+++++++++++++++++++++++++++++++ See also K2 BFO CW Reverse Notes +++++++++++++++++++++++++++++ Subject: Re: [Elecraft] VCO Calibration All, > Because the K2 filters are so good, actually attempting to zero beat WWV > is quite problematic. It is much better to match beat tones. Let's say > you've got your side tone set to 680Hz. Then, if you listen to WWV with > the mode set for cw, when the beat tone from WWV matches your side tone, > the display ought to be close to 10000.00. If you use the L mode, when you > match the WWV beat tone to your side tone, the display ought to be close to > 10000.68. Exactly the way I ended up doing it. Mike VP8NO #1400 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Subject: Re: [Elecraft] VCO Calibration For what it may be worth, my Zero Beating demo has been MOVED FROM my web site to the Elecraft Web Site, Builder's resource Page http://www.elecraft.com/Apps/zerobeat.htm. The demo includes two WAV files which are somewhat larger (300kB-500kB) than most other files there, so it'll take a little while to download them. 73 - Tom Hammond N0SS ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Subject: Re: [Elecraft] VCO alignment K2'ers with VCO questions, It is better to have the VCO voltage near the upper limits, as it avoids the highly non-linear portion of the varactors when they are near minimum tuning voltage and maximum capacitance. That can cause some PLL linearization problems or erratic tuning, increased PLL tuning noise, etc. As long as you do not get too close to the 8 volt regulated limit, the higher the VCO voltage is - the better. Try to keep it below 7.0 to 7.5 volts at 4000kHz, to allow adequate high tuning range safety factor should the VCO voltage change slightly over time with component aging, etc. The VCO voltage is less than that value, on most any other band or frequency. A VCO setting 6 volts at 4000kHz is a good compromise, for consistent CAL PLL linearization and some limited general coverage receive range. If you aren't interested in out-of-ham band coverage, you can set the VCO voltage a little higher, at the 7.0 yo 7.5 volt range at 4000kHz. Be aware though, the higher the VCO voltage - the more restricted your out-of-ham band tuning will be in some cases on different bands. On some bands the VFO is added to the incoming signal to produce the IF, while on others it is subtracted. See the chart in the manual at the beginning of Appendix B to understand this. There is a "window" of VCO tuning voltage that is preferred, for complete ham band coverage and some limited SW general coverage. Several factors are at play here, so follow the suggested settings of VCO voltage as shown in the manual and do not set it either too low or too high for these reasons. 73, Gary Surrency AB7MY Elecraft Technical Support ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Hi All, Just a note to say thanks to those who replied (many) to my problem with C22 not having enough range to align to my frequency counter. I was able to fix the problem by adding an 18 pF capacitor across the trimmer. I just mounted it on the under side of the control board. Now all is well in K2 land. Thanks for the suggestions and help. Regards, Jeff Weinberg W8CQ K2 #1617 w8cqjeff at ameritech.net +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >The second part of my question, how would I know if I am zero beat with a >signal like WWV so I can use this signal to calibrate my K2's internal >frequency counter? Does this merely mean to tune for strongest received >signal? Tuning for the strongest received signal will probably NOT work... esp. for frequency calibration. WWV is kinda difficult to use for this type of adjustment because most of the time it transmits an audio tone (500Hz, I am told) AS WELL AS its normal carrier signal, so you MUST ensure that you are tuning to the CARRIER signal and not the audio tone. To do so properly, you tune in the WWV CARRIER such that the tone you hear from it is identical to the K2s sidetone (using the SPOT feature). When the two tones match, the frequency indicated on the display is that which the K2 'thinks' it's receiving on. Each time you tweak C22, remember to do another CAL PLL on 10MHz. This must be done or your tuning will not properly follow the changes made to C22. If my theory works right, I believe as you tune THRU the WWV signal, the first 'signal' you should hear will be that of the 500Hz tone they usually transmit... if you continue to tune further away from the signal, you should begin to hear a second signal. THIS should be the carrier and is what you want to match against your sidetone. There are certain times of each hour (maybe the last 5 minutes of the hour) where no tone is transmitted, just the carrier. This may prove easier to use, but since it lasts only a short while, it'll probably not be long enough for you to complete the adjustments. Hope this helps. 73 - Tom Hammond N0SS _____________________________________________________________ From: Stuart Rohre Subject: Re: [Elecraft] WWV tone sequences vary Actually, WWV has had charts in some of the ARRL Handbooks, (and probably on the NIST web site), showing the times they transmit various tones, including the note A, 440 Hz, of the musical scale. There is sub carrier modulation of a digi sort at some times, thus a full chart of each minute should be used to find when to listen for a carrier, or carrier and one tone or no tones,etc. 72, Stuart K5KVH +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ From: gsurrency at juno.com Subject: [Elecraft] RE: CAL C22 Hi K2'ers, Please note that when you replace the top cover with the speaker in it, the magnet influence on the frequency may be a considerable factor. Always set the top cover in place when you are trying to zero beat with WWV at 10MHz, and note the difference between the K2's LCD readout and the actual WWV frequency (10000.00kHz). Then you can remove the top cover to access C22 on the Control Board, run CAL FCTE and set C22 to compensate for the freq. readout error. Move C22 in the opposite direction of the freq. error from WWV, watching the change in CAL FCTR readout from its original reading. Replace the top cover, run CAL PLL again, and then see if you got C22 to the correct setting. Repeat this procedure as necessary until you are satisfied with the results. I noted as much