> The noise generator, designed by Tom Hammond N0SS, is an invaluable tool > for setting the filters in the K2. Don't forget that any noise bridge for antenna adjustment can do this job! +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Steve, This sounds like you have aligned your BFO for each filter on the wrong side of the filter center. If your sidetone is set to 500 Hz or so the TX offset will be 2 x .500 = 1 kHz as you noted. Set up your filters in CAL FIL with the K2 set to 40M. (Any band below 15 M is OK.) For CW normal, the BFO should be set BELOW your filter center and for CW-reverse your BFO frequency should be above the filter center. Both should be offset from the filter center by the amount of your sidetone. As an example, if your sidetone is set to 500 Hz, and FL2 400 Hz bandwidth filter center is at 4913.5, your BF1 BFO frequency should be 4913.5 - .500 = 4913.0 for CW-N, and 4913.5 + .500 =4914.0 for CW-R. (The filter center freq I picked is just for example. Your filter centers will be different.) 73, Eric +++++++++++++++++++++++++++++++++++++++++++++++++ Date: Thu, 19 Apr 2001 10:16:57 -0500 From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] Spectrogram Question Joel: >My question regards WHEN TO USE spectrogram. From the Builer's Resources >section on the Elecraft website, I gather that the appropriate place to >use Spectrogram is in the section of teh K2 manual entitled "BFO >Alignment" on page 60. You probably won't need to use Spectrogram until you complete assembly. The defaults given in the manual should be adequate to enable you to get the K2 on the air and to begin playing with it... and this is good, as it allows you to get a 'feel' for the rig and the controls before you get down to the real 'business' of doing the final filter alignment. >Are there any other sections, other than "BFO Alignment" on page 60, where >the use of Spectrogram is recommended? None officially published, but there are a couple different articles available from the Builder's Resource page on the Elecraft site. Go to: http://www.elecraft.com/Apps/new_fil_docs/k2_cw_gram.pdf or http://www.elecraft.com/Apps/new_fil_docs/k2_ssb_gram.pdf depending upon whether you wish to align the CW or the SSB filters. >Your helpful comments are greatly appreciated. I want to do this right the >first time! NOTE that if you will be installing the SSB option board, you are strongly urged to also perform the 2nd Xfil SSB mod which is described at: http://www.elecraft.com/Apps/new_fil_docs/k2_2nd_xfil_ssb_mod.pdf This is a VERY SIMPLE mod and uses one resistor (3.3k to 3.9k), two capacitors (.01uF and 120pF), and a generic small signal PNP transistor (PN2222, 2N3904, 2N4124, etc.). The instructions are step-by-step and include photos. 73 - Tom Hammond N0SS +++++++++++++++++++++++++++++++++++++++++++++++++++ Steve Jackson wrote: > Turns out the > reason no one was answering my calls was that I had a transmit offset (no, > my XIT wasn't on) of about - 1 kHz. > > So, I turned on the XIT control, and adjusted it for +1 kHz or so. Once I > did that, I got every station I called, first time. Perfect, as usual, 5W. > > I am really at a loss to understand what is going on here. Any ideas? > > 73 Steve KZ1X/4 +++++++++++++++++++++++++++++++++++++++++++++++++++ From: Wayne Burdick To: "Randy Moore" I had a talk with Eric about your problem. I misunderstood your situation: I thought you were using the spectrogram program to plot the center frequency of the *noise* output of the RX--I didn't realize you were using a carrier and tracking its pitch, which the K2 will preserve regardless of how you move the BFO! I can assure you that what you're experiencing is not related to the firmware rev., by the way. An example may help: - - VFO dial 7000.0 - - XFIL 4913.6 (center of xtal filter at present bandwidth) - - Sig gen 7000.0 - - BFO 4913.1 - - Sidetone 0.6 - - VCO 11913.7 (VFO + BFO + sidetone) The signal generator's carrier is not quite centered in the filter passband with the present setup -- it's 100 Hz too high: 11913.7 - 7000.0 = 4913.7 = IF carrier freq. But you'll hear the signal at a 600 Hz pitch because that's where you have the sidetone set (BFO - IF): abs( 4913.1 - 4913.7 ) = 0.6 kHz What happens when you run CAL PLL and move the CW-N BFO down 100 Hz to 4913.0? The new VCO value is calculated as soon as you switch filters or modes (in your case, you moved from CW-N to CW-R, then back again): VCO = 7000 + 4913.0 + 0.6 = 11913.6 The IF carrier signal now *is* centered in the filter passband, which is the desired result: 11913.6 - 7000.0 = 4913.6 = new IF carrier freq. BUT, you still hear it at 600 Hz: abs( 4913.0 - 4913.6 ) = 0.6 khz So what we've done is to move the signal in relation to the filter, while *preserving* pitch. (This is similar to IF shift on other radios.) No matter how far you move the BFO, this will always be the case. Hence your spectrogram program will think the signal has not moved--although it *will* be better centered in the crystal filter passband, at least if you've correctly