I re-ran the IMD tests with another PS and put 30 db more attenuation in front of the spectrum analyzer and the K3 now looks good above 65 watts. -30 db IP3 at 100 watts, in fact. Sorry. But it's still cleanest down in the 30 watt range. Rick K2XT
> From: rstea...@hotmail.com > To: elecraft@mailman.qth.net > Date: Tue, 1 Sep 2015 15:18:05 +0000 > Subject: Re: [Elecraft] K3S IMD Questions > > I have been playing with a Flex 6300 here in my shack recently. I consider > it a great piece of test equipment for analyzing signals in the shack as well > as on the air. It does everything and more, as a spectrum analyzer, that my > old HP141 analog setup did, except it doesn't have a tracking generator. > My measurements are not completed and I am still experimenting, but here is > what I've done so far. Phase noise, cw transmitted bandwidth, and 2 tone IMD > tests. My two rigs are a K3/100 and an FT100D (how good, and how bad can you > get!) > Using a Flex 6300 as a spectrum analyzer, I fed a greatly attenuated signal > into it, keeping the level just under 0 dbm, and assuming it is not > generating imd of its own, but I haven't quantified that yet. > Phase noise tests - I was interested in seeing if it could display the > RELATIVE benefit of the new synthesizer on my K3, looking at phase noise. > Here are PRELIMINARY RELATIVE results, without numbers, in order of phase > noise level at 2 khz separation:An 8640B signal generator (known to have low > phase noise)The K3 with original synthesizerThe FT100 After I install the new > synthesizer I hope to be able to compare it to the original one. > I verified the FFT spectrum analyzer (Flex 6300) can give an instant view of > transmitted bandwith of the cw signal sending fast dots. MUCH easier and > better than the old analog HP spectrum analyzer which had to sweep extremely > slowly across the band with a narrow filter. With this setup you hold the > key closed, and hit the control-print screen buttons on the keyboard and you > have a beautiful picture ! Ain't technology great? > 2-tone IMD measurements -The two tone test of the K3 showed something > interesting, since it has both 10 watt and a 100 watt PAs installed. > Starting with low power and cranking up the power control, you notice, of > course, that the ten watt PA has worse IMD just before the big PA kicks in, > in the 11-12 watt range. Then it is very clean (approximately -40 db for > third order) at its best, and ok in the 30 watt range (where it would be set > to run my 8877 amp) but then gets quite ugly above 65 watts. And I mean in > the -20 db range at 100 watts. IF it was overloading the spectrum analyzer > these tests would be invalid, so I need to verify that. As I said these > tests are preliminary. I need a few more hours. > > In my humble opinion, running at full power, 100 watts barefoot, my K3 would > be transmitting an unacceptably sloppy signal. Keeping it in the 65 watt > range or under, or driving an amp would be better, provided your amp is > clean. My 8877 amp is VERY clean. I don't know about a solid state amp. > Some of the ugliest signals I have seen on the bands with the Flex panadapter > in very limited observations have come from Expert 1500 watt amps (2 > examples). The very best was an Anan 100 with a Ten Tec 1500 watt tube amp. > The waterfall was a brick wall - NOTHING whatsoever outside the 3 khz > bandwidth. > Rick K2XT > > > > > > ______________________________________________________________ > 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 > Message delivered to rstea...@hotmail.com ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
