radio Shack 278 512 Alpha 2254 1 Mouser 178 1803M etc A complete kit is available for 38 including shipping from CBC INTERNATIONAL P O BOX 30655 TUCSON AZ 85751 USA TEL amp FAX 1 888 I FIX CBs 1 888 434 9227 Local 520 298 7980 Internet www cbcintl com Email info cbcintl com DYNAMIC SPEECH PROCESSOR PAGE 6 dn Aem y je poun pajA pue GuIpsiym pno jaaaj andu AWOOZ _ yi oiwEeUAp puepueys Buisn sjenoj yeod yeod ayewixoiddy L OCA 02 9 abeyjoA Jouez ey 0 Jenbe Ajayewnxoidde suid sayjo y SGA 00 LI Uld OCA SL EL p Uld Ol PZEWT VWEZOJAGA GL EL 2A SAOVLIOA LSAL 3A 1eAleosuey eje s pijos pue y o WeUAp souepaduil Mo prepueys Joj poreduin umoys sejqeo LNdLNO PWE LNANI S 7xaj aeg peyddns jou Buyayyy jeuogdo ase 749 149 Y s d oq 104 papiaoid sajoy osip arlzz o 10 grip o 10 onAjonooya arip 10 4rizp o aq kew g3 e Ajijenb eo10A jesnjeu sou 104 Ano pue gripoo uaamgaq uasoys po z pejou esimueypo ssejun M y ere sI0 siSel IV T SILON lt yju 7 4B1y 9 a9 9 10 yzy qns ano olpny MOU ZYA P2. R3 220Q red red brown VRI VRI 10KQ trimpot 10 mm horizontal R4 1KQ brown black red mounting Mouser 32AA401 CONSTRUCTION NOTES 1 Observe diode polarities Install D1 D2 and D3 with banded ends as shown 2 Observe electrolytic capacitor polarities C2 C3 C5 C6 C9 will normally have the end marked on the capacitor body and the PCB has the end marked 3 Use cut off lead wires for the jumpers J between the Z L or H holes See text install in appropriate holes for type of mike to be used 4 Electrolytics may be either the axial lead or radial lead type holes are provided for both Radials are shown with dotted circle C6 may also be a disc capacitor 5 Parts values aren t critical except C7 R13 C8 R14 for filter Substitute next standard value up or down if you can t find exact parts DYNAMIC SPEECH PROCESSOR PAGE 8 HOW TO FIGURE THE VALUE OF RESISTORS 8 CAPACITORS These parts use the Electronics Industry Association EIA standard marking Resistors have always had a simple color code but nowadays many disc and mica capacitors use EIA markings Especially true when dealing with Japanese parts The information here should make it very easy to figure the values of these parts Remember many capacitors will have the values marked directly in micro farads uF or picofarads pF After a while you will easily see from the physical size of the capacitor what the ap
3. set VR2 for 100 modulation then use a stock mike with the DSP to conveniently control the clipping level Good DX ing If you need help finding the right audio ground or DC power connections in your rig we ll try to help Send a 10 business size self addressed stamped envelope and the exact manufacturer s make or model of radio to CBC INTERNATIONAL P O BOX 30655 TUCSON AZ 85751 U S A DYNAMIC SPEECH PROCESSOR PAGE 14 IMPORTANT INSTALLATION NOTICE In many installations squeal will occur unless certain modifications are made The squeal is caused by either RF feedback or excess audio gain and is specific to certain radios The most common models having this problem include all Uniden and Uniden clone SSB models such as Cobra 140GTL 142GTL 148GTL 2000GTL 2010GTL Uniden GRANT GRANT XL MADISON WASHINGTON Uniden uPD2824 SSB types and dl Uniden clone export models like Galaxy etc There may be other brands and models as well You must decouple the excess RF if this is the problem If the following steps don t eliminate the squeal then try the methods described below under EXCESS AUDIO GAIN RF DECOUPLING Install a ceramic disc capacitor 470 pF to 001 uF directly across the mike audio and ground chassis common not metal case right at the inside of the mike socket itself keeping the leads very short A 001 uF capacitor is included in our kit In addition you may need another on
4. BLACK CF AC PLUG Ac A De REGULATOR TRANSISTOR DC INPUT PC BOARD NOTE Additional PCB holes are provided for two types of filter capacitors if needed These are labeled CF1 and CF2 on the X Ray View and Circuit Diagram Occasionally the use of a linear amplifier high antenna SWR or poor radio filtering will cause RF feedback or squealing during TX Sometimes an AC hum will appear on the transmitted signal due to poor AC filtering in a base radio A 01 uF or 1 uF ceramic disc at CF1 may help the RF feedback problem and an electrolytic capacitor of 10 100 uF at CF 2 should cure the AC hum problem Holes are provided to fit many types of capacitors This problem is rare and generally only happens if you put the DSP in an external plastic box with long power wire leads from the rig or from a separate DC supply Before adding such capacitors read the special notes on Page 16 first most problems will be cured using those tips instead Many people have asked about installation in a separate box external to the radio with an IN OUT switch for those occasions when speech processing isn t needed Shown next is the basic hookup You would need to install suitable mike plugs and sockets on a metal mini box or run a bunch of loose wires to the radio On base rigs it s best to use 9 volt battery power instead of the main AC to minimize hum or RF pickup You ll need a 3PDT switch to kill the battery power in the OUT