determined what the center frequency of the filter is. You can now move your signal generator or the K2's VFO around a bit to check if the filter center corresponds to the desired pitch. Actually, if you can find the filter center frequency at each bandwidth used (using the "zero-pitch" method), you can then just set the CW-N and CW-R BFOs directly to Fcenter - sidetone and Fcenter + sidetone. That's why we added the BFO DISPLAY mode to CAL FIL. HOWEVER, the bigger problems are still (1) the counter's quantization error, and (2) a small amount of drift with temperature. No matter how much you tweak the BFO, you'll potentially always be off by as much as the sum of these two. I hope this helps! You can see why we don't try to explain this in *too* much detail in the manual. 73, Wayne +++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 25 Jun 2000 14:45:48 EDT From: "ron kerlin" Subject: [Elecraft] spectrograph tip Hello to all in the group. Having just finished (belatedly) sn717, I spent a bit of time playing with the Spectrograph program. The following is a tip that further refines Tom's (N0SS) fine explanation and technique for using this program. It makes available to you a fine marker generator that is built into the K2, and gives a very bright, fine marker that you can very easily see in the sweep bands depicted by Tom's method. It takes no more than 5 minutes to align all 4 filters, both cw normal and cw reverse. Steps are as follows: 1. Select your desired sidetone pitch from the K2 menu. 2. Set up Spectrograph as per Tom's instructions in the Builders Forum. 3. Unhook your antenna, and tune the 7.000 mhz birdie. Use of the preamp is helpful. 4. Using SPOT, carefully zerobeat the birdie. 5. Start Spectro...Set the new index, (under FILE) as per Tom's description, then clik on POINTERS, and set your sidetone pitch in the box provided for the frequency marker. 6. Select MENU/CAL/FILTER/BAND- on your K2 6. Begin Spectrograph, using a low volume setting. 7. You will see a very bright line going thru the depicted bandwidth display. Simply superimpose the marker line on this bright line, then select the next filter. After setting all 4 filters, exit the Cal menu. Repeat for CW rev. You will find that all pitches in both cw nor and cw rev are exactly the same if you zero beat with SPOT. The pitch is within the 10hz tracking tolerance of the sidetone pitch and the cw offset, as explained in the manual. I hope this is of benefit to those of you who are using Spectrograph. It is much faster to set all the filters than to explain!!! Again, thanks to Tom (N0SS) for the use of his Spectrograph setup technique. 73 de Ron/KB9LSH K2 SN717 +++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 4 Mar 2001 20:14:47 EST From: LHLOUSEK at aol.com Subject: Re: [Elecraft] Still stumped with K2 filter alignment Hi Ken, For the receive frequency to be calibrated the following this equation must hold: abs {abs [VFO-VCO] - BFO} = Spot Where VFO is the desired receive frequency, VCO is the frequency of the voltage controlled oscillator, BFO is the frequency of the beat frequency oscillator, and SPOT is the side tone frequency. The lower edge of the xtal filer is fixed in frequency at the IF. In order to move the audio image of the filter you need to change the BFO frequency which is what you do in CAL FIL when you change the BFO parameter. When you exit that menu or go to the next filter the K2 measures the BFO and stores that data so that it can appropriately adjust the VCO so that the above equation is maintained. Due to the frequency measurement resolution and frequency setting resolution differences of +/-20 Hz between settings is common. One of the best ways to get minimal tone shift when switching through the filters is to have the K2 measure each BFO setting in quick succession with the covers on and the unit warmed up. Install the freq cntr probe in TP2, button up the unit and let it warm up 1/2 hr (more on this in another email). Set all your filters using spectrogram the way you normally would. Tune in WWV at 10 MHz so you can hear the beat with the fundamental and step through the filters. If there is significant change it pitch from filter to filter do the following. In CAL FIL hit the BAND - button to get into the BFO parameter setting screen. Change the BFO parameter in that filter by 1 and then back and then hit the FIL button to move to the next filter. (Changing the BFO parameter and switching out of that filter forces the K2 to remeasure the BFO.) Continue through all 4 filters. When done, step through the filters listening the WWV beat. It should be much better. If not try it again. You can do this for all 4 sets of filters (CW, CW rev, USSB, LSSB). I've done this a number of times on my K2 and one belonging to a friend and it has always gotten the beats to agree to within less the 10 Hz between all filters. Luigi +++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 04 Mar 2001 18:16:01 -0700 From: "James E. Fuller" Subject: RE: [Elecraft] re: K2 filter alignment At 05:40 PM 