++++++++++++++++++++++ See also K2 Freq Calibrate_C22 (This file is a continuation) ++++++++++++++++++++++ From: "Don Brown" To: "Mike McCoy" , "Helmut Usbeck" , Subject: Re: [Elecraft] 4 Mhz oscillator Date: Sun, 29 Dec 2002 09:40:27 -0600 Hi You cannot accurately measure the 4.000 MHz oscillator directly with a frequency counter. Most counters have a 1 meg ohm paralleled with about 50 Pf on the input plus the added capacitance of the cable and you may have more than 100 pf in capacitance. This loading will upset the frequency of the oscillator. If you use a X10 probe on the counter the probe capacitance is still around 10-12 pf more than enough to pull the oscillator off frequency (remember C22 is at most 50 pf and paralleling 10 pf makes quite a change). The manual has you measure the 12 MHz reference oscillator with the internal and external counter and adjusting the internal to agree with the external. This will get you much closer but you are still depending on the accuracy of the external counter's timebase. The probe loading is why the manual has you connect both probes at the same time so the frequency shift is the same for both probes. This is why the method is more accurate than simply connecting the probe to C22 I prefer using spectrogram to align the 500 and 600 Hz audio tones broadcasted by WWV so they line up with a 500 and 600 marker on the spectrogram display. Then moving the indicated 12 MHz internal oscillator by the same amount with C22. Then re-run CAL PLL and recheck, after a couple of tries I can put The K2 dead on frequency. WWV is much more accurate than any counter, in fact all counters are calibrated to WWV so why not use the most accurate standard? The beating of the 5th harmonic of the 4.000 MHz oscillator with WWV at 20 MHz is also a good method if you have another radio that will tune 20 MHz and will put the K2 dead on frequency. I have tried both methods but I like the Spectrogram method best because you can do the CAL PLL and filter alignment with the same setup. Don Brown KD5NDB ----- Original Message ----- From: "Mike McCoy" To: "Helmut Usbeck" ; Sent: Sunday, December 29, 2002 8:58 AM Subject: Re: [Elecraft] 4 Mhz oscillator > Yes... After an hour warmup I initially used a HP freq counter to set the > oscillator directly to *exactly* 4 Mhz (measuring right off left side of > C22) and after PLL found the display to be off. I then used the recommended > method of matching the display to the freq counter and it is still off. I'm > 99.44% positive my freq counter is in calibration so I don't know what the > problem is. > > As soon as I can hear WWV on 20Mhz I'm going to try the zero beat method. > > 73, > Mike K5PU +++++++++++++++++ From: "Don Brown" To: "Mike McCoy" , Subject: Re: [Elecraft] 4 Mhz oscillator Date: Sun, 29 Dec 2002 10:21:14 -0600 Hi Here are the instructions I send with my noise generator kits. It explains the Spectrogram method: Using the Noise Generator to Align the K2 If your K2 is not performing up to snuff then get in there and set it up right. It sure makes the operation nice It's not that hard to get everything close to perfect if you will spend a little time with WWV, Spectrogram and your noise generator. This is the method I use to align a K2: The first thing is to make sure the K2 is on frequency you can check that by looking at WWV with Spectrogram looking for the 500 and 600 Hz tones on alternating minutes (you may need to wait a little, the tones are not on all minutes of the hour). Use USB or LSB mode. Set up a marker at 500 and 600 Hertz on the Spectrogram display. When you have the tones on the spectrogram markers, read the VFO frequency and write it down. Connect the frequency probe to TP3 in FCNTR mode and adjust C22 on the control board to change the indicated frequency by the amount needed to make the VFO correct. Here is an example: if the VFO is reading 20 counts high then change the frequency at TP3 20 counts lower (note: the frequency at TP3 will be around 12 MHz not the VFO frequency). Move the counter probe to TP1 and select 40 meters and run CAL PLL. This should put your VFO on frequency. Recheck against WWV and repeat if necessary. Then use Spectrogram and your noise generator to set up your filters. Preset them to the settings in the K2 manual first so you are sure you are on the right side of the band-pass then adjust the filters with Spectrogram to center the band-pass on a marker set at your side-tone frequency. The noise generator connected to the K2 antenna makes it easier to see the band-pass. You may need to do all of the above