[Elecraft] Problem with newborn KRX3: Very poor sensitivity.

[Jon Kåre Hellan]

I have installed the subreceiver in my K3 and done some testing. It 
seems to work, except that sensitivity is very poor. I've been listening 
to one receiver in each headphone. On the sub-rx. the strongest signals 
on the band just come up above the noise. The effect is much stronger 
than swithing the attenuator in and out.

I've gone over all TMP cables carefully, and had the sub-rx in and out 
of the K3 several times. Behaviour has been the same every time.

To compare sub and main signals, I linked the two VFOs. Both RF gains 
were at max. Signals which were clear with the main AF gain at 7 - 8 
o'clock became audible just above the nose at 3 o'clock AF gain on the sub.

To check that I was actually hearing the sub-rx, and not some kind of 
crosstalk from the main, I unlinked the VFOs and verified that what I 
heard in the sub-rx tuned with the main. I also checked that it 
responded to sub-rx width and offset tuning, and not to main.

With a strong signal, I moved the same antenna between main and aux 
input and found that signals from both sounded about the same on the sub-rx.

I've varied bandwidth from min to max. It switches between filters as 
expected, and there are no sudden changes in signal level.

To me it sound like the problem must be either on the KRX3 board or on 
the way out from there. 2 independent signal inputs give the same 
result, so they're either both OK or both bad in exactly the same way. 
If there was anything wrong with the cable from the synthesizer board or 
the one from the frequency reference, I wouldn't expect the sub-rx to 
work at all. Does this make sense?

Suggestions, anyone?

73
Jon LA4RT

Jon Kåre Hellan, Trondheim, Norway