BC624 - SCR522 Receiver

BC624 - SCR522 Receiver

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Technical Data

The BC 624 is a single conversion, crystal locked, 4 channel receiver, operating in the frequency range 100-150 mc. It was designed for remote control only. The set has a sensitivity of 3 to 4 microvolts for a 10db s/n ratio.

It is possible to convert the receiver to a free running oscillator, but there are mechanical problems to be overcome as the oscillator and RF shafts need to be combined and a calibrated dial provided. As the receiver is AM, listening to aircraft is about the only use for the set unless it is converted to FM. Bandwidth of the I.F. is around 120 kc.

The tubes used include 12J5, 12C8, 9002, 9003, l2AH7 and 12SG7's.

The set has relay operated squelch. Some models had electronic squelch and 12H6 noise limiters.

The rack mounting is needed to provide mechanical drive to change channels. BC624 front end

The following formula is used to find the receiver crystal frequency:

F= fr - 12 (The I.F.) x 1000, divided by H

    fr = frequency to be tuned in mc
   H = crystal harmonic frequency

The crystal harmonic is frequency selected from the table below:
H is
    11    I00 -108 mhz
    12   108 -116 mhz
    13   116 -124 mhz
    14   124 -132 mhz
    15   132 -140 mhz
    16   140 -148 mhz
    17   148 -156 mhz

Audio output is from transformer 295. Terminal 5 is 50 ohms, 6 is 300 ohms and 7 is 4000 ohms.

The overall range of the transceiver is 180 miles at 20 000 feet.

Illustrations of the set

BC624 top BC624 bottom

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© Ian O'Toole, 2009. Page created: 28/04/03 Last updated: 4/12/2009