more than once to get everything right. When setting up sideband move the band-pass so the lowest point on the skirt on the left starts just a little past 0 Hz. Set each filter trying to duplicate that left hand skirt. You may need to adjust the K2 volume control for the best display. If you would like to check out your K2 filters here is a quick way to make sure you have it right. Set the band to 80 meters and set the VFO to 4000.00 select CW mode and FL1. You should hear the MPU 4.00 MHz clock as a 600 Hz tone assuming your side tone is set to 600. If not adjust the VFO a little to zero beat with the spot tone. Now cycle through the filters FL1-FL4. The frequency should not change at all or very little. Now without touching the VFO frequency hold the CW REV button to select CW reverse. Again the tone should not change with the reverse or when cycling through the filters. Now switch to USB mode and change the VFO to 3999.40 and you should hear the same note. Cycle through the filters and it should not change. Change to LSB and set the VFO to 4000.60 and you should hear the same 600 Hz note when cycling the filters. If it will do all of the above then you have got it set as good as it gets. Don Brown, KD5NDB +++++++++++++++++ Date: Sun, 29 Dec 2002 17:32:59 +0000 To: Helmut Usbeck , elecraft at mailman.qth.net From: Steven Gibbs Subject: Re: [Elecraft] VFO calibration At 12:20 29/12/02 -0500, Helmut Usbeck wrote: >I had mine sent to a lab where it was compared to a rubicon >standard. = rubidium ?? ('rubicon' has an altogether different meaning) Helmut, I don't know why there should still be such confusion about setting the 4MHz control board oscillator. Here's a couple of methods which have previously been posted to this reflector. 73, Steve GU3MBS ============================================================== Elecraft K2 Control Board 4MHz Oscillator Adjustment by Steve Gibbs GU3MBS sgibbs at guernsey.net 18 Dec 02 Here are two methods of correctly setting the K2 4MHz clock frequency with greater confidence than the methods suggested in the K2 manual, 'Alignment and Test, Part II'. Neither method needs a 'calibrated external frequency counter' or a 'calibrated short-wave or ham-band receiver'. Method A needs a PC running the Spectrogram program, and requires that assembly of the K2 is complete. Method B needs an oscilloscope and a 1MHz frequency standard. It can be performed at the 'Alignment and Test, Part II' stage, or when assembly of the K2 is complete. ======== METHOD A A1. Set the K2 to USB. Identify and tune (approximately zero-beat the carrier) a standard frequency (WWV) transmission on 10MHz, 15MHZ or 20MHz. Tune the K2 dial about 1kHz lower. On Spectrogram you should see the WWV carrier as a tone of about 1000Hz. Disregard any modulation tones that WWV may also be transmitting. A2. Disconnect the antenna; you should see a weak signal somewhere on Spectrogram - this is the 10th (or 15th, or 20th) harmonic of a 1MHz signal derived by the MCU from its 4MHz clock (you will recall that a similarly-derived 7MHz signal is used in initial 40M alignment). You can verify that you are looking at the right signal by touching the Control Board MCU crystal X2 or its associated C22 trimmer and noting that the frequency on the Spectrogram display changes slightly. If you don't see the MCU signal you can tune the K2 dial up or down a couple of hundred Hz until you locate it. A3. If WWV is coming through strongly there may be enough breakthrough to show WWV's signal also. Use an insulated tuning tool (sorry, but the Elecraft tool is rather poor for this job) to adjust Control Board C22 so that the two signals coincide - final proximity may show a beat which can be reduced to zero. If WWV isn't very strong you won't see its breakthrough signal so you'll have to alternately connect and disconnect the antenna until you have the two signals giving the same frequency on the Spectrogram display. A4. Note that the exact setting of the K2 dial and the exact frequency on the Spectrogram display doesn't matter. The sidetone frequency which you have set doesn't matter either. These are the important features of this method. If you have a KAT2 or a KAT100 you can switch to an unconnected ANT2 instead of disconnecting your antenna. A5. Re-perform CAL-FIL & CAL-PLL. A6. SPOT the WWV carrier in CW-nor and again in CW-rev; in each case the K2 dial should show 10000.00kHz (or 15000.00kHz or 20000.00kHz) probably plus or minus about 20Hz. ======== METHOD B If you have access to a 1MHz frequency standard, here's a way of setting the K2's 