[Elecraft] [K3] KRX3 low on gain

[Phil Daniells]

Hello.

For a while now I've had the feeling that my sub-receiver has been a bit 
'quiet', when compared to the main Rx, requiring its AF gain to be 
cranked up to compensate.  However, I'd not really worried too much 
about this as its ability to hear weak signals was not impaired.

Yesterday, I finally got round to measuring the audio levels coming out 
of my K3 and found the following:

1)   The audio output of the KRX3 was -16dB compared with the main Rx 
(AGC inoperative, 5uV from signal generator).

2)   The -16dB disparity was there regardless of which KRX3 antenna 
input was in use.

3)   The problem is neither band nor mode dependant.

4)   The problem occurs with both the 2.7kHz and 400Hz roofing filters.

4)   When listening to a 'real' signal the KRX3 is operating lower down 
the AGC characteristic than the main Rx.

5)   Adjusting the individual filter gains did not do enough to compensate.

The fact that my KRX3 is not 'deaf', but just low on gain, suggests that 
its front-end is OK and that the fault is further down the chain.

The AGC observations, in turn, suggest to me that the gain deficit is 
occurring after the front-end, but before the point at which AGC is 
derived (and not in the audio stages).

I have already removed and re-installed the KRX3 and its leads, but to 
no effect.  Before I resort to a serious stripping-down of the K3, does 
anyone have any experience of a similar fault, please?


73,
de Phil, GJ4CBQ.