Filters
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The filters in my K2 have always been a little weird. Tuning around,
the signal would always peak at the wrong point and then drop when it's at the correct sidetone frequency. I lived with it for a while. I finally took some initiative and tried it out with spectrogram and using the Elecraft noise generator. My findings were a bit suprising. The filter shape has multiple peaks and is not uniform at all.. compared to a few others I have seen. I compared it to another friends K2 and it was confirmed - my filter shape is funky. What should I do? Do I need to buy new crystals? Is something out of whack? Thanks, James Kern KB2FCV _______________________________________________ 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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Multiple peaks? At what bandwidths?
My K2 give nice flat filter shapes at bandwidths 1000 Hz and narrower. At SSB bandwidths, the filter passband has several or more very large peaks and has a gentle roll off in either lows (USB) or highs (LSB). Even at widths of 1.6 KHz the passband shows a couple of big peaks. In contrast my IC-735 shows a nice flat passband with no slope to it (thus proving the issue is not my PC sound card or the way I ran spectrogram). I did some screen shots and sent them to Elecraft support to see if it was a problem. No it's not. The Xtal filter was optimized for variable bandwidth over CW bandwidths and doesn't work as well at SSB widths. Apparently the fixed-width filter in the SSB adapter does not have this issue. Your post sounds like your rig is not "right". My rig has the new generation matched Xtal filters and I put in the 2nd set of grounding straps (per the instructions in the KSB2 documentation IIRC). Oh, and with spectrogram, I got much better results if I let it filter / average over 3 seconds or so. That really suppressed the noise and showed the filter shape more accurately. - Keith KD1E - - K2 5411 - -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of [hidden email] Sent: Tuesday, May 23, 2006 9:38 AM To: [hidden email] Subject: [Elecraft] Filters The filters in my K2 have always been a little weird. Tuning around, the signal would always peak at the wrong point and then drop when it's at the correct sidetone frequency. I lived with it for a while. I finally took some initiative and tried it out with spectrogram and using the Elecraft noise generator. My findings were a bit suprising. The filter shape has multiple peaks and is not uniform at all.. compared to a few others I have seen. I compared it to another friends K2 and it was confirmed - my filter shape is funky. What should I do? Do I need to buy new crystals? Is something out of whack? Thanks, James Kern KB2FCV _______________________________________________ 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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In reply to this post by James1787
James,
If your CW filter shows multiple peaks with the bandwidth at 1000 Hz and less, then yes, your crystals are 'funky' and should be replaced. Also, the SSB OP1 filter should have a smooth looking passband, but the wider widths with the variable filter will normally look very 'ragged' - although hey are usually useable for SSB reception if the passband is properly positioned. 73, Don W3FPR -----Original Message----- The filters in my K2 have always been a little weird. Tuning around, the signal would always peak at the wrong point and then drop when it's at the correct sidetone frequency. I lived with it for a while. I finally took some initiative and tried it out with spectrogram and using the Elecraft noise generator. My findings were a bit suprising. The filter shape has multiple peaks and is not uniform at all.. compared to a few others I have seen. I compared it to another friends K2 and it was confirmed - my filter shape is funky. What should I do? Do I need to buy new crystals? Is something out of whack? Thanks, James Kern KB2FCV -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.7.0/345 - Release Date: 5/22/2006 _______________________________________________ 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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In reply to this post by James1787
I took the K2 #2735 out of my storage case and played around a bit. I
got it hooked up to Spectrogram and followed the instructions in the PDF written by N0SS provided on the elecraft website. Most of the filters were dead-on. The only one that was off for CW was the 2.4 khz filter, which I adjusted. I sometimes use that filter so I can 'listen' to what else is on the cw band (I know, I'm weird..) I set the filters, in fact I changed my side tone from 750 hz to 600 hz. I was able to satisfactorily get the filters to work as they should. I used the Elecraft noise generator to create the necessary noise, and it has the SSB adapter in it. I discovered another strange phenonenom. I was listening to W1AW on 40 meters. If I recall correctly, their signal is on 7.0475 mhz. Well, if I zero beat the signal using the zero beat button, I found that it would zero beat on 7.04762 mhz. Come to think of it, for the longest time one of my friends would point out that my rig never seems to be on the frequency that I have on the readout (I'll tell them to go to a frequency.. they will and find that mine is off). It's been a long time since I have picked up the k2 building manual. Does it sound like my rig is off frequency? Is there a tuneup step or adjustment to make if it is off frequency? Thanks! 73, James Kern KB2FCV _______________________________________________ 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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James,
On my website http://3fpr.qrpradio.com you will find an article on K2 dial calibration. Follow the steps to set the 4 MHz oscillator, run CAL PLL and CAL FIL and you should be no more than 30 Hz off (you may have to go through the process twice), it is worthwhile. 73, Don W3FPR -----Original Message----- I took the K2 #2735 out of my storage case and played around a bit. I got it hooked up to Spectrogram and followed the instructions in the PDF written by N0SS provided on the elecraft website. Most of the filters were dead-on. The only one that was off for CW was the 2.4 khz filter, which I adjusted. I sometimes use that filter so I can 'listen' to what else is on the cw band (I know, I'm weird..) I set the filters, in fact I changed my side tone from 750 hz to 600 hz. I was able to satisfactorily get the filters to work as they should. I used the Elecraft noise generator to create the necessary noise, and it has the SSB adapter in it. I discovered another strange phenonenom. I was listening to W1AW on 40 meters. If I recall correctly, their signal is on 7.0475 mhz. Well, if I zero beat the signal using the zero beat button, I found that it would zero beat on 7.04762 mhz. Come to think of it, for the longest time one of my friends would point out that my rig never seems to be on the frequency that I have on the readout (I'll tell them to go to a frequency.. they will and find that mine is off). It's been a long time since I have picked up the k2 building manual. Does it sound like my rig is off frequency? Is there a tuneup step or adjustment to make if it is off frequency? Thanks! 73, James Kern KB2FCV _______________________________________________ -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.7.0/345 - Release Date: 5/22/2006 _______________________________________________ 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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