4MHz Control Board oscillator with greater certainty than trying to zero-beat with WWV. I used an off-the-air standard derived from the high-accuracy carrier frequency of the BBC's 198kHz LW transmission. You will need a 4MHz bandwidth oscilloscope having a high- sensitivity y-amp (5mV/div worked for me), with an independent trigger input derived from your frequency standard. B1. Temporarily reduce the y-amp sensitivity, connect to the trigger source, and adjust the 'scope's timebase and trigger level to stably display one or two cycles of the 1MHz standard frequency. B2. Connect the probe's ground connection to the Control Board ground point. Move the 'scope probe to the vicinity of X2-C21-C22 on the Control Board, but do not touch anything, just rely on loose capacitive coupling. Switch the 'scope to maximum y-sensitivity, and look for a trace showing pick-up from the 4MHz clock oscillator. B3. Use an insulated trimming tool (sorry, but the Elecraft tool is rather poor here) to carefully adjust C22 so that the scope trace is resolved into a sine wave moving slowly or rapidly either to the left or to the right. Note that four cycles occupy the same time as one cycle of the 1MHz reference oscillator. Careful tuning will result in a near- stationary display when the trimming tool is removed, and the 'scope probe is gradually drawn away. This indicates very close matching of the K2's 4MHz oscillator to four times the standard frequency. (A left or right shift of 4 cycles in one second means the frequencies are matched to one part in a million. Temperature effects will degrade frequency accuracy, so it's probably not worthwhile trying for better than this). B4. If you are still building your K2, continue with 'Alignment and Test, Part II, PLL Reference Oscillator Range Test'. Otherwise, re-perform CAL FIL & CAL PLL. +++++++++++++++++++++ From: "Don Brown" To: "Helmut Usbeck" , Subject: Re: [Elecraft] VFO calibration Date: Sun, 29 Dec 2002 11:47:13 -0600 Hi Actually as some who worked in several calibration labs (Tektronix, GE and several independents) That is exactly what we do. The frequency standard in most cal labs is a special receiver that is phase locked to the WWV carrier. The calibration certificates state that the instrument is traceable to NBS. WWV is part of the NBS so it is the standard all other standards are compared to and even if a lab is using a rubidium or cesium standard they are calibrated against the ones at NBS. The WWV carrier is phase locked to their internal standard and the several standards are compared to each other to maintain the reference. Don Brown KD5NDB ----- Original Message ----- From: "Helmut Usbeck" To: Sent: Sunday, December 29, 2002 11:20 AM Subject: [Elecraft] VFO calibration > > -Someone mentioned that all counters are calibrated against WWV. I don't > know where that urban (or rural) legend came from. If you think that > down at H-P techs are zeroing in counters with an old Grundig tuned to 10 > Mc. you're off. I had mine sent to a lab where it was compared to a rubicon > standard. Which of course is what WWV uses as it's standard. +++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] VFO calibration Date: Sun, 29 Dec 2002 13:14:37 -0800 Helm is quite right about WWV not being the "absolute" standard for frequency and time. All serious measurement system calibration in the USA is traceable to the National Institute of Standards and Technology (NIST). They are responsible for providing the standards against which every sort of measurement that is made in the USA can be compared, including frequency and time. NIST runs station WWV, but WWV is not the most accurate source of frequency and time information. The NIST standards are so good that they are actually degraded by the propagation effects of the radio waves from WWV traveling at essentially the speed of light. MOST signal generators, even very expensive ones, aren't any better than the accuracy of the WWV signal, but it is a lot easier to calibrate them using a "secondary standard" in the shop than it is listening to a signal off of the air. The problem for us Hams is that few of us have a reliable "secondary standard" that is as good as WWV, so we go to the trouble to use the WWV signal whenever possible. The whole business of "measuring" something is a scientific discipline in itself. The process of taking data and understanding what it means goes far beyond putting a probe on a circuit and looking at a readout. NIST publishes a very interesting booklet on the subject that doesn't require a math degree to follow. It's