5. The end is marked on the PCB for easy identification 3 Save some of the cut off parts leads to use for the Z L or H jumper holes as described in the THEORY and INSTALLATION sections 4 Observe polarity of electrolytic capacitors The ends are marked on the PCB and usually the ends are marked on the plastic vinyl covering the capacitor body The lead is usually longer too 5 If you re building from our plans using your own parts you ll see a few extra PC foil pads and holes These are provided so the most common electronic parts sizes will fit in the PC hole spacings 6 Recheck all work for shorts solder bridges and proper parts locations Check proper polarities of diodes and electrolytics Holding the PCB up to a strong back light will easily show any possible shorts Clean off the solder flux with acetone or flux remover Radio Shack 64 4330 etc for a professional finish to your kit This also makes it much easier to spot bad solder joints or bridges If you expect your kit to work properly try very hard to install the parts neatly and correctly as shown in the X Ray View and the photograph Press all parts down tight against the PC board rock the diode or resistor leads back and forth while pressing until they fit flush against the PC board DYNAMIC SPEECH PROCESSOR PAGE 4 Polyester Ceramic A Locating IC pin 1 2N3904 small indent Notch Dot r Eg PIN1 PIN P
6. 01 uF disc capacitor placed directly across the center and shield of the GRAY INPUT cable at the mike socket should stop it Sometimes a second 001 uF capacitor is needed inside the mike itself Don t get carried away though or you may start losing the higher audio frequencies Also keep the BLACK power wire as short as possible and solder it directly to the nearest metal transformer In really tough cases add one or more RF chokes of about 470 uH in series with the INPUT and or OUTPUT leads to decouple all the stray RF See Page 16 for details When your only test instrument is a DC voltmeter you can still get a rough test for clipping action by placing the lead at the junction of R10 D1 D2 It normally reads 0 9 VDC here with VR1 at maximum a loud whistle into the mike will deflect the voltage downwards Power mikes are really not needed not recommended and often complicate the installation The D104 types are the worst We can t guarantee they ll work If you insist on trying be sure to move the input jumpers from the Z and L holes to the Z and H holes This adds a 10 1 voltage reduction to prevent the power mike from overdriving the DSP The power mike s control will then make a convenient clipping adjustment control By setting VRI for maximum you can use the mike s control to change the clipping as desired If your radio has a MIKE GAIN control this makes an even better method Set that and VRI to maximum
7. CONSTRUCTION INSTALLATION 8 OPERATION DYNAMIC SPEECH PROCESSOR Have you ever wondered why every AM or FM Rock broadcast station always sounds so loud or why the sound portion of TV commercials always seems louder than the program itself The reason is that smart broadcasters use exactly the same powerful principles of audio processing that are now available to you with the Dynamic Speech Processor DSP The nature of the human voice is such that it normally modulates a radio transmitter only about 30 on the average Almost all the intelligibility or readability of the voice is contained in the consonant sounds such as B K S etc However these sounds contain very little average power On the other hand the vowel sounds A E I O U don t add greatly to readability but do contain high intensity spikes or peaks that can easily overmodulate a transmitter Therefore if we can increase the energy of the consonant sounds relative to those of the vowel sounds the average audio power will be noticeably increased The signal will come across with more punch or talk power With correct speech processing it s possible to increase the average modulation to about 90 At the same time the voice frequencies under 500 Hz and above 2500 3000 Hz don t add much readability or average power and aren t needed for voice communications typical of two way radio What s needed is a circuit that will cut off or clip the
8. F or 0 01 uF e none 472K 47 x 100 4700 pF or 0 0047 uF 10 202 20x 100 2000 pF or 0 002 uF color band means temp coefficient N significant figures Oo g 10 000 tolerance A in critical circuits multiplier decimal point NOTE L ko Aaa e ka 2nd digit Ein w amp multiplier 21k J 5 K 10 M 20 1st digit p Pico Farads TT n Nano Farads Mica capacitors are generally 5 and use the same code so 270J 27 x 1 27 pF 5 and 271J 27 x 10 270 pF 5 etc Capacitors with no tolerance letter are read directly 360 360 pF DYNAMIC SPEECH PROCESSOR PAGE 9 INSTALLATION The DSP connects in series with the mike and the main audio input circuit of the radio Operating power comes directly from the radio The DSP is meant to fit inside the radio permanently however instructions for external box mounting are shown later With box mounting it would be best to power the unit directly from a 9 volt battery Two PCB mounting holes are provided for bolting the PCB using 6 32 or 4 40 nuts and bolts If washers are used be very careful that they don t short out to any PCB foil traces If you don t want to bolt it in the unit can simply be laid inside the radio s cabinet after adjustment with the solder side up to prevent shorts Avoid mounting in the area of the RF power circuit This area is near the antenna coax socket at the rear or along one side of the frame The DSP is soldered to the ins
