Multicontroller User Manual
Contents
1. Multicontroller User Manual The W8ZR H F Receiver Multicontroller is an active 8 channel antenna distribution amplifier or multicoupler designed to cover the frequency range 0 1 MHz 55 MHz A low pass filter limits the high frequency response and an optional internal high pass filter can be installed to limit the low frequency response below 1 8 MHz The Multicontroller features a BNC input for 50 Ohm unbalanced coaxial fed antennas and an RCA type phono jack for high impedance antennas It has a front panel selectable low noise preamplifier and capability for muting any combination of seven receivers Grounding a control input mutes all seven receivers and internal protection circuitry disconnects the antenna and mutes all receivers if the external r f voltage exceeds 1000 mV There are seven BNC receiver outputs plus an auxiliary BNC output which is always active and can be used for an eighth receiver frequency counter oscilloscope etc The Multicontroller can also be used for testing production and frequency measuring and calibration It will transform almost any impedance to 50 Ohms can split a signal generator output into 8 isolated outputs It makes an excellent wideband buffer and line driver and provides a convenient way to control a linear amplifier I Front Panel Controls and Operation 1 Power Switch Connects AC power source to multicontroller through 1 4A fuse F1 1 8A for 230 VAC 2 Antenna Selector Sw2. enna Input high Z Impedance Clipping threshold Connector 6 Outputs each channel Impedance Connector 7 Preamplifier 12 dB nominal 8 Internal Noise V lt 02 uV V lt 30uV 50 Q load preamp off LF filter not installed 50 Q load preamp off LF filter installed 50 Q nominal d c blocked 1300 mV 18 dBm preamp off BNC 1000 Q nominal d c blocked 1500 mV preamp off RCA type phono 50 Q nominal d c blocked BNC 50 Q input only 1 kHZ bandwidth 10 MHz broadband 1 8 30 MHz 9 Absolute Maximum Input Voltage Maximum D C voltage 50 V Maximum RF voltage 3 5 V rms 10 Overload Trip Threshold 1000 mV rms nominal 50 Q and high Z inputs Mute and Control Circuits 11 Mute Specifications Independent mute outputs 7 Configuration open to mute or close to mute common ground Connector RCA type phono 12 Mute Relay Ratings max switched current 1 A derate as switched voltage increases max switched voltage 125 VDC 25 mA 150 VAC 100mA 13 Control Input ground to activate Open circuit voltage 12V Short circuit current 1 2 mA resistance to mute lt 2 2 kQ General Specifications 14 Power Requirements 90 130 VAC or 180 260VAC 15 Watts nominal fuse 1 4A 3AG 115V or 1 8A 3AG 230V 15 Dimensions Height 3 5 excluding feet Width 7 2 Depth 6 00 16 Weight 5 Ibs 2 27 kg
3. h having 50 Q output impedance These duplicate the signal that appears at either of the antenna input jacks Note that these outputs are active even when the connected receivers are muted but that they are inactive disconnected if the Overload LED is lighted 5 Aux Out BNC jack This buffered output is similar to the RX1 RX7 ports except that it remains active even if the Overload LED is lighted This output may be slightly more susceptible to strong signal intermodulation distortion than the other outputs because back to back protective diodes are connected to the input of the Aux Out amplifier stage 6 RX1 RX7 Phono Jacks These are mute output jacks The black jacks RX4 RX7 are normally closed and open when the connected receiver is muted The red jacks RX1 RX3 are normally open and close when the connected receiver is muted Voltage and current limitations of the jacks see Specifications should be observed 7 AC Power Connector 115 VAC or 230 VAC is connected here using an ordinary IEC computer type power cord The Multicontroller is internally fused and the user is responsible for verifying that the appropriate fuse 1 4A for 115 VAC or 1 8A for 230 VAC is used Note that 230 VAC operation is only possible if a dual primary power transformer Stancor DSW 520 was installed during assembly III General Instructions and Precautions 1 Up to eight receivers may be connected to the multicontroller although only se
4. itch Switches between two possible receive antennas a 50 Q coax fed antenna connected to the rear BNC antenna input and a high Z antenna connected to the rear RCA phono jack high Z antenna input The nominal input impedance of the High Z port is 1000 Q It is not recommended to leave this switch in the high Z position if nothing is connected to the high Z input because of the potential for parasitic oscillation of the multicontroller s internal amplifiers Oscillation will not damage the Multicontroller but may cause interference or noise with the connected receivers 3 Preamplifier Switch Enables a 12dB broadband internal preamplifier when the 50 Q antenna input is selected The preamp can only be enabled when using the 50 Q antenna input Because the preamplifier reduces the headroom of the internal amplifier stages by 12 db it is best not to use it unless it is needed to hear weak signals 4 Mute Enable Switch Activates the back panel mute control jack When the switch is ON grounding the mute control jack mutes all connected receivers and turns off their associated LEDs When OFF the mute control jack is disconnected However connected receivers can still be muted manually by turning OFF their Receiver Enable switches 5 Receiver Enable Switches 7 Individually enable unmute their corresponding receivers When OFF the associated receiver is muted However even when enabled all receivers can be muted simultane