available on-line at: http://ts.nist.gov/ts/htdocs/230/233/calibrations/Publications/exp_meas. pdf. It's not radio-oriented, but covers the subject of how to make measurements and analyze the results, including some simple experiments that can be carried out with home-made equipment to demonstrate the process. An important point that most of us realize intuitively is that the accuracy of the measurement need only be good enough for the task at hand. In the case of aligning the K2, if we set the 4.000 MHz oscillator within a several Hz we will have set it many times more accurately than the K2 design is capable of maintaining. Therefore, any errors we find afterward are a result of trade-offs in the K2 design and not in our alignment methods. In simple words, "It's as good at it gets". Of course, some of us start wondering, "I wonder if it could be better...", but that's a different story. As Helm put it so well, "This rig is a hobby unto itself." It sure can be to those of us who like to tinker. And for those who simply want a rig that works very well "On the Air" day in and day out, it does that too as many ops with "stock" K2's have often testified on this reflector. Ron AC7AC K2 # 1289 -Someone mentioned that all counters are calibrated against WWV. I don't know where that urban (or rural) legend came from. If you think that down at H-P techs are zeroing in counters with an old Grundig tuned to 10 Mc. you're off....-Helm. ++++++++++++++++ Date: Sun, 29 Dec 2002 14:46:01 -0700 To: "Don Brown" , "Helmut Usbeck" , From: Roy Subject: Re: [Elecraft] VFO calibration At 11:47 AM 12/29/02 -0600, Don Brown wrote: >Hi > >Actually as some who worked in several calibration labs (Tektronix, GE and >several independents) >That is exactly what we do. The frequency standard in most cal labs is a >special receiver that is phase locked to the WWV carrier. The calibration >certificates state that the instrument is traceable to NBS. WWV is part of >the NBS so it is the standard all other standards are compared to and even >if a lab is using a rubidium or cesium standard they are calibrated against >the ones at NBS. The WWV carrier is phase locked to their internal standard >and the several standards are compared to each other to maintain the >reference. > >Don Brown >KD5NDB > >----- O > > > > > -Someone mentioned that all counters are calibrated against WWV. I don't > > know where that urban (or rural) legend came from. If you think that > > down at H-P techs are zeroing in counters with an old Grundig tuned to 10 > > Mc. you're off. I had mine sent to a lab where it was compared to a >rubicon > > standard. Which of course is what WWV uses as it's standard. At the NIST lab I work at, we have not used the WWV method for quite a few years now. But it worked fine when we did. Now we sync our cesium to a signal from GPS. Then we sync our rubidiums using the cesium. The GPS is now considered an "absolute standard" . Time marches on! Couldn't resist that one. 73 Roy AB7CE ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Andreas Hofmann'" , Subject: RE: [Elecraft] 4 Mhz Oscillator calibration Date: Wed, 29 Jan 2003 21:27:45 -0800 Andreas wrote: Interesting. You are saying that the reference signals (WWV or what ever) should be close or even inside the amateur bands in order to get reasonable results, aren't you? If I do use the 10 MHz WWV, can I assume that a frequency on 14,100 is almost dead on, even though WWV on 20Mhz is way off? How about using one of the beacon frequencies on 15 m or 20 m instead of using WWV? ------------------------------------------------------------------------ ------------------------ Hi! According to the Elecraft K2 User's Manual (Rev C) , they stated that when using a signal with a known frequency to adjust C22 to make the display read accurately: "Because of the way CAL PLL works, you can only use a signal source that is at one of the lower band edges, e.g. 7000.00 or 10000.00 kHz." I suspect that is because those frequencies are ones most accurately measured by the CAL PLL function. CAL PLL builds a "lookup table" of tuning voltages needed to produce the desired frequencies from the local oscillator and BFO. This table does NOT include EVERY frequency you might tune your K2 to. Frequencies in between the measured ones are interpolated or "estimated" by the firmware, so the frequency display is not as accurate for those. That's my understanding of the issue. ALSO, keep in mind that the firmware has been improved to improve the overall frequency accuracy since that procedure was written. I don't