crystal filter pitch differences
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Hello to all. First time posting herem glad to be a part of the Elecraft family. I have a K1, K2, xg-1. the K2 is having a problem with pitch differences, one bfo setting to another, the hard part is that sometimes it's perfect, other times not. Normally if there is a pitch difference, opt-1 is different. I have tried several times to get it correct but no success. I have used Spectrogram also.. Any suggestions?? thanks. Tom km4cu
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RE: crystal filter pitch differences
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Tom km4cu wrote:
Hello to all. First time posting herem glad to be a part of the Elecraft family. I have a K1, K2, xg-1. the K2 is having a problem with pitch differences, one bfo setting to another, the hard part is that sometimes it's perfect, other times not. Normally if there is a pitch difference, opt-1 is different. I have tried several times to get it correct but no success. I have used Spectrogram also.. Any suggestions?? ------------------------------------------ Is it a new K2 Tom? (Or at least with a s/n >3000). Some pitch variation is normal. The digital circuits that reset the BFO frequency to that set up during CAL FIL have a resolution, or accuracy, that allows perhaps 20 or 30 Hz. However, it is generally stable from day to day. Older K2's had a BFO that drifted more than the current ones. The BFO, like any oscillator designed to change frequency, tries to change frequency on its own, usually in response to temperature changes. You may be experiencing some BFO drift if the degree if change when stepping through the filters varies from time to time. The drift issue with the older K2's was cured with a mod kit from Elecraft. The normal method of reducing the filter-to-filter variation to the minimum possible - assuming no BFO drift - is to force the K2 logic to re-read the BFO frequencies. You do that by putting the calibrator probe in the BFO test point like you did when running spectrogram, go into CAL FIL, and then change each BFO frequency setting to and different value, then put it back where it was. That movement causes the logic to re-read the BFO frequency and store a new, hopefully more accurate, value in memory. One thing to keep in mind is that you can *not* "tweak" the frequencies in CAL FIL while listening to a signal on the air. Only have noise in the bandpass. That's because the BFO and Local Oscillator (PLL Oscillator) frequencies interact to make changing the BFO frequency appear to make the I.F. bandpass move. There a good write-up on that on the Elecraft web site called "The Mechanics Behind CAL FIL". Ron AC7AC - _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: crystal filter pitch differences
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In reply to this post by tom-239
Tom,
If the pitch difference is 20 Hz or less, you have hit the 'best you can do' point. The DAC quantization error is about that size. Some folks claim that you can use techniques like modifying the filter width a bit to cure it, but I have never tried it, and for my purposes, it is just not worth it - after all a shift of only 20 Hz, while perhaps disconcerting, will still be well inside the passband (assuming you have the narrow filters properly contered on you sidetone and you are tuned to zero-beat). If you have a large shift, then there is something awry with either the K2 or the way you are interpreting the Spectrogram display. 73, Don W3FPR > -----Original Message----- > > Hello to all. First time posting herem glad to be a part of the > Elecraft family. I have a K1, K2, xg-1. the K2 is having a > problem with pitch differences, one bfo setting to another, the > hard part is that sometimes it's perfect, other times not. > Normally if there is a pitch difference, opt-1 is different. I > have tried several times to get it correct but no success. I have > used Spectrogram also.. Any suggestions?? thanks. > > No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.10.2 - Release Date: 4/21/2005 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: crystal filter pitch differences
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In reply to this post by tom-239
Tom: You're never going to get rid of some small pitch change: 10-20Hz
is within the resolution of the D2A conversion. It is something you can learn quite easily to live with, if you will allow yourself. It is something that will drive you crazy if you won't allow yourself. Because the pitch shift is really and truly inconsequential, allow me to suggest you do yourself a favor, and forget it. best wishes, dave belsley, w1euy On Apr 24, 2005, at 5:16 PM, tom wrote: > Hello to all. First time posting herem glad to be a part of the > Elecraft family. I have a K1, K2, xg-1. the K2 is having a problem > with pitch differences, one bfo setting to another, the hard part is > that sometimes it's perfect, other times not. Normally if there is a > pitch difference, opt-1 is different. I have tried several times to > get it correct but no success. I have used Spectrogram also.. Any > suggestions?? thanks. > > > Tom km4cu > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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