3/4/01, Ken Lotts wrote: >I do not know for absolute sure how I solved this but the problem went away. > >One thing that could have been afoot here was an error in my PLL >calibration. I neglected to put the filter to CW FL1 prior to running PLL >calibration.. I recalibrated all the bands and twiddled my original filter >values back in and things straightened up.. When I got everything together and ready to align things "for good', I just stepped through the procedures in the manual, starting with the 4 MHz reference calibration using WWV at 10 MHz, which took several iterations. Then I went through the CAL PLL procedure on each band in turn, and perturbed the BFO parameter settings on each band as described. Then I went through the CAL FIL procedure for each filter, SSB and CW, using Spectrogram. I followed the manual's procedure, setting the BFO frequency rather than the BFO "parameter". All of this took a while, but it worked. Now I can turn the radio on 10000.00 and my old buddy and/or his girlfriend are right there telling me that "at the tone, the time will be...", when I dial in the W1AW code practice frequencies, they are right there, within 10 Hz, and when I switch from filter to filter on CW, the tone doesn't change at all from FL2 through FL4, and only a max of 10 Hz for any filter, normal or reverse (I'm not entirely sure that it changes 10 Hz, because my ear isn't that good, and I can't read the Spectrogram display that closely (and that is at the limits of its resolution)). I can't claim any magic technique or anything, I just followed the steps systematically and carefully. I'm really happy with it, and I'm really impressed with the stability. Jim Fuller ++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 21 Mar 2001 08:55:44 -0500 From: "Don Wilhelm" Subject: Re: [Elecraft] Question about K2 filter tuning... Ed and all, My experience with very wide filter settings was similar to yours - and was revealed by Spectogram as having a LOT of passband ripple. In fact, with settings on my field test K2 wider than 1.7 bandwidth, I found a spur would develop on the high frequency end which made SSB tuning quite difficult, particularly in USB. The variable crystal filter was designed for narrow passbands (CW), and therefore is a compromise for the wider bandwidths. My suggestion is to set the filter width to something narrower than would be normal for a SSB filter and try again. I find my filter settings of 1.3, 1.5 and 1.7 (plus OPT) to be usable for SSB reception. 73, Don Wilhelm -Chapel Hill, NC W3FPR home page: http://www.w3fpr.webprovider.com QRP-L # 485 K2 SN 0020 mailto: w3fpr at arrl.net +++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 21 Mar 2001 08:31:24 -0800 From: Eric Swartz WA6HHQ - Elecraft Subject: [Re: [Elecraft] Question about K2 filter tuning...] Hi Ed, If you were displaying something different than OP1 in the #1 position you were not using the SSB filter. You were using the variable CW filter in a wide setting which is not optimized for SSB. That is why you heard the difference in audio. While the CW filter can be widened above 1 kHz for casual SSB monitoring it does not compare in SSB RX quality to the fixed OP1 filter on the SSB board. It is optimized for CW use. 73, Eric Ed Juge wrote: > > At one time, I had changed the #1 OPT filter to show 2.4 bandwidth. The > audio sounded terrible... very tinney, no matter where I set the BFO. When > I turned it back to OPT, it sounded good again. Is this normal? Can anyone > tell me why this happens? > > Thanks... Ed, W5EJ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 1 Apr 2001 19:38:30 -0600 From: Kevin Ferguson Subject: [Elecraft] K2 filter/BFO setup clarification needed. The filter setup explaination in the manual (so yes, I RTFM) has left me with a couple of questions: I am unclear why it makes a difference which edge of the passband moves when the bandwidth is changed. it seems to me that the recieved station should be nominally centered within the passband in all cases, and if the edges do not move symetrically, then the BFO needs to be shifted regardless....no? The manual shows how the BFO is shifted to so as to keep a signal at the center of the pass band when the filter bandwidth is changed. This would seem to change the pitch of the recieved signal. (Am I missing something here?) Now when I hit the "spot" function, the sidetone oscillator runs at the same pitch for all filters. So am I really still zero-beating the recieved signal??? If the BFO signal is kept the same in TX mode for all filters, then the answer is yes, but then to zero-beat the station, I must tune him off from the peak of the selected filter. Yes, I can then switch RIT on ( or go to split mode) and re-peak him for best s/n, but that seems like a lot of monkey motion. It seems to me that the LO (VFO per K2 manual) needs to be shifted by the same (or the opposite, depending on band) amount as the BFO so that: 1) the recieved signal stays at the same pitch regardless of filter setting. 