9. IN 1 c apply heat to side place solder of lead and foil good shiny N opposite iron amp smooth S SOLDERING CIRCUIT SPECIALISTS INC 220 S Country Club Dr 2 Mesa AZ 85210 TEL 800 528 1417 480 464 2485 FAX 480 464 5824 www cir com or www web tronics com DIGIKEY CORP 701 Brooks Av South P O Box 677 Thief River Falls MN 56701 TEL 800 344 4539 218 681 6674 FAX 218 681 3380 www digikey com Mica n CAPACITORS Radial Electrolytic Tantalum Axial Electrolytic Trimmer Q g Band is N DIODES er an Match band GG on PCB Xd End poor flaky y dull ragged A DA De use needle nose pliers to remove excess coating from leads before inserting in PCB PARTS SUPPLIERS MOUSER ELECTRONICS 1000 N Main St Mansfield TX 76063 TEL 800 346 6873 817 804 3888 www mouser com ALLIED ELECTRONICS over 80 locations all over the U S Main HQ 7410 Pebble Dr Fort Worth TX 76118 TEL 800 433 5700 817 336 5401 FAX 817 595 6444 www avnetallied com DYNAMIC SPEECH PROCESSOR PAGE 5 DYNAMIC SPEECH PROCESSOR PARTS LIST Parts are designated by their locations on the X Ray View and Schematic Resistors VRI VR2 10KQ Mouser 32AA401 32RH401 32RW401 DigiKey K4A14 Circuit Specialists 32AA401 32JR401 etc These are miniature 0 1 watt horizontal mounting 8 or 10 mm 8 10mm CARBON or CERMET TRIMPOTS 1 each 330Q 2 watt 5 carbon oran
10. SPEECH PROCESSOR PAGE 10 On these rigs you can also locate the mike audio terminal by either shorting the pair that keys the Transmitter or use the radio s mike to key the Transmitter Then touch each of the other terminals with your finger while listening to the carrier on another CB tuned to the same channel When you touch the mike audio line with your finger you should hear a carrier hum on the other radio A few rigs use remote controls Squelch Volume Channel Select built into the mike and may require the actual circuit diagram to find the specific connections Shown below are the mike plug numbers for the most common CB socket types O OF 10 sO 20 O M F 4 PIN FEMALE 5 PIN FEMALE 5 PIN DIN 6 PIN DIN WITH COUPLING NUT WITH COUPLING NUT When you ve located the mike audio and ground pins unsolder the audio wire from its pin Connect this wire instead to the center conductor of the GRAY shielded cable on the OUTPUT side of the DSP The OUTPUT cable is the one coming from the PCB holes marked G 1 or 2 The shield at the loose cable end isn t needed and can be cut off or taped back against the vinyl covering Now connect the loose cable end of the DSP s INPUT side to the mike audio and ground pins on the mike socket The INPUT cable is the one connecting to the G and the IN holes on the PC board Connect the center conductor of the GRAY cable to the now empty socket pin and the shield to
11. STATE DESIGN FOR THE RADIO AMATEUR ARRL address above LINEAR IC DATA BOOK National Semiconductor Inc 2900 Semiconductor Dr P O Box 58090 Santa Clara CA 95052 TEL 800 272 9959 408 721 5000 FAX 408 739 9803 ASSEMBLY INSTRUCTIONS PLEASE READ CAREFULLY BEFORE PROCEEDING NOTICE This device will operate as advertised when properly constructed installed and adjusted CBC INTERNATIONAL has no control over the skill of the builder therefore no warranty can be given We will accept for repair units built only from our own kits for 25 prepaid with returned unit NO BASKET CASES PLEASE Proper soldering is essential and poor solder joints are the single biggest cause of problems Finished joints should look shiny never dull Use only a small iron 25 45 watt with a very fine round or slot tip to avoid shorts See the sketch at the top of the next page for soldering tips Assembly consists of stuffing the parts into the proper PC board holes as illustrated in the X Ray View drawing Page 8 Check against the Schematic if you re in doubt about the correct holes Push all parts down tight wiggling back and forth if necessary as you press down See photo Page 15 The diodes and resistors will bend naturally to the proper hole spacing NOTES 1 Pin 1 of the LM324 is clearly marked by a tab on the PCB See sketch on next page 2 Diodes must be installed with the banded end in the correct hole as shown in the X Ray View
