For a comparison point, you might wish to look at my K2 stability measurements at http://www.cliftonlaboratories.com/k2_freq_stability.htm
Jack K8ZOA On 1/20/2010 8:58 AM, Don Wilhelm wrote: > Doug, > > The BFO is obviously the culprit here. > What serial number is this K2? > Do you have the new L33? with many turns of #36 wire. If this is an > older K2, install the BFO upgrade kit. > If you already have the upgraded parts, then I suggest you equip > yourself with all of the parts in the BFO circuit and just replace > them. You can replace them one at a time until you find things more > stable, but I believe it is easier to replace them wholesale and see > what happens. You will need > 2 BFO crystals X3 and X4 > C173 and C174 > D37 and D38 > L33 > Replacing L33 will require a high value 1/8 watt resistor to mount the > toroid - the K2 lists this as R116 PN E500086. > > 73, > Don W3FPR > > Douglas Furton wrote: > >> Hello, all >> >> I've been bothered with the CW tone/filter setting >> on my K2 for some time now. I seem to need to run >> CAL FIL daily, at least to have the BFO freq. read >> into memory. I observe that the CW tone starts low >> and drifts upwards as the rig warms up when I tune a >> signal to the center of the filters (maxing the >> S-meter). >> >> Here is some data characterizing the freq. drift >> in my K2 (#6761). I measured the PLL and BFO freqs >> with a nice frequency counter. I measured these >> shifts with the K2 locked at 7050 kHz, and computed >> the total shift = dPLL - dBFO (all referred back to >> the initial (T=18.5C) measurements. I measured the >> temp. with a thermocouple in contact with the PLL >> thermistor board. I also measured the PLL and BFO >> control voltages at various times and found them >> to be constant. >> >> >> Cumulative freq. Shifts >> T PLL BFO Total >> (C) (Hz) (Hz) (Hz) >> 18.5 0 0 0 >> 19.3 9 -17 26 >> 19.6 13 -34 47 >> 20.2 17 -57 74 >> 20.8 19 -70 89 >> 21.3 24 -79 103 >> 21.6 26 -87 113 >> 22.0 28 -92 120 >> 23.3 37 -124 161 >> 24.0 40 -136 176 >> 24.5 46 -164 210 >> 25.0 53 -205 258 >> 25.5 62 -256 318 >> 25.5 70 -310 380 >> >> (I hope the table above remains tabulated >> properly. Best viewed with a monospace >> font.) >> >> It seems the thermistor board compensates the PLL >> fairly well (although maybe I could tweak RA upwards >> a bit), but the BFO drifts considerably, and >> since the PLL and BFO drift in opposite directions, >> the total drift is exaggerated. >> >> I may measure the drift on a second band, but these >> data are just from 40 m. >> >> I would really like to improve the temp. stability >> of my K2. >> >> Does anyone have any suggestions? >> >> Thanks, >> >> Doug Furton >> K8EXB >> >> ____________________________________________________________ >> GET FREE 5GB EMAIL - Check out spam free email with many cool features! >> Visit http://www.inbox.com/email to find out more! >> ______________________________________________________________ >> 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 >> ------------------------------------------------------------------------ >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 >> 02:34:00 >> >> >> > ______________________________________________________________ > 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
