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Hi Julian. You should be seeing readings around -30 or better.
Are you using PSK-D with the paddles or a soundcard program with Data-A? Set your soundcard output level to about 30-40%. Then with the K3 in Data/Data-A mode start with the line-in gain at 1(MIC gain control becomes Line-in control in data mode). Set your power to about 25W and while sending some text adjust the line in gain so that you have about 3 bars of ALC. The only thing I have seen that causes excessive IMD is overdriving either the soundcard output and/or too much line-in gain. 73 Greg AB7R On May 2, 2009, at 8:16 AM, Julian Moss wrote: > Hi! > > I have a problem with my K3 S/N 222. I have just begun using my K3 on > 10m PSK31 after getting interested in using the PSK Propagation > Reporter to detect sporadic-e openings. > > I was making only my second contact on 10m PSK31 this afternoon and > the station I was working gave me a very poor IMD report. I switched > on my KK7UQ IMD meter and sure enough the IMD was very poor, not quite > as bad as the station reported but showing values such as -15dB etc. > > IMD is still very good on the higher bands (I did not check 24MHz > because I don't have an antenna for it) so I do not think this is a > fault that has suddenly developed. > > It is not a problem with RF feedback on 10m because I checked the IMD > whilst using my DL1 dummy load and it was still unacceptably bad. > > It is not a problem with the KK7UQ meter giving false readings on 10m > because it shows readings in the -30dB region when I use another radio > on 10m. > > It is probably not a problem with the KPA100 because the bad IMD > readings occur even at 5W (and even lower) power level. > > It is probably not a new problem, as I have hardly ever used the K3 on > 10m since I had it, and never on PSK31 on 10m, so no-one would have > noticed it before. > > Is there anything that can be done, bearing in mind that the only test > equipment I have that can show the IMD is the KK7UQ meter? > > 73, > > Julian, G4ILO > G4ILO's Shack: www.g4ilo.com > G4ILO's Blog: www.g4ilo.com/blog.html ... [show rest of quote] ______________________________________________________________ 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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I was in contact with Julian yesterday and the problem seems to be
related to the computer sound card to line in/out cable. He's not sure at this stage if it's rear panel grounding issues or not. Measuring my K3's 2 tone IMD using the internal 2 tone generator, gives 3rd order products of -33 dB relative to one of the two tones (or -39 dB as per the ARRL method of measurement) on 28 MHz at a power output level of 30 Watts. Julian was using a power level of 20 ~ 30 Watts. The figures are much worse when driving the low power PA hard at 10 Watts, or the high power PA at 100 Watts. 73 Dave, G4AON K3/100 #80 ================== >/ I was making only my second contact on 10m PSK31 this afternoon and />/ the station I was working gave me a very poor IMD report. I switched />/ on my KK7UQ IMD meter and sure enough the IMD was very poor, not quite />/ as bad as the station reported but showing values such as -15dB etc. />/ / ______________________________________________________________ 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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