as a 50Hz shift when I installed the top cover recently on a repaired rig *after* I thought I had C22 set perfectly. Had to do it all over again.......:-( Also remember that the bottom cover should be installed any time you are doing CAL PLL or CAL PLL. This will prevent the same kind of frequency shift and error if you forgot to do these calibrations with the covers off. 73, Gary Surrency AB7MY Elecraft Technical Support +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ The way I check the calibration is by tuning in WWV at 10 MHz on USB and LSB and centering the tuning so the tone being broadcast is the same (or within the 10 Hz resolution of the dial) on both sidebands. The CW BFO setting is then confirmed by hitting the SPOT button in CW mode and seeing that the sidetone is zero beat (within the same 10 Hz resolution) without changing the tuning dial. On mine, the calibration at 10 MHz moves about perhaps 20 or 30 Hz over many hours (or days) as the sun shines through the window, etc. In my experience, that is typical for a crystal-controlled oscillator that is not temperature-controlled oven. It is a 'very' slow movement. One time, in a frenzy of useless arm-waving, I recalibrated my K2 at 10 MHz using WWV because it was consistently a whole 20 Hz high. Got it right on. (If you do that, first measure how much taking the cover with the speaker off of your K2 changes the calibration. It does affect it. Gary Surrency reported that he found one that moved 50 Hz by removing the cover). It only took me a couple of hours to get it 'dead on' by the time I also rechecked all the BFO frequencies and got the uP to update all the settings for the filters. The next day I was 10 Hz low . I decided that it was more fun to operate the thing than to calibrate it! I guess that's why the tuning knob is right there on the front panel and C22 is buried under the crystal on the inside. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Got C22 set right now Thanks to STEVE, GARY, TOM, and others... HERE IS WHAT i DID set k2 to 10.000.00 lsb set up spectogram set offset tone for 440hz Turned on spot tuned k2 for zero beat on spot monitored spectogram and 440hz tone on wwv noted readout diffference from wwv on k2 used the internal counter and tp1 to offset freq ran cal pll ran cal fil on filter one (the one I was using) turned on spot and re-zero beated looked at spectogram to help me find zero beat made one more correction and repeated procedure the wwv zero beated at 10.000.00 on the k2 readout... the 440hz spot was directly over the 440hz wwv tone I turned the spectrogram calibration to .7 hz accuracy and re-checked the freq readout on the 440hz tone... from wwv I was less than 3hz off... no way to correct that when my receiver jumps in 10hz steps is there? I then followed the book procedure for the other bands and filters.. now 7.228 os 7.228 and 14.230 is 14.230 and 3.863 is 3.863 amazing what happens when one finally does something right... I don't think I will take the top off the k2 for a long time now...I've done caused myself enough grief... and now the grief - relief... meaux jeaux... I is on freq once meaux... ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: 11 Mar 2001 07:44:08 MST From: Murphy Chesney Subject: [Elecraft] re: Calibration question Vic - I had the same problem with C22, initially the K2 would calibrate using WWV 10MHZ right at the top of c22's capacity. Eventually though there was enough internal drift (after a year or so) so that I was 120 HZ off and couldn't get there with just c22. I finally put 47 pF across c22 and it gave me all the range I needed, so far without any bad side effects. Your milage may vary and I certainly wouln't go higher as the original c22 is just 50 pF. Let us know if you find a nifty way to get more range out of c22 since I prefer not to resort to "unauthorized" K2 mods!! 73's Sandy, KB3EOF K2 sn 904 +++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 12 Mar 2001 07:46:10 -0800 From: Vic Rosenthal Subject: Re: [Elecraft] re: Calibration question Murphy Chesney wrote: > Let us know if you find a nifty way to get more range out of c22 since I > prefer not to resort to "unauthorized" K2 mods!! Well...I spent the entire day and much of the night fiddling with c22, running CAL PLL and CAL FIL, fiddling some more, etc. I learned that you can move the range lower by adding a small capacitor across c22, you can move it higher by reducing the value of c21, and that the original parts were the right ones for me! The way I finally got it right was to match the pitch of the spot tone to wwv, and take the difference from 10 Mhz. Then I read the frequency of the VCO with the internal counter, subtracted the error, and changed c22 until the VCO showed the new value. Then I ran CAL PLL. When I checked wwv it was usually correct at this point; however, running CAL FIL threw it off a bit. So I repeated the process. After a few iterations, it came out right, and then I ran CAL PLL on all of the bands. Now my K2 is within 10 or 20 Hz of my TS850 in most places (and spot on with wwv at 10 Mhz). And I'm bloody tired of c22! 73, Vic, K2VCO Fresno CA ++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 12 Mar 2001 20:00:51 -0800 From: "Ron D'Eau Claire" Subject: RE: [Elecraft] re: Calibration question Vic, K2VCO wrote: "Now my K2 is within 10 or 20 Hz of my TS850 in most places (and spot on with wwv at 10 Mhz). And I'm bloody tired of c22!" Brings back memories for me and a bunch of readers, I'm sure, Vic. There was a time I didn't get on the air for several sessions at the rig, between fiddling with the calibration of the dial and using Spectrogram on the filters. Almost considered welding the case shut so I could get in one uninterrupted operating session! You did *very* well getting that close, since the DAC's used in the K2 introduce a built in 20 or 30 Hz error that can't be 'tuned out' on purpose. Ron AC7AC K2 # 1289 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 4 Apr 2001 07:08:03 -0400 From: "Carl Morris, WN3DUG" Subject: [Elecraft] RE: K2 VCO Alignment Problem Stan, K8SB, I had the same problem. Gary suggested checking T5 and spreading out the turns or removing 1 turn. I did both and found that removing 1 turn worked for me. Good Luck! 72/73, Carl, WN3DUG K2 S/N: 01320 +++++++++++++++++++++++++++++++++++++++++++++++++++