12. a Indino m yovid MY Az 9 kepi arizz i wade anor u ojpny L loan s ers snq 30A 7 9 a dex i MI MO La vu l ka sa A09 7 ri azy A AU OOP OL ly r 0 l mi FHA y u Z YBIY a 7 L ONIddI19 ai iy 10 JZP ans anzy zz y YL6NL PL6NE jdzy MiP mon 2 AL 441 92 za La 9 a d a ie HY H LAS sa n WI 70 Z SY MOU m sa r 5 M MI 7 cr weibeig yna onewsayos gTa bT PAGE 7 DYNAMIC SPEECH PROCESSOR X RAY VIEW TOP PARTS SIDE z CLIPPING C1 01 uF ceramic disc R5 10KQ brown black orange C2 4 7 uF 25 VDC electrolytic R6 47KQ yellow violet orange C3 4 7 uF 25 VDC electrolytic R7 1KQ brown black red C4 002 uF ceramic disc R8 IMQ brown black green C5 4 7 uF 25 VDC electrolytic R9 1KQ brown black red C6 1 uF or 0 47 uF 25 VDC electrolytic R10 10KQ brown black orange or 0 1uF 0O0 22 uF ceramic disc R11 1KQ brown black red C7 002 uF ceramic disc C8 150 pF ceramic disc C9 4 7 uF 25 VDC electrolytic CFI CF2 See text Page 3 R12 100KQ brown black yellow R13 180KQ brown gray yellow R14 470KQ yellow violet yellow D1 D2 1N914 fast switching silicon RIS E eae D3 IN4735A 6 2 volt e watt Zener RIO TOK pron baek orange IC1 LM324 quad op amp R17 10KQ brown black orange R1 330Q watt orange orange brown RL1 RL2 RHI 1KQ brown black red R2 1KQ brown black red RH2 100Q brown black brown
13. e soldered directly across the DSP foil traces where the INPUT gray cable enters the PC board Don t use any capacitor larger than about 001 uF or you may lose some of the higher audio frequencies Also solder the BLACK DC power wire to the shortest most direct chassis common point possible Usually this will be at one of the metal tuning transformer cans on the radio PC board Solder will stick to these cans NOTE Do not run the BLACK power wire back to the rear DC input point Besides the long wire length the DC input socket is RF isolated from chassis common by a small choke in most radios and could create a ground loop that makes the problem even worse Ground the BLACK wire only to the same common point as the audio ground metal transformer cans etc In the Uniden MB8719 type PLL radios it may help to power the RED lead from Pin 1 of the MB3756 voltage regulator IC 8 VDC which provides somewhat isolation and filtering than the 13 8 VDC bus For really stubborn cases you may need to add an RF choke of about 470 uH in series with either the INPUT or OUTPUT or both center conductors of the GRAY cables Some rigs like the Uniden HR2510 will definitely need this modification Put the RFC directly on the main PC board where the audio signal enters from the mike socket PC board We stock these chokes in a 5 pack only 6 00 postpaid EXCESS AUDIO GAIN This is an equally common problem caused by the high gain of the DSP in ser
14. eak into the mike in a normal voice or whistle while turning the CLIPPING OUTPUT trimmer VR2 for 100 modulation Then turn up the INPUT trimmer VRI until the voice sounds strong and punchy without being too fuzzy harsh or distorted The voice may sound slightly less natural but otherwise quite clear Don t advance either trimmer up too far or you may get self oscillation squealing due to the overall high gain of the combined DSP power mike if used and radio circuits all working together The majority of newer rigs have very high audio gain and may oscillate with over adjustment The DSP is designed to provide approximately the same peak peak audio output about 3 0 V as the output from a typical dynamic mike preamp If you can t lower the OUTPUT far enough to prevent overmodulation move the center conductor of the OUTPUT cable over to the 2 hole This puts another 10KQ series resistance in line through R17 to reduce the OUTPUT level If the radio s modulation limiting circuit AMC or control pot was turned up or removed it should be restored to normal Without it you will severely overmodulate and cause lots of channel bleedover Those modifications aren t needed at all with a properly adjusted DSP Remember the whole idea is to maintain near 100 modulation but no more The squeal problem is very common in many newer Uniden SSB rigs such as the Cobra 140 142GTL Cobra 148 2000GTL and any uPD2824 SSB type chassis A 0
15. er exceptions are the Uniden uPD2824 SSB chassis Cobra 146GTL President AR 144 etc and export rigs such as the Cobra 148GTL DX The majority of CBs use either the 5 pin DIN socket a 6 pin DIN or 4 pin or 5 pin male socket with threaded coupling nut Unless you have the radio s schematic diagram you must figure out which wire performs which function To do this use a piece of wire or a clip lead touching it to pairs of socket terminals and observing what happens You should find the following 1 One pair will key the transmitter GROUND plus TX 2 One pair will cause the speaker to be heard GROUND plus RX 3 The fourth wire is the mike audio line you are looking for The one wire that was common to all the other functions is the ground terminal If you have an ohmmeter check each terminal by connecting one ohmmeter lead to the black power connection of the radio and the other lead to each socket pin The one socket connection that shows zero ohms is the ground or common terminal Once you know the ground terminal you can connect across it and the other terminals one by one You ll find that one terminal keys the Transmitter and one causes the speaker to be heard If the socket only has four terminals the remaining terminal logically must be the mike s audio terminal If the radio uses a 5 or 6 pin socket there may be more than one ground because only four wires are needed for electronic T R switching DYNAMIC