2) Using the spot function still results in zero-beat. This would be helpful in crowded conditions, (when you'd be likely to be clamping down the bandwidth) so that the desired signal is not lost when the pitch of all stations changes. This seems to be an "I'm the only one sane" complaint, so I must be missing something here....so please enlighten me. Kevin ko0b (king of zero beaters ++++++++++++++++++++++++++++++++++++++++ Date: Sun, 1 Apr 2001 21:57:45 EDT From: LHLOUSEK at aol.com Subject: Re: [Elecraft] K2 filter/BFO setup clarification needed. Hi Kevin, <<>> The manual isn't very clear either. The trick is in what the MCU does to compensate for changes if the BFO frequency. If the sig is centered in the pass band and you move one edge the sig is no longer centered. To move the sig to the center the VCO must change so that it shifts the IF to the new center frequency. The BFO also shifts to compensate so that the side tone is correct for the RX offset. This sorta happens in reverse when you set the filters up in CAL FIL. When you change the BFO frequency in CAL FIL to move the center of the filter, the MCU reads the new BFO frequency (when you go out of that screen or change filter selection) and subsequently adjusts the VCO so that the VFO reads correctly. The BFO and VCO change in unison to keep the VFO indicating correctly whenever you change filters and/or modes. Luigi +++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 2 Apr 2001 19:47:43 -0400 From: "Francis Belliveau" Subject: Re: [Elecraft] K2 filter/BFO setup clarification needed. On: Sunday, April 01, 2001 9:38 PM "Kevin Ferguson" wrote: > The filter setup explaination in the manual (so yes, I RTFM) has left me with a couple of questions: > > I am unclear why it makes a difference which edge of the passband moves... > ... > It seems to me that the LO (VFO per K2 manual) needs to be shifted by the same (or the opposite, depending on band) amount as the BFO so that: > > 1) the recieved signal stays at the same pitch regardless of filter setting. > > 2) Using the spot function still results in zero-beat. This would be helpful in crowded conditions, (when you'd be likely to be clamping down the bandwidth) so that the desired signal is not lost when the pitch of all stations changes. > Kevin, You are correct that when you have the CW filters set up correctly the received signal will not shift as you change filters. Getting them aligned to accomplish this is not too difficult but describing how presents some difficulty. It is obvious that this is more important to some than others. The procedure that I used was a minor variation of one written by Tom Hammond, N0SS. That procedure can be found at http://www.elecraft.com/Apps/new_fil_docs/N0SS_Filter_Adjustment.html Rather than using a source of audio and zero beating, I used a frequency counter connected to the speaker and measured the side tone frequency then matched it as best I could. There is a small amount of quantization error that I then calibrated out by shifting the filters by one setting to get them to line up as close as possible. Worked out just fine for me. Good Luck, Fran, KA4FRH K2 s/n 314 +++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 13 Apr 2001 17:08:01 -0700 From: "Ron D'Eau Claire" Subject: RE: [Elecraft] K2 and reverse CW Dave, G4AON, wrote: "I have now set the BFO to give the "correct" beat note (750 Hz in my case) for all bandwidths but can't get CW reverse to work as well as I'd like. I tried to match the beat note to 750 Hz using a crystal oscillator for a signal, all looked well on Spectrogram but there is a shift in frequency and a drop in signal level when switching from CW normal to CW reverse on all bandwidths when trying the rig "on air". Is this just my K2, or is CW reverse poor on all K2's?" "Reverse CW" works just fine on my K2, Dave. However, I have never had any luck adjusting the filters listening to anything but noise. Trying to tune them on a 'tone' simply causes the K2 to move the BFO and LO frequencies around "fighting" the changes I am making. Indeed, it is very easy to suddenly discover that you have the BFO clear on the wrong side of zero beat - tuning the wrong sideband! I used Spectrogram to center the BFO frequency (indicated by the marker being set on that frequency in Spectrogram) in the passband on each filter listening to plain ordinary old band noise and it works fine - once the BFO frequencies are measured correctly by the DAC's. I have noticed that it sometimes takes several tries storing the value to get them right. Once I have them set up with spectrogram, if the tone a signal in the passband produces shifts when I step through the filters (including switching from CW normal to CW reverse) I go back to CAL FLTR and change the setting for the BFO, then put it right back to the original setting again. This causes the DAC to re-read the value for the BFO frequency. It's the same sort of thing you do after doing the CAL PLL adjustment to force the K2 to re-read all the BFO frequencies and store new values in memory. After a couple of tries, it has always gotten