know whether that is as much of an issue today as with earlier firmware. If you want to use an "on air" signal on some other frequency, I'd query the Elecraft folks about it first. Some months back several ops on the reflector here noted that their dial accuracy was vastly improved by setting the 4MHz oscillator as close to 4.0000 MHz as possible. Some of them had well-calibrated highly-stable frequency standards they could use. I didn't, but I have long used WWV at 20 MHz to set the 4MHz clock in my frequency counter, and it seemed a logical way to set the 4MHz clock in my K2. I did so and reported excellent results. I used an external receiver that I have in the shack. I tuned in WWV at 20 MHz in "AM" mode, and arranged a pickup wire so I could hear the 4 MHz oscillator beating with the WWV carrier. The adjustment was very easy. Several ops noted that they did NOT have a second receiver and used the K2 itself. Then I was asked to document the procedure, so I tried it with the K2 and found that it was very easy to adjust C22 for zero beat with one of the sidebands of WWV instead of the carrier. That resulted in the 4 MHz clock being several hundred Hz off frequency. A couple of other ops also noted that they had to "give it several tries" to get it right. The two-step process of using the SPOT tone that I sent you earlier seems to have fixed that ambiguity and still results in a setting as close as the K2's circuits could use. You mentioned that WWV at 20 MHz is "way off". I have noticed that my "dial accuracy" on 20 MHz is not nearly as good as it is in the Ham bands or at 10 or 15 MHz for that matter. So I assumed that the firmware is not as good at estimating the correct control voltage that far outside of a Ham band. Let me share a couple of other points about the "dial accuracy" that bear on this issue. Using a frequency counter to spot check frequencies across the Ham bands, I have found that my K2 is within 20 or 30 Hz of the displayed frequency on all bands at MOST times. Please note that the oscillators in the K2 are NOT temperature-compensated. They DO drift a bit with temperature. They are variable crystal oscillators - VXOs - rather than free-running oscillators. So they are reasonably stable but they still change frequency somewhat when subjected to changing temperatures. And when they move, the displayed frequency is thrown off. That surprises some ops used to fully-synthesized rigs. The K2 is NOT a fully-synthesized rig with the oscillators rigidly "tied" to a master clock oscillator. That gives it some very big advantages in the "cleanness" of the oscillator signals that shows up in everyday use in low noise in the receiver and higher than usual resistance to certain types of interference, but it has the disadvantage that the oscillators may "drift" a bit in frequency. And then you must consider the fact that the hardware in the K2 (the digital to analog converters or "DACs") have a resolution limit too. That resolution limit allows an additional frequency error of 20 or 30 Hz. Note that Elecraft says that the VFO stability is "<100 Hz total drift typ. from cold start at 25 degrees C". Under most conditions, my K2 is well inside that limit. When we talk about "drift" under normal operating conditions, we are talking about values too low for most ops to detect by ear. If there is anything further that I can do, just ask! 73, Ron AC7AC K2 # 1289 ++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'John Huffman'" , "'Elecraft'" Subject: RE: [Elecraft] Freq probe Date: Mon, 3 Mar 2003 12:28:10 -0800 That's an excellent question, John! The issue of putting the cover on to run PLL came up a couple of years ago before the KPA100 was released. The KPA100 might well cause a different shift. I haven't heard from the Ele-guys about it. Maybe Wayne or Eric will chip in. I got in the habit of dropping the top cover in place when running CAL PLL, and so I didn't even think about it. I did that in order to get the best "dial calibration". I was not aware that running CAL PLL could also cause the "5 kHz artifacts" until the recent posts on the subject, but it makes sense since putting the cover on after doing the CAL PLL shifts the oscillator frequency. BTW, a number of posts refer to the instruction to remove the probe before operating the K2 to avoid slightly greater spurious signals in transmit. That's true, but that caution refers specifically to removing the probe from the BFO test point. In the past, we often left the probe in the BFO test point so we could re-run CAL FIL to adjust the filters at any time