16. ge orange brown The following are all 14 watt 5 carbon types 1 each 100Q brown black brown 1 each 220Q red red brown 9 each 1KQ brown black red 4 each 10KQ brown black orange 1 each 47K yellow violet orange 1 each 100KQ brown black yellow 1 each 180KQ brown gray yellow 2 each 470KQ yellow violet yellow 1 each 1MQ brown black green LA Capacitors RADIAL NOTE You can substitute Tantalums for the AXIAL ELECTROLYTIC electrolytics at slightly higher cost ELECTROLYTIC 1 each 150 pF ceramic disc 2 each 002 uF ceramic disc 1 each 01 uF ceramic disc Radio Shack 272 131 These are all low voltage 25 50 VDC types which are physically small enough to fit across the PCB hole spacings CERAMIC DISC CAPACITOR DIODES 4 each 4 7 uF 25 VDC electrolytic Radial or axial lead types Radio Shack 272 1012 axial 272 1024 radial 1 each 1 uF 25 VDC electrolytic or tantalum Radial or axial lead type Radio Shack 272 1434 NOTE For 1 uF electrolytic you can sub 0 47 uF electrolytic 0 47uF ceramic Radio Shack RSU11298320 0 1 uF electrolytic or metal film Radio Shack 276 1069 276 1053 0 22 uF ceramic or electrolytic Radio Shack RSU11298312 272 1070 Diodes 2 each 1N914 or 1N4148 type fast switching silicon SK3016 ECG177 Radio Shack 276 1122 etc 1 each 6 2 volt 2 watt Zener 1N4735A 1N5234B Radio Shack 276 561 or RSU 11673498 ECG5013A SK3058 etc Miscellaneous 1 each
17. h a 47KQ resistor These changes for high impedance circuits will ensure the proper impedance matching Refer to the X Ray View and Circuit Diagram for parts locations DYNAMIC SPEECH PROCESSOR PAGE 11 BASIC PROCESSOR INSTALLATION IN SERIES WITH MIKE AUDIO LINE COKKEST TOGETHER SOU MER TAPE CEP TYRICAL MIKE SOCKET THREE an RK EFRR LWE CERTA FO HEE AG THELD TO ROU RI kai ORR AE GfIGN L WHE WIRE i E af GEA bE COMMON n MAY BE TAR ON FIM SACHETS NEWER RADIOS Colored wires on all the mike socket pins OLDER RADIOS Colored wires or small shielded cable on mike audio and ground All that s left is to connect the 12 volts DC from the radio All solid state transistor radios including base types have this voltage available It s closer to 13 8 VDC On tube type rigs there may be both low and high voltage sources or high voltage only But you can still connect the DSP s RED wire to a high voltage DC source by using a series dropping resistor to get the required 12 14 volts DC Since the DSP draws about 24 mA 0 024 Amp total current use Ohm s Law to calculate the required series resistor For example if a 250 VDC power source is available in the radio you want to drop 250 12 238 volts of that The series dropping resistor would be R E 1 R 250 12 0 024 Amp 9 916 ohms A standard 10KQ 1 or 2 watt resistor could be used CAUTION HIGH VOLTAGES ARE LETHAL If you have the slig
18. hese diodes D1 and D2 are forward biased slightly by R9 R10 and R11 to make the clipping start more quickly The resting DC voltage at their anodes is about 0 82 VDC which means any signal above this preset level is automatically clipped This ensures that at high modulation levels clipping action will be almost constant Since clipping produces undesirable harmonics that cause channel bleedover they re removed first by a low pass filter consisting of R12 and C7 They re further reduced along with unneeded voice frequencies above 3000 Hz by A4 A4 acts as both an amplifier and an active filter with R13 and C8 being the filter elements The processed signal is coupled through C9 to the output level adjustment VR2 Following VR2 are two output paths one directly from its wiper Hole 1 and one through R17 Hole 2 In most applications the output can be taken directly from Hole 1 In a few cases where it s impossible to control the transmit modulation level because the overall gain of the radio and processor together are too high Hole 2 can be used This puts another 10KQ in series with the output to lower the audio level reaching the transmitter In true high impedance input circuits you can replace R17 with a resistor of 47KQ 100KQ and use it with Hole 2 for impedance matching Most radios can use Hole 1 directly without changes Please read the special modification notes on Page 16 before you build the kit these apply to many popu
19. high intensity peaks increasing average modulation and at the same time reducing the strength of the unnecessary voice frequencies That s the purpose of the DSP Unlike all common CB power mikes the use of clipping is much more effective for radio communications Power mikes are either ordinary circuits that amplify all voice frequencies equally or they operate on the principle of audio compression Compression simply amplifies the weaker voice elements relative to the peaks These mikes are very sensitive to background noises and AC hum on base stations Many tests over the years have shown that compression isn t nearly as effective as clipping and its actual increase in readability is only about 1 dB Compare the two photographs below which clearly illustrate the advantages of clipping With the DSP there s a very noticeable difference in talk power Up to 15 dB of clipping is quite acceptable to the ear has little effect on voice quality and provides about 4 dB of true signal readability improvement This 4 dB is equal to BEFORE PROCESSING AFTER PROCESSING Actual photograph of a speech waveform This photograph shows a correctly processed without any processing as present at the mike speech waveform The average is much higher input of a transmitter Note the very high peak than before but the peaks are slightly lower amplitude compared to the average levols This is a considerable increase in the average power output but