it 'right' on my K2. My thanks to Luigi, W7DZN for noticing how that works and posting it here some time back! Keep in mind that a 20 or 30 Hz shift is 'normal', owing to the limits on how accurately the DAC can measure the BFO frequency but that's a pretty small shift. Ron AC7AC K2 # 1289 ++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 28 May 2001 19:29:29 -0700 From: "John Grebenkemper, KI6WX" Subject: [Elecraft] Setting Audio Levels in Spectrogram Recently a number of folks on the reflector have been using Spectrogram to make measurements of the K2's filter response. If the audio input level is set too high, clipping will occur in the sound card which will create intermodulation distortion and incorrect readings from Spectrogram. This problem is particularly apparent when measuring broadband noise which is done when making filter response measurements of the K2 filters. For making filter measurements, Spectrogram should be set to 11K Sampling Rate, 16 bit, Mono, and 512 FFT. You can set the other parameters where you want, but I would recommend using the 90 dB dynamic range since it will provide valid measurements as long as you don't overdrive the audio input. For some reason, v6.0.9 displays levels that are 10 dB less than v5.1.6 for the same audio input signal. All measurements given below are for v5; v6 users should set the following guidelines 10 dB lower. When making measurements with the SSB filter, intermodulation distortion will occur when the noise level exceeds -35 dB on the Spectrogram scale.. To leave some headroom, I would recommend taking these measurements with a maximum level of -40 dB. The narrower CW filters with a bandwidth <1kHz provide less noise power so one can measure to higher levels without clipping. These filters start to show intermodulation distortion when the Spectrogram level exceeds -30 dB. Again to provide some headroom, the audio level should be set so that the narrow CW filters do not exceed -35 dB in Spectrogram. A pure tone can be measured to somewhat higher levels in Spectrogram. One measurement I made showed that an over the air carrier received by the K2 started to show intermodulation distortion when the level approached -20 dB on the Spectrogram scale. Any sort of complex modulation would show intermodulation distortion at lower levels. To be absolutely safe, the Spectrogram levels for noise can be followed and you will be guaranteed not to have intermodulation distortion problems in the Spectrogram measurements. In summary, if you use Spectrogram to make K2 filter measurements, make sure that the displayed signal level in Spectrogram does not exceed -35 dB (-45 dB for version 6) for filter bandwidths less than 1 kHz and -40 dB (-50 dB for version 6) for bandwidths wider than 1 kHz. - -John KI6WX +++++++++++++++++++++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: "Greg Fischer" , Subject: Re: [Elecraft] FILTER QUESTION Date: Tue, 8 Jan 2002 23:09:07 -0500 Greg, I can only give you an indirect answer to your question, hopefully you can determine where you want to set Spectogram's frequency markers to aid you in that process. In fact, part of the answer will depend on the hardware you are using to decode rtty/psk. If you are using the familiar computer driven software programs, it may be adequate to simply use the OP1 filter set as you would for normal SSB. If you want better S/N performance and are willing to accept that you will have to do a bit more receiver tuning as opposed to just clicking the audio tone bar on the computer screen, you can follow the steps outlined below. For RTTY, the audio tones to be decoded are 1445 and 1275 Hz for 170 Hz shift RTTY. So you want the passband to be enough greater than 170 Hz so tuning the receiver onto the signal will be not critical (I would suggest 400 to 500 Hz bandpass width). Then you would set the BFO so that both the 1275 Hz and 1445 Hz audio tones are well within the passband as viewed on Spectogram. For PSK31, the procedure is similar, but most folks simply use the normal SSB filter and let the software and soundcard do the audio filtering. You can use a more narrow filter setting to achieve a better S/N ratio, and if you chose to do that, just decide how narrow a bandpass you wish to work with and at what audio frequencies and follow the same procedure as for RTTY above. If I were to make those choices for PSK, I would create a passband from about 800 Hz to 1200 Hz (400 Hz) - but that is just my personal choice - you can pick anything between about 300 Hz and 2700 Hz and accomplish the same thing. Good luck with it, 73, Don Wilhelm - Wake Forest, NC W3FPR home page: http://www.qsl.net/w3fpr/ QRP-L # 485 K2 SN 0020 mailto: w3fpr at arrl.net ----- Original Message ----- > Hi K2ers. I downloaded spectogram and want to set the filters for the > rtty/psk mode (mode r) mode r LSB for rtty and R USB for PSK. Where do I > set the two frequency markers so I can set the noise background properly. I > know (think) they should be different for both rtty and psk31. > ++++++++++++++++++