Deaf KX-1 - repost
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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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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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 <[hidden email]> 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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Stephen,
Since the KXB3080 is already installed, check the number of turns carefully on L1, L2 and T2 to make certain you do not have an extra turn. T2 has 33 turns on the red winding, and L1 and L2 each need 9 turns on the green winding (the red winding is only used on 80). All else remains the same. 73, Don W3FPR Stephen Prior wrote: > 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 <[hidden email]> 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:[hidden email] >> >> 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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Well Don, I'm hoping I've found the problem. In removing the atu board
as part of the strip down to check toroids etc, I noticed that the pin of P1 nearest the side of the kx1 on the atu board appeared unsoldered. In the many times I have had this unit apart I had never noticed this before. Fortunately, although many miles from home in a foreign land, I have a miniature butane powered iron in the toolkit in the car. I even found some solder! The rx sounds much livelier now and I am seeing more power output! Thanks for the advice anyway. I probably would not have opened the radio up again to look were it not for your suggestions! 73 Stephen On Thursday, July 15, 2010, Don Wilhelm <[hidden email]> wrote: > Stephen, > > Since the KXB3080 is already installed, check the number of turns carefully on L1, L2 and T2 to make certain you do not have an extra turn. > T2 has 33 turns on the red winding, and L1 and L2 each need 9 turns on the green winding (the red winding is only used on 80). All else remains the same. > 73, > Don W3FPR > > Stephen Prior wrote: > > 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 <[hidden email]> 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:[hidden email] > > 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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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