20. htest doubt about installing the DSP in a high voltage tube type transceiver let a qualified technician do it On mobiles and bases connect the BLACK DSP power wire to any convenient ground or common point It may be marked on the chassis or power socket You can also find the common circuit foil by using an ohmmeter to check for continuity between the intended connection point and the ground you already know on the mike socket Now connect the DSP RED wire to the radio s main DC power located at the ON OFF VOLUME control This is usually RED or ORANGE Connect to the switched side not the input side On solid state mobiles this is always the proper point However a few old base transceivers switch the AC mains at the ON OFF VOLUME control connection there will instantly blow out the DSP Those base rigs are extremely rare now but if in doubt you should test the connection point with a voltmeter first You can also find the 13 8 VDC on the converter PC board used in base type rigs This is a small PC board close to the large power transformer on the chassis The DC is typically available at the Emitter of the large PNP series regulator transistor on this board The following shows base and mobile hookups Don t rely solely on the GRAY wire shield for the DC return path always use the BLACK wire DYNAMIC SPEECH PROCESSOR PAGE 12 BASE DC POWER SOURCE MOBILE DC POWER SOURCE DSP a ONIOFFVOL i SWITCH A RED and
21. ide of the mike socket where the audio line and ground are located If the radio doesn t use a socket you ll have to follow the mike cord into the main chassis and determine which wire is which Many newer models use ribbon cables to tie the front panel s PCB to the main PCB this may require a service manual or schematic to find the exact wire If you don t have a circuit diagram of the radio you can usually figure out which mike wire is which as explained next All transceivers use either relay or electronic T R switching Relays are more expensive so only the older 23 channel SSB rigs a few of the better old 23 channel AM rigs and some Ham rigs use relay switching All the rest use electronic switching You can decide which type you have in two easy ways 1 Look inside on the main radio PC board for the relay which is a large rectangular plastic object about 1 long If you see one key the mike and watch to see if the relay contacts move a few rigs contain extra relays that are used for other than T R purposes 2 Unplug the mike If you can still hear noise from the speaker you most likely have relay switching electronic switching disconnects one side of the speaker circuit on Transmit CAUTION A few rigs like some Realistics with the 5 pin DIN socket have special shorting terminals so that the speaker will still be heard even with the mike unplugged However these rigs are still electronically switched so be aware Some oth
22. ies with all the existing audio gain already in the radio First make sure you ve used the 2 OUTPUT hole which adds the 10KQ series resistance of R17 Next replace R12 100KQ brown black yellow with 470KQ yellow violet yellow which will sharply reduce the DSP s total gain An extra 470KQ resistor is included with our kit Refer to the X Ray View on Page 8 to locate R12 All the radio types listed on this page will need this minor parts change We suggest you do it while you re building the kit and avoid having to unsolder the 100K resistor at all DYNAMIC SPEECH PROCESSOR PAGE 16
23. lar models The processor is powered from the radio s main 13 8 VDC source D3 is a 6 2 volt Zener diode that provides a well regulated power source to the processor RF is decoupled from the DC power supply by Cl Holes are included on the circuit board for extra filter capacitors CF1 and CF2 dotted lines For RF filtering CF1 can be a Ol uF or 1 uF ceramic disc type CF2 would be a large electrolytic of 10uF 100 uF and would help reduce AC hum pickup if the DSP is powered by a poorly filtered radio or AC to DC converter These parts not included in kit A small disc capacitor of 001 uF can sometimes help reduce RF feedback squealing in certain situations you would install this directly across the gray INPUT cable s center and shield wires RF chokes of about 470 uH can also be used and would be wired in series with the INPUT or OUTPUT or both center conductors NOTE Linear amps are common among CBers now and most are very poorly designed They are guaranteed to cause feedback squeal and are not recommended when using the DSP DYNAMIC SPEECH PROCESSOR PAGE 3 REFERENCES 8 SUGGESTED READING RADIO HANDBOOK any recent edition by William I Orr MacMillan Publishing 11711 N College Av Carmel IN 46032 TEL 800 428 5331 317 573 2500 THE RADIO AMATEUR S HANDBOOK any recent edition by American Radio Relay League ARRL 225 Main St Newington CT 06111 TEL 800 243 7767 203 666 1541 FAX 203 665 1166 SOLID
