Hi again,
As a few people pointed out, I misspoke in my earlier email. When I calibrate C22 I immediately run CAL PLL and CAL FIL. True, the K2 does not directly reference C22 during normal operation. My calibration of C22 and then CAL PLL and CAL FIL is all by-the-book. That being said, I still do notice a temperature-dependent frequency drift during normal usage. The drift is predictable, with the zero beat on the dial I get with reference to WWV drifting by as much as 70-80 Hz if the temperature difference between ambient and the max temp the rig hits with the KPA100 under heavy use is large. The frequency at which I can zero-beat WWV does not change unpredictably. The radio consistently zero-beats low (e.g. WWV zero-beats at 10.000.07) when cold. Is this a really big deal? On SSB, certainly not. On CW I like to zero-beat dead-on with the narrow filters. Perhaps I'm just being a perfectionist. Adam, N1KO _______________________________________________ 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 |
Adam,
You cite 70 to 80 Hz drift from a cold start. That is within the K2 spec of <100 Hz drift typical from a cold start at 25C (77F). If your ambient temperature is lower, you can expect more warm-up drift. Once warmed up, the drift should be small. Even my stable HP6840 takes about 2 hours to stabilize after I power it on, and I have the MIL version, so there is a big sticker on the front warning that it has this warm-up drift. I just refrain from measuring anything until the warm-up drift has subsided - so I contend that even fine lab equipment is subject to warm-up drift and to expect that a K2 would be totally stable from a cold start at ambient temperature is IMHO being unrealistic. I do not know of any ham gear that does not have some warm-up drift unless all the oscillators are contained inside a temperature controlled ovens. Only high-end homebrew transcievers can achive that kind of stability, to manufacture units like that would be too costly for the general ham market. Or did I understand something incorrectly? 73, Don W3FPR > -----Original Message----- > > As a few people pointed out, I misspoke in my earlier email. > > When I calibrate C22 I immediately run CAL PLL and CAL FIL. > True, the K2 does not directly reference C22 during normal > operation. My calibration of C22 and then CAL PLL and CAL > FIL is all by-the-book. > > That being said, I still do notice a temperature-dependent > frequency drift during normal usage. The drift is > predictable, with the zero beat on the dial I get with > reference to WWV drifting by as much as 70-80 Hz if the > temperature difference between ambient and the max temp the > rig hits with the KPA100 under heavy use is large. The > frequency at which I can zero-beat WWV does not change > unpredictably. The radio consistently zero-beats low (e.g. > WWV zero-beats at 10.000.07) when cold. > > Is this a really big deal? On SSB, certainly not. On CW I > like to zero-beat dead-on with the narrow filters. Perhaps > I'm just being a perfectionist. > > Adam, N1KO > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.26/601 - Release Date: 12/24/2006 11:31 AM _______________________________________________ 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 |
In reply to this post by adamkern
Adam, The K2 PLL Ref Upgrade manual gives some information on typical drift i.e. 5 to 20 Hz per 15 degrees F on 20 meters. It also explains how changing RA on the thermistor board can better compensate for the drift. Since your drift is consistent, I think you should be able to reduce it by adjusting RA on the thermistor board. 73 Kevin w9cf >That being said, I still do notice a temperature-dependent >frequency drift during normal usage. The drift is >predictable, with the zero beat on the dial I get with >reference to WWV drifting by as much as 70-80 Hz if the >temperature difference between ambient and the max temp the >rig hits with the KPA100 under heavy use is large. The >frequency at which I can zero-beat WWV does not change >unpredictably. The radio consistently zero-beats low (e.g. >WWV zero-beats at 10.000.07) when cold. >Adam, N1KO _______________________________________________ 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 |
Kevin,
The RA resistor on the thermistor board is intended to compensate for drift AFTER warmup - such as drift that might occur due to the additional heating when the KPA100 is transmitting. I do not believe it would be fruitful to attempt to compensate for the initial warmup drift that one may find in the K2 - and you may wind up overcompensating and find the drift after a warmup period would be greater - it would not be good to have a K2 that does not drift when first turned on and then begins to drift after some warmup period. Or perhaps better said, the thermistor board provides compensation for the PLL reference oscillator. There are many more components involved in the initial warmup drift - the BFO is one. It would be interesting to try, but would take a lot of controlled test conditions to verify the results. 73, Don W3FPR > -----Original Message----- > > The K2 PLL Ref Upgrade manual gives some information on typical drift i.e. > 5 to 20 Hz per 15 degrees F on 20 meters. It also explains how changing RA > on the thermistor board can better compensate for the drift. Since your > drift is consistent, I think you should be able to reduce it by adjusting > RA on the thermistor board. > > 73 Kevin w9cf > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.26/601 - Release Date: 12/24/2006 11:31 AM _______________________________________________ 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 |
I don't really see, or notice, any drift in my K2. I'm sure it does
a bit, but it must be a small amount, and negligible for my purposes Stan Rife W5EWA Houston, TX K2 S/N 4216 -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Don Wilhelm Sent: Sunday, December 24, 2006 2:26 PM To: Kevin Schmidt; [hidden email] Subject: RE: [Elecraft] K2 frequency drift Kevin, The RA resistor on the thermistor board is intended to compensate for drift AFTER warmup - such as drift that might occur due to the additional heating when the KPA100 is transmitting. I do not believe it would be fruitful to attempt to compensate for the initial warmup drift that one may find in the K2 - and you may wind up overcompensating and find the drift after a warmup period would be greater - it would not be good to have a K2 that does not drift when first turned on and then begins to drift after some warmup period. Or perhaps better said, the thermistor board provides compensation for the PLL reference oscillator. There are many more components involved in the initial warmup drift - the BFO is one. It would be interesting to try, but would take a lot of controlled test conditions to verify the results. 73, Don W3FPR > -----Original Message----- > > The K2 PLL Ref Upgrade manual gives some information on typical drift i.e. > 5 to 20 Hz per 15 degrees F on 20 meters. It also explains how changing RA > on the thermistor board can better compensate for the drift. Since your > drift is consistent, I think you should be able to reduce it by adjusting > RA on the thermistor board. > > 73 Kevin w9cf > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.26/601 - Release Date: 12/24/2006 11:31 AM _______________________________________________ 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 |
In reply to this post by Don Wilhelm-3
Don,
I agree about warm up drift. Perhaps I misunderstood Adam, but I thought that his problem was that even during normal usage he found objectionable drift when he operated his KPA100 for a while. I presume, perhaps wrongly, that this is most likely coming from the PLL since I thought that the heating due to the KPA100 was what lead John, KI6WX to come up with the thermistor compensation. 73 Kevin w9cf On Sun, Dec 24, 2006 at 03:26:08PM -0500, Don Wilhelm wrote: > Kevin, > > The RA resistor on the thermistor board is intended to compensate for drift > AFTER warmup - such as drift that might occur due to the additional heating > when the KPA100 is transmitting. I do not believe it would be fruitful to > attempt to compensate for the initial warmup drift that one may find in the > K2 - and you may wind up overcompensating and find the drift after a warmup > period would be greater - it would not be good to have a K2 that does not > drift when first turned on and then begins to drift after some warmup > period. > > Or perhaps better said, the thermistor board provides compensation for the > PLL reference oscillator. There are many more components involved in the > initial warmup drift - the BFO is one. > > It would be interesting to try, but would take a lot of controlled test > conditions to verify the results. > > 73, > Don W3FPR > > > -----Original Message----- > > > > The K2 PLL Ref Upgrade manual gives some information on typical drift i.e. > > 5 to 20 Hz per 15 degrees F on 20 meters. It also explains how changing RA > > on the thermistor board can better compensate for the drift. Since your > > drift is consistent, I think you should be able to reduce it by adjusting > > RA on the thermistor board. > > > > 73 Kevin w9cf > > _______________________________________________ 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 |
In reply to this post by Don Wilhelm-3
On Sunday 24 December 2006 15:26, Don Wilhelm wrote:
> Kevin, > > The RA resistor on the thermistor board is intended to compensate for drift > AFTER warmup In 1978 I bought an Eddystone EA12 from Tom, G3YTO, sadly SK in 1985. It used to keep my bedroom/shack warm - thermal stability, and the glow from the dial lights was comforting. My K2 has been on continuously since June 2005 except for power cuts and the ARRL Field Day when I joined three new friends operating 1E, with my transported K2 for a while powered from a solar panel for extra points. I have the LCD LEDs off most of the time. Short of a rubidium or caesium derived source, keeping the equipment on all the time is a good way to stability. Ian, G4ICV, AB2GR, K2 #4962 - June 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 |
In reply to this post by Don Wilhelm-3
For those interested in evaluating their K2's drift without access to test
