Figure 1 – low pass filter design – Communication Concepts EB63A Construction Hints User Manual
Page 5
relay will drop out. Also the relay may drop in and out during SSB operation if the
relay hold delay is not long enough.
2. Relay locks up – this could be caused by a variety of problems but is usually caused
by the large output signal feeding back into the input. This can be caused by
improper grounding of the input and output signal coax, running the coax too close
together (don’t tie-wrap the two together), or the routing of the coax signal lines.
3. The RF transistors get very hot with no RF signal input – too large a bias voltage on
the base of the RF transistors usually causes this. Check the bias voltage with a
digital voltmeter. It should be between 0.60 and 0.69 volts.
Figure 1 – Low Pass Filter Design
5
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