RE: [Elecraft] K2 frequency drift
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: Elecraft@mailman.qth.net 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: [Elecraft] K2 frequency drift
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: Elecraft@mailman.qth.net 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: [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: Elecraft@mailman.qth.net 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: [Elecraft] K2 frequency drift
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: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Don Wilhelm Sent: Sunday, December 24, 2006 2:26 PM To: Kevin Schmidt; elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: [Elecraft] K2 frequency drift
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: Elecraft@mailman.qth.net 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: [Elecraft] K2 frequency drift
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: Elecraft@mailman.qth.net 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: [Elecraft] K2 frequency drift
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: [EMAIL PROTECTED] 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: Elecraft@mailman.qth.net 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: [Elecraft] K2 frequency drift
Dave, It is not abnormal for electronic equipment to have some warm-up drift, the K2 is no excpetion, so I would hesitate to call the situation you describe as a 'problem'. You can download the K2 Temperature-Compensated PLL Reference Upgrade document from the Elecraft website - it contains a procedure for adjusting the ampount of compensation. Do note that even this procedure calls for letting the K2 warm up for 30 minutes before attempting to measure drift. The temperature compensation change is directed toward reducing drift during operating cycles of alternate transmit/receive conditions rather than attacking the warm-up drift, but it may assist with warm-up drift, or maybe not - it all depends. For this reason, you may want to delay making any adjustment until after you have the KPA100 installed because the temperature differential may be different with the KPA100 installed. The KPA100 will not cause any problems, but the temperature swing inside the case will be greater than with the QRP K2. The nominal value for RA works for most environments, but you may wish to experiment a bit and see if your compensation can be improved. The K2 spec is for less than 100 Hz total drift from a cold start (25 degrees C.), so your K2 is operating well within the specs. 73, Don W3FPR -Original Message- Two questions for the group: 1. My K2, serial 5120, has worked flawless since I built it last fall...except that about a week ago, friends on a 20m net I work daily said I was low about 40 Hz in frequency. (Frequency calibration checked occasionally against both my external counter and WWV had been right on.) I transmitted first maybe 2 minutes after turning the rig on. So I dialed up about 40 Hz (.04 kHz) to get on frequency. In the next 15 minutes, I had to move the indicated frequency down slowly to the exact net freq. Drift was the obviously the problem. Since then, I've turned the K2 on early and found that by net time, it was on the exact frequency on the LCD. However, just after turning it on (room temp constand at about 68F), tuning WWV on 10 MHz (equalizing the stations's audio tone on USB and LSB) shows I'm low by 40-50 Hz, drifting up to indicated freq. in 15-20 minutes. I know that resistors RA and RD on the thermister board control drift rate, and some months ago there were comments here on how to compensate, but I didn't retain the thread. Anybody care to provide that advice again or new comments? 2. I'm currently building a KPA100 internal amplifier kit, and I'm wondering if the added heat creates drift or frequency calibration problems. Dave Martin ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] K2 frequency drift
Dave; I designed the K2 VFO stability mod that is now included in all K2's. Variations in the crystal stability cause each K2 to drift slightly differently. That's why I included the instructions on how to adjust the resistor values to minimize the K2's drift. I tested my K2 from 15C to 45C in a home built environmental chamber (use one of those thermoelectric cooler/heaters from WalMart or Target). I picked the resistor values to produce the minimum drift over an assortment of crystals that Elecraft sent me. I also adjusted those resistor values to achieve minimum drift in my K2. Over that temperature range, my K2 shows a maximum drift rate on its worst case band of 15m of 1.8 Hz/C. The average drift rate is less than 1 Hz/C. The K2 warmup internal temperature change is 5C. On 20m, my K2 will show a warmup drift of about 5 Hz. This shows what you can achieve if you run a careful set of experiments with different resistor values. I only know of a few people who have actually adjusted the resistor values. It is a long time consuming process with very careful data measurement. However, you can reduce your drift rate following the printed procedure. -John KI6WX - Original Message - From: [EMAIL PROTECTED] To: Elecraft@mailman.qth.net Sent: Wednesday, March 15, 2006 1:58 PM Subject: [Elecraft] K2 frequency drift Two questions for the group: 1. My K2, serial 5120, has worked flawless since I built it last fall...except that about a week ago, friends on a 20m net I work daily said I was low about 40 Hz in frequency. (Frequency calibration checked occasionally against both my external counter and WWV had been right on.) I transmitted first maybe 2 minutes after turning the rig on. So I dialed up about 40 Hz (.04 kHz) to get on frequency. In the next 15 minutes, I had to move the indicated frequency down slowly to the exact net freq. Drift was the obviously the problem. Since then, I've turned the K2 on early and found that by net time, it was on the exact frequency on the LCD. However, just after turning it on (room temp constand at about 68F), tuning WWV on 10 MHz (equalizing the stations's audio tone on USB and LSB) shows I'm low by 40-50 Hz, drifting up to indicated freq. in 15-20 minutes. I know that resistors RA and RD on the thermister board control drift rate, and some months ago there were comments here on how to compensate, but I didn't retain the thread. Anybody care to provide that advice again or new comments? 2. I'm currently building a KPA100 internal amplifier kit, and I'm wondering if the added heat creates drift or frequency calibration problems. Dave Martin ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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