equipment, here's a process created by John Grebenkemper, KI6WX, while testing the original PLL active frequency compensation mods back in 2003. This procedure will identify the drift in the PLL reference oscillator separately from the BFO oscillator. That's really handy to know if you think your drift is excessive. Otherwise, you don't know which oscillator is causing the drift. Also, on some bands the drift in the BFO oscillator will cancel the drift in the PLL Reference oscillator. That tends to make the K2 seem as though it's very stable on some bands and not so stable on other bands. You'll need a signal you can receive that is very stable over time. The accuracy of the measurement depends upon this, and we're looking for drifts of a few Hz! A good signal is a standards frequency signal such as WWV in the USA at 10 MHz or CHU in Canada. Step 1: Tune in the on-air signal in CW mode selecting the normal sideband (no bar above the C on the display). Carefully zero beat it using the K2's SPOT function, then note the reading on the K2's frequency display. If you're listening to WWV or some other signal with a steady tone modulation, be careful not to zero beat to the sideband of the tone. If you do, your results will be in error by the amount of the tone frequency unless you zero beat to the same tone later. If using WWV, recommend you wait for a silent period to confirm that you are zero beat to the carrier, which should be producing a tone in the K2's speaker equal to the sidetone frequency you're using. We will call the frequency shown in the K2's frequency display "f1cwn", for "frequency 1, CW normal". Step 2: Switch to CW RV, then re-zero beat the carrier to the SPOT tone. We will call this frequency "f1cwr" for "frequency 2, CW reverse". Step 3: Now you wait until you're ready to take a second set of reading to see how much the K2 has drifted. You can go ahead and have some QSO's or just leave the rig running, whatever you want. When running the drift tests, we transmitted at full power into a dummy load for a period of time to simulate some intensive on-air activity. Step 4: Repeat the above measurements taken in Step 1 and Step 2. Call these measurements "f2cwn" and "f2cwr" for "frequency 2 cw normal" and frequency 2 cw reverse". Step 5: Now we calculate the total drift as follows. Subtract f2cwn from f1cwn. Multiply the result by 1000 since the K2 displays KHz and we want to work in Hertz. Algebraically, this is: Delta (i.e. change in) fcwn = 1000(f2cwn - f1cwn) Delta fcwr = 1000(f2cwr - f2cwr) Step 6: Now we calculate the individual drift that has occurred in the BFO oscillator and the PLL reference oscillator as follows: Delta fpll = (delta fcwn + delta fcwr)/2 Delta fbfo= (delta fcwn - delta fcwr)/2 In my K2 I tested the drift at ambient room temperature, +26C, then operated the rig at 100 watts sending CW from a buffer into a dummy load until the internal temperature reached +42C as measured by a probe mounted inside the closed-up rig. The KPA100's heat sink was too hot to leave my hand on it. The maximum drift I found was less than 50 Hz on any band under those extreme conditions. As they say, your mileage may vary, but that should be typical. If you have an old K2 like mine (S/N 1289) that has never been upgraded, it's a worth while effort if you notice any drift. The PLL reference oscillator stability mods were included in all kits after S/N 3446, according to the information on the Elecraft WEB site. Like most improvements to the K2, Elecraft provides an inexpensive kit of parts and instructions you can use to upgrade your K2. Order E850138, K2 Temperature Compensated PLL Reference Upgrade. If your K2 has a serial number earlier than 3000, you'll also need BFOMDKT, K2 BFO Toroid & PLL Ref Osc Xtal Upgrade. 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 |
In reply to this post by adamkern
The K2 drift mentioned by Adam is about 5 ppm for 10 MHz WWV. This isn't
bad for a non-TCXO oscillator. With TCXO oscillators, you can probably get down to 1 ppm, but it might cost you $50 extra. You can do even better by mounting the oscillator in an oven (OCXO), but it will cost you a penalty in both cost and power consumption. Neither of these options is feasible for the K2 design. Now a few comments about some of the other comments on this thread. The PLL reference is the major source of drift in the K2, especially on the higher frequency bands. If you reduce the PLL reference drift enough, you might find that the BFO drift becomes more significant. You can measure BFO versus PLL reference drift by measuring the frequency on both USB and LSB. The thermistor/resistor network for PLL reference frequency stabilization was designed to compensate both for warmup drift and drift induced by a KPA100. In receive only, the K2 internal temperature will rise about 10F in a half-hour. Running a KPA100 at high power can result in even larger temperature excursions. Adjusting RA can reduce this drift; just follow the instructions in the manual. Finally, the PLL reference frequency stabilization was tested in an temperature chamber from 40F to 120F, and the stabilization works well over this temperature range. In one test, the K2/100 was started cold at 59F for 30 minutes, and then put in transmit at 20 watts CW output for 40 minutes. This increased the internal temperature to 114F. The total VFO drift over this temperature range was 70 Hz; the total BFO drift was 10 Hz. The test unit has an optimized RA resistor. -John KI6WX ----- Original Message ----- From: <[hidden email]> > That being said, I still do notice a temperature-dependent > frequency drift during normal usage. The drift is > predictable, with the zero beat on the dial I get with > reference to WWV drifting by as much as 70-80 Hz if the > temperature difference between ambient and the max temp the > rig hits with the KPA100 under heavy use is large. The > frequency at which I can zero-beat WWV does not change > unpredictably. The radio consistently zero-beats low (e.g. > WWV zero-beats at 10.000.07) when cold. > > Is this a really big deal? On SSB, certainly not. On CW I > like to zero-beat dead-on with the narrow filters. Perhaps > I'm just being a perfectionist. > _______________________________________________ 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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