the mood stuck without opening up the K2 again. I believe the earlier assembly instructions even suggested doing this. But that's not what we are doing here. We are talking about the PLL Reference Oscillator test point for CAL PLL, not the BFO test point for CAL FIL. I don't know what the impact would be, if any, of leaving the probe in the Reference Oscillator test point when operating. I still remove it because things are really crowded in there anyway with the KPA100 lid on it, and I found that the KPA100 squashed the cable down if I left it connected. Ron AC7AC K2 # 1289 -----Original Message----- From: elecraft-admin at mailman.qth.net [mailto:elecraft-admin at mailman.qth.net] On Behalf Of John Huffman Sent: Monday, March 03, 2003 9:45 AM To: rondec at easystreet.com; 'Elecraft' Subject: Re: [Elecraft] Freq probe Ron - Is this also necessary it the top cover is the KPA100? 73 de NA8M John ++++++++++++++++++ From: "glen & sue" To: Date: Wed, 19 Mar 2003 17:24:51 -0500 Subject: [Elecraft] Another K at frequency calibration technique ANOTHER K2 FREQUENCY CALIBRATION TECHNIQUE Glen Worstell, KG0T March 19, 2003 For builders who do not have access to a counter, a marker generator, or another receiver, the manual suggests a frequency calibration technique involving zero-beating the receiver with WWV at 10 MHz. However, tuning to zero beat within a few Hz is very difficult because the response of the receiver falls off drastically at low audio frequencies (as it should). An alternate method is to turn on the sidetone oscillator and tune WWV at 10 MHz so that the WWV carrier is heard at the same frequency as the sidetone. By adjusting the receiver volume (and, if necessary the sidetone volume) so that the two tones are about equal in amplitude it is fairly easy to find the dial setting that is closest to zero beat. Because of the 10 Hz frequency steps the best (lowest) beat frequency may be as much as 5 Hz, which is still very easy to hear. It is best to do this during the short time each minute when the WWV audio tone is off. Because of the way the sidetone is implemented in the K2, the sidetone frequencies are not exactly the values set in the sidetone pitch menu (ST P), but the frequencies are known and are accurate to a fraction of a Hz regardless of the setting of the 4 Mhz reference oscillator frequency (C22). The relationship between the ST P settings and the actual sidetown frequencies is not simple and is not known by the author, but the factory kindly supplied the value for a ST P setting of 0.65. Set the sidetone pitch to 650 Hz (0.65 will be displayed). The actual pitch for this setting is very close to 660 Hz. Tune the receiver to 10000.66 KHz (LSB mode), and you should be able to hear the WWV carrier. Turn on the sidetone and slowly adjust the receiver frequency until you hear the WWV carrier beating with the sidetone. You should be able to hear a very distinct low frequency beat when you are close to the best setting. You are not hearing the actual low frequency note, which will be only a few Hz, but you will hear the tone rise and fall in amplitude at a rate of a few Hz. The frequency of the beat note may be very close to zero, with one beat every few seconds, or it may be off by as much as 5 Hz. You should be able to hear the beat frequency increase if the dial is turned one step CW or CCW from the setting that gives the closest match between the sidetone and the WWV carrier. The procedure outlined in the manual is then followed, except that the vfo difference will be with respect to 10 Mhz PLUS the sidetone frequency of 660 Hz (if using LSB) or MINUS the sidetone frequency (if using USB). Important note: the actual sidetone frequency, as described above, will be about 660 Hz when ST P is set to 650. Be careful not to move the K2 dial during the operation. You might want to leave ST P set to 0.65 and adjust the CW filters and audio filters (if installed) to use this value. By doing so it is then easy to check the calibration without removing the top cover. You can use any of the WWV frequencies or the CHU frequency of 7.335 MHz. This technique is accurate (within the limits of the K2 10 Hz resolution), fast, and easy, and it requires no test equipment. ++++++++++++++++++++++ Date: Wed, 19 Mar 2003 20:34:28 -0800 (PST) From: Leroy Buller Subject: Re: [Elecraft] Another K at frequency calibration technique To: Elecraft Reflector Glen has a good idea. What I've also tried to do with some success use the WWV signal and set up Spectorgram for two markers at 500 Hz and 600 Hz. At sometime in the minute, the two tone come on and you can see them very clearly in the bandpass. I just move the VFO to those two marks...get them as close as possible and you should be on the 10 Mhz dime. Then adjust the rig appropriately. Lee - K0WA ++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Elecraft Reflector'" Subject: RE: [Elecraft] Another K at frequency calibration technique Date: Wed, 19 Mar 2003 20:57:58 -0800 A similar procedure that I've passed on to a number of ops with success = uses the harmonics of the signals derived from the 4. Mhz clock.