Posted by
Don Wilhelm-4 on
Jul 15, 2010; 12:33pm
URL: http://elecraft.85.s1.nabble.com/Deaf-KX-1-repost-tp5296792p5297117.html
Stephen,
While the MDS of the KX1 is not quite as good on 20 as it is on 40,
there should not be such a substantial difference.
I would first suggest that you check the oscillator injection at the
mixer U6 pin 6 on 20 meters - it must be greater than 200 mV peak to
peak (70 mV RMS) for the mixer to work at full capability. If it is
low, check the 14 MHz LPF for proper values and good soldering. Could
it be that one of the tiny inductors (L4 or L5) were "injured"?
The next step is to measure the MDS on both 40 and 20 using the XG2 and
the method outlined in the XG2 manual. How many dB down is 20 from 40?
Yes, the KX1 is not quite a sensitive on 20 meters as it is on 40, but
the 20 meter MDS should still be respectable - and should be better than
-126 dBm.
There is another "cure", and that is to add the KXB3080. The front end
of the receiver is changed with that option and has a higher Q than the
stock KX1 front end.
73,
Don W3FPR
Stephen Prior wrote:
> I never had a reply to my original posting from April, so thought I
> would fish for advice again.....
>
> What has prompted me to repost is a qso just a few minutes ago with a
> GW on 20m (I'm in south-west France at the moment) where he gave me
> 579 (I was running 3W) and I could barely hear him. In the end I lost
> him completely.
>
>
> Here's the original posting........
>
> I have always felt that on 20m the KX-1 is much quieter in terms of
> background noise compared with the 3 other bands. Having just bought a XG2
> on ebay, I have been comparing receive performance at the 1uV level between
> 40m and 20m. There's no doubt that the s/n ratio on 40m is better by
> several dB (not measured, so a subjective observation).
>
> I have checked the alignment by adjustment of the trimmers 20a and 20b and
> found that the tuning was already pretty much on the nose.
>
> So the question is, is there anywhere else I should look? I have checked
> both with and without the built-in ATU and reached the same conclusion.
>
> I'd be grateful for any pointers.
>
> Tnx and 73
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