The EC10 communications receiver

  
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One thing we should keep in mind is that the EC10 is now a vintage receiver, it has collector appeal. Any-thing we do should really be carried out in a manner that preserves the original state, most of the following adheres to this. Things like replacing all of the Germanium transistors with Silicon devices could be done but this would be considered a radical modification. I have however,
The EC10 communications receiver - schematic

carried out some tests using a Silicon RF transistor as a replacement for the original Germanium transistor in the 1st RF amplifier. More on this later. The first and most basic thing you should do is replace all of the electrolytic capacitors, as many older types of electro`s are notorious for leakage. Make sure you observe operating voltage and polarity. The BFO circuit was only intended for use with CW and even here a strong signal can cause problems, there`s just not enough coupling. To fix this problem and make SSB reception possible, you need to change C-67 on the IF / AF board from 1pF to 10pF, preferably polystyrene. The result will be a greater level of BFO carrier coupling into the IF. You will need to use the BFO and tuning controls together as to much BFO carrier will swamp weaker signals, (keep AGC on) the fine tune on the later Mk-2 becomes quite useful here. A distinct disadvantage of the EC10 is the lack of an internal mains power supply, there is enough space to add your own but a few points need to be made. Current consumption with the lamps on is around 200 to 250 mA maximum at 9 Volts and regulation of this voltage is recommended as the internal zener regulator is slightly sensitive to input variations. I recommend the use of a small toroidal mains transformer, conventional I-E type transformers are larger and suffer EM field leakage that may cause "Hum" problems. To mount a transformer and supply...



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