=20 Tune in WWV at 10 or 20 MHz and zero beat the carrier with the SPOT function, just like tuning in any CW signal as Glen described. Lock the tuning so you won't "bump" it.=20 Replaced the antenna by a test lead and touch the other end to the can = of the 4 MHz oscillator crystal. A loud fifth harmonic of the oscillator = will be heard if the rig is tuned to 20 MHz or a weaker harmonic of one of = the "counted-down" products of the oscillator will be heard if the rig tuned = to WWV at 10 MHz.=20 Check to see that you are hearing the 4 MHz oscillator on the control = board by touching C22 and verifying that the frequency shifts.=20 (If you have the KPA100 operating, it's 4 MHz clock may be interfering = with you. If so adjust it to a higher frequency. Elecraft recommends this to = keep it from interfering with signals at the top of the 75 meter band. The frequency of the 4 MHz clock in the KPA100 is not critical and has no = effect on any calibration).=20 Adjust C22 so the signal is zero beat with the SPOT tone again and you = are done. Of course, CAL PLL must be run again and the system forced to re-read = all of the CAL FIL BFO frequencies before the change takes effect.=20 As Glen points out, you can't get any closer than this. It doesn't = matter if you can't get the 4 MHz oscillator exactly zero beat with the SPOT, = since you are using a harmonic anyway. A 10 Hz at 20 MHz is actually only a 2 = Hz error at 4 MHz, for example.=20 Ron AC7AC K2 # 1289 ++++++++++++++++++++ From: "Wallace, Andy" To: "'rondec at easystreet.com'" , "'Elecraft Reflector'" Subject: RE: [Elecraft] Another K2 frequency calibration technique Date: Thu, 20 Mar 2003 12:37:17 -0500 > -----Original Message----- > From: Ron D'Eau Claire [mailto:rondec at easystreet.com] > > You don't try to find a zero Hz audio beat. The point is to > "zero beat" the SPOT tone - the sidetone - at whatever frequency you > have it set for in CW mode, just like you'd tune in any CW signal. Then you > aren't dealing with the fact that the K2 can't real low audio frequencies. Ah, right you are. I TOLD you my coffee hadn't kicked in... ;-) Well my technique was to zero beat the VFO with the voice announcement of WWV so the (computer) voice sounded normal, then adjusted the trimcap during a quiet period of WWV. My brother has my oscilloscope otherwise I could have used that on the audio line to see if the <10 Hz wave could be seen and not heard. hi Regardless -- your point about the small error at 20 MHz being VERY small at 4 MHz is the best part about the technique, whichever one you use at this frequency. Andy +++++++++++++++++++ From: "Francis Belliveau" To: "'Elecraft Reflector'" Subject: Re: [Elecraft] Another K2 frequency calibration technique Date: Thu, 20 Mar 2003 12:59:51 -0500 Please note that zero beating the carrier in CW mode is much simpler, an less subjective, that trying to zero beat in SSB mode. At least IMHO. As for what to do next, that's up to you. I used Ron's procedure and provided feedback on a proper write-up rather than the abridged version that he provided in the email. What's the test count on this procedure so far Ron? Fran +++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Elecraft Reflector'" Subject: RE: [Elecraft] Another K at frequency calibration technique Date: Thu, 20 Mar 2003 10:16:57 -0800 Right you are Mike... That's always the issue when the rigs get more complex. With every added oscillator is a whole spectrum of harmonics, heterodynes, heterodynes of harmonics, etc.. Ron AC7AC K2 # 1289 -----Original Message----- (If you have the KPA100 operating, it's 4 MHz clock may be interfering = with you. If so adjust it to a higher frequency. Elecraft recommends this to = keep it from interfering with signals at the top of the 75 meter band. The frequency of the 4 MHz clock in the KPA100 is not critical and has no = effect on any calibration). And instead you can interfere with low level signals at the bottom of = the 10 metre band. Take your pick. Regards, Mike VP8NO ++++++++++++++++++