5. nformation about any receiver s mute requirements can be found in the receiver s instruction manual Note that some receivers made in the 1950s and earlier have a front panel Standby Switch which is in parallel with rear screw terminals These terminals are intended to be opened by contacts on an external antenna relay such as a Dow Key relay in order to provide muting capability In some designs the Standby Switch and external contacts simply disconnect plate voltage from the receiver s tubes The multicontroller cannot be used to mute such receivers both because the plate voltage is too high for the multicontroller relay contacts and because the multicontroller always grounds or ungrounds the mute line which would short to ground the recieiver plate voltage For such receivers users should use an external relay to mute the receiver with the multicontroller controlling the external relay s coil IV Specifications 1 Frequency Range 50 Ohm input Hi Z input Amplifier Circuits 0 1 MHz 55 MHz LF filter not installed 1 8 MHz 55 MHz LF filter installed 0 1 MHz 55 MHz 2 Voltage Gain nominal per channel 1 0 0 dB 2 0 6 dB 50 Q load preamp off no load preamp off There is a broad 3 dB peak in the response from 40 60 MHz 3 Typical 3 dB Bandwidth 0 025 MHz 72 MHz 1 8MHz 72 MHz 4 Antenna Input 50 Q Impedance Clipping threshold Connector 5 Ant
6. ously by grounding the rear panel control jack provided the Mute Enable Switch is ON 6 Overload Indicator This indicator lights when RF voltage on the receive antenna exceeds about 1000 mV When lighted all enabled receivers are muted and antenna outputs RX1 RX7 are disabled The Aux Output always remains active Note that the overload threshold is reduced by 12 db when the preamplifier is turned on Normally the overload LED will flicker before the overload relay actuates thus providing an indication that overload conditions are being approached II Rear Panel Connections 1 50 Q Antenna BNC Jack A coaxial fed receive antenna is connected to this jack The input ice is a resistive 50 Q DC voltages on the antenna should not exceed 50V and RF voltages should not exceed 3 5 Vrms 2 Hi Z Antenna Phono Jack A single wire antenna is connected to this jack which has a nominal 1000 Q input impednace Voltage precautions are the same as for the 50 Q antenna 3 Control Phono Jack Grounding this jack simultaneously mutes all the enabled receivers provided the Mute Enable switch is ON Normally the jack would be controlled by the PTT line or Relay line of the operator s transmitter or transceiver If external control is not used then a shorting plug should be placed in the jack to allow all receivers to be muted simultaneously with the Mute Enable switch 4 RX1 RX7 BNC Jacks These are buffered receiver outputs eac
7. ven of them may be muted BNC cables having a nominal 50 Q impedance should be connected from ports RX1 RX7 or the Aux Out port to the antenna inputs on the receivers If the connected receiver s antenna input has 50 Q impedance then the signal from the multicontroller will have the same strength as the signal appearing on the receive antenna gain of 0 dB Receivers of the vacuum tube era or inexpensive modern receivers may have screw type antenna terminals whose impedance is greater than 50 Q If this is the case signals from the multicontroller may appear up to 6 dB stronger voltage gain of x2 than the signals on the antenna depending on the receiver s actual input impedance 2 Ordinary shielded phono cables should be connected from the seven mute output jacks under the RX1 RX7 BNC connectors to the mute inputs of the connected receivers The black phono jacks RX4 RX7 are normally closed outputs which open when the receiver is muted This open to mute convention is the most common and is used for Drake Collins Hallicrafters and most other receivers of the vacuum tube era Military receivers such as the R 390 and R 390A and so called premium receivers made by Racal Watkins Johnson Harris and others typically use a close to mute convention and should be connected to the red phono jacks RX1 RX3 The user can reconfigure any of the mute jacks as close to mute or open to mute by changing jumpers on the main circuit board I
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