24. ount of input clipping are fully adjustable using small trimmers This means your mike audio is increased to a much higher average power level but without causing needless interference In other words LOUD Over the years our Dynamic Speech Processor kit has undergone many changes to make it even more effective and easier to build Our current design uses the very reliable LM324 op amp and can be installed in just about any combination of radio and mike equipment Two user options when building the kit make the DSP easily compatible with both high and low impedance mikes and most power mikes We ve included special holes in the PC board for those rare times when extra RF or AC filtering may be needed These options are fully explained below and in the INSTALLATION section THEORY OF OPERATION Refer to the Schematic Circuit Diagram Page 7 The incoming mike signal is first coupled through C2 to an input matching and gain level buffer circuit at Al A1 is one of four sections of an LM324 quad op amp IC The user can select several possible options here to make the DSP compatible with most low impedance dynamic mikes power mikes or high impedance mikes This is done by choosing among jumper wire combinations when building the circuit The gain of an op amp is set mainly by the ratio of input resistance to feedback resistance Therefore separate pairs of resistors with different gain ratios are used at RL 1 RL 2 RH 1 and RH 2 The impedance seen b
25. position any time the DSP isn t in use CAT Se grt 45 12 VDC FROM av BATIERYOR RIG m NOTE Although we are including information for an external hookup this isn t recommended due to the problem of RF feedback in long wires Install it this way at your own risk A much better idea if your rig has a MIKE GAIN control is to use that to control clipping levels Install the DSP internally and set it to maximum clipping Then adjust the MIKE GAIN as needed ADJUSTMENT 8 OPERATION Normally an oscilloscope should be used for proper adjustment of any speech processor Since this is a very expensive instrument and usually only available to technicians an inexpensive Modulation Power SWR type meter or the rig s own if present can be used instead The basic idea is to set the INPUT clipping pot VR1 for the desired amount of clipping while adjusting the VR2 OUTPUT pot for 100 modulation of the transmitter Both adjustments will interact slightly so that if clipping is turned down the output may have to be turned up and vice versa Since most operators install the DSP permanently inside the transceiver this should be a one time set it and forget it operation DYNAMIC SPEECH PROCESSOR PAGE 13 Have a friend listen to your transmitted signal or else use a second radio tuned to the same channel Begin with VRI and VR2 trimmers at their midpoint The following sketch shows the direction of maximum levels for both adjustments Sp
26. proximate value should be For example a disc marked 005 means 005 uF while a disc marked 68 means 68 pF A 0 1 uF disc is always physically larger than a 01 uF disc of the same voltage rating and so on Mo 4th BAND TOLERANCE CBC KITS ARE 5 COLOR 1st DIGIT 2nd DIGIT MULTIPLY BY Typical carbon composition resistors like those used in most kits have four color bands The first three colors represent the first digit second digit and decimal Brown multiplier in that order The fourth band is the tolerance 2 n ea 100 value Our kits use 5 types This means that a 1KQ 5 3 1000 resistor can measure between 950Q and 1050Q The Yellow 4 4 10 000 same tolerances apply to capacitors The tolerance band is always silver or gold so it s easy to know which end to Green 2 2 000 000 start counting from Violet 7 7 10 000 000 EXAMPLES Gray 8 8 100 000 000 White 9 9 1 000 000 000 YELLOW YELLOW RED sou RED GOLD NOTE K 1 000 KILO M 1 000 000 MEGA Thus 10K 10 000 GOLD SILVER Q 10M 10 000 00002 Begin with the GOLD or SILVER band on your right Then read from left to right to get the first digit second digit and decimal multiplier SILVER 4th band 10 GOLD 4th band 5 no 4th band 20 aero ATO ST IO DISC CAPACITORS in pF pie ea pak en x p gt O IF 3rd CAPACITOR MULTIPLY ki l NUMBER IS BY a en 10x1 000 10 000 p
27. the ground terminal right along with whatever radio wire is already on that pin As shown on the next page you have simply installed the Processor s audio INPUT and OUTPUT cables in series with the radio s mike audio line NOTES 1 Many newer radios Cobra 140 142GTL etc connect a separate small PC board to the mike socket pins This board has all the same functions TX RX AUDIO GROUND Locate and unsolder the audio wire and tack solder the GRAY cable on to the small mike PC board instead 2 A few old relay type CBs and HAM rigs use a small shielded wire running to the mike socket which carries the audio signal If you have this type you can unsolder both center wire and shield and connect to center and shield of the GRAY DSP output cable this provides better audio shielding 3 Make sure you have installed the jumper wires as described in the THEORY and the ASSEMBLY sections to the correct holes that match the type of mike you are using To repeat both jumper wires should connect between the Z and L holes for stock low impedance mikes and between the Z and H holes for power mikes If yours happens to be an old tube type rig or the mike is crystal or ceramic these are high impedance circuits In such cases remove resistors RH 1 and RH 2 and replace both with 47KQ resistors Not provided In addition the center wire of the GRAY output cable is moved over to the 2 output hole and R17 1OKQ is replaced wit
28. uction of about 10 1 since RH 1 1KQ and RH 2 100Q This makes a power mike much more compatible with the DSP If you have a true high impedance mike like the original non amplified D 104 or an older tube type radio replace RH 1 and RH 2 with 47KQ 100KQ resistors This makes a good impedance match with a zero gain buffered input at Al Continuing along the signal couples through C3 VRI and R3 to A2 the preamplifier VRI is the Clipping Level adjustment Clipping quires that a signal first be greatly amplified in voltage The combination of R5 and VRI R3 sets the gain of A2 which at its minimum setting has a gain of approximately 1 10K Q 10KQ 2209 and can be increased to about 45 10KQ 220Q The output signal couples through C4 to A3 the next amplifier stage The value of C4 is chosen for the most natural sounding voice quality and can be any ceramic disc capacitor from 001 uF to 1 uF The 002 uF value was chosen by experimentation As the value becomes larger closer to 1 uF the voice sounds more bassy and muddy The smaller value gives a good crisp voice quality because it can pass more of the higher voice frequencies The combination of R6 and C4 forms a high pass filter to reduce voice frequencies below about 500 Hz The output of A3 is coupled through C5 to the clipper circuit Two 1N914 fast switching silicon diodes are wired back to back such that one clips on negative modulation peaks and one on positive peaks T
29. without the risk of distortion Copyright 1979 2001 by L M Franklin All rights reserved CBC INTERNATIONAL P O BOX 30655 TUCSON AZ 85751 U S A TEL FAX 888 434 9227 520 298 7980 Email info cbcintl com more than doubling the effective transmitter power A 4 watt CB sounds more like 10 watts Further clipping up to about 25 dB is tolerable under conditions of heavy interference QRM It adds another 1 5 dB of readability to the signal but the distortion in the voice quality starts to become noticeable Another advantage of clipping is that background noise and hum aren t nearly as noticeable as they are in typical audio compression mikes That s because the DSP doesn t amplify the weak sounds relative to the strong sounds Instead it reduces the stronger low readability peaks relative to the weak ones The difference is very subtle but the results often mean a dramatic increase in real talk power The main problem with clipping is that it creates harmonics that can cause bleedover to adjacent channels Proper harmonic filtering is essential and must never be ignored In the DSP this filtering is easily done by adding a few extra parts at its output to form a Low Pass filter just like those used to reduce TVI Even a properly filtered clipping circuit can still overmodulate more than 100 and cause bleedover Any clipper circuit must also have some way to control its output level In the DSP both the output level and the am
30. y the mike itself is generally whatever the amp s input resistance happens to be and the jumper wires that connect between the Z holes and the L or the H holes can control this The Schematic shows jumpers set for a standard low impedance dynamic type mike The majority of modern CB and Ham rigs use low impedance mikes typically 300Q 1KQ Jumpering the Z to L holes puts resistors RL 1 and RL 2 in the circuit These are 1KQ each which will provide a good impedance match for this type of mike Since radio operators now tend to use either power mikes or stock low impedance mikes rather than high impedance mikes the RH 1 and RH 2 resistor values were chosen to match power mikes Power mikes use amplifiers having about 5KQ maximum output impedance depending on the setting of the mike control This is considered low impedance for our purposes A true high impedance mike has a crystal or ceramic element and is common in the older tube type CBs or high power Ham transceivers Those mike impedances are usually in the range of 47KQ 100KQ DYNAMIC SPEECH PROCESSOR PAGE 2 The problem with power mikes is that they tend to overdrive the input circuit of the DSP causing self oscillation and squealing Selecting the Z to H input jumpers reduces much of the power mike gain Since RL 1 and RL 2 are equal Al has no gain at all and acts only as a buffer By jumpering RH 1 and RH 2 in the circuit there s now a voltage red
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