Many thanks Don, I shall have to wait until my return home for a scope but I shall certainly have a close visual inspection. I should have added however, that the radio has both the 30/80 board and the auto atu - I don't know whether that will change your diagnosis.
73 Stephen On Thursday, July 15, 2010, Don Wilhelm <w3...@embarqmail.com> wrote: > 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 > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
