[Elecraft] K2 freq stability
Agreed, though on my most recent K2, it was close enough to actually change the BFO freq slightly even after releasing the pressure of my hand on the cover, etc., when I picked it up and moved it around. Course we're talking, like, fractions of a millimeter almost lol. I think just the small warp in the RF board and maybe in the bottom cover are just enough to get the panel close enough to the toroid and BFO area to make this happen on my recent K2. I was extremely careful with the bumper and positioning of the resistor and it was still mechanically too close to the panel (I could see the slight divet in the electrical tape when I'd take the cover off, but I never saw that on my first K2). But even K2 #1 pulls the BFO a little when I handle it pressing on the bottom cover with the rig on. Just not nearly as bad as #2 But just the thickness of a lockwasher was enough to spread things out for a great improvement... Definitely not a "problem" problem, but, er,...How about a "very very close tolerance mechanical issue with L33 and the bottom cover", I'll put it that way lol. 73, LS W5QD -- View this message in context: http://elecraft.365791.n2.nabble.com/K2-freq-stability-tp7616601p7616620.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2 freq stability
LS, That is not usually a problem if the rubber mounting stem has been cut off as instructed and the 1/8 watt resistor is pushed down inside the toroid core (so the core cannot move). One does not usually manipulate the bottom cover during operation, so the only time the BFO is liable to shift is when pressure is placed on the bottom cover. That is not 'drift' IMHO, but a change because of the physical proximity of the bottom cover. 73, Don W3FPR On 4/24/2016 9:31 AM, lstavenhagen wrote: Hi all, Here's an interesting finding, though I apologize if this is already in the past archives. No matter how careful you are when installing L33 on the bottom of the board, it's so close to the bottom cover that any movement of it, say when you're picking up the rig or manipulating the bale, etc., will pull the BFO. On my 2nd K2 that I just completed it was so bad that I could pick up the rig, set it back down and the tone of signals was very slightly, but noticeably off. So what I did was put a lockwasher between the cover and the standoff near L33 to raise the cover a little bit and get it the heck away from L33 as much as I could. It actually made a large improvement in the general frequency stability of the rig - which means before I was seeing more contributions in overall drift from the BFO in addition to the rest of the circuitry. The washer is an ugly fix, since the cover bows out a little bit, but it's totally non-destructive and reversible. I did the same fix to my other K2 which didn't have the problem to the same degree, but it helped on that one too. Fortunately the slightly bowed out bottom cover is under the rig and you never see it. But just in case you've been experiencing more drift in your K2 than you think you should get, or it pulls when you pick it up that's a fix that is working on mine. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] K2 freq stability
Hi all, Here's an interesting finding, though I apologize if this is already in the past archives. No matter how careful you are when installing L33 on the bottom of the board, it's so close to the bottom cover that any movement of it, say when you're picking up the rig or manipulating the bale, etc., will pull the BFO. On my 2nd K2 that I just completed it was so bad that I could pick up the rig, set it back down and the tone of signals was very slightly, but noticeably off. So what I did was put a lockwasher between the cover and the standoff near L33 to raise the cover a little bit and get it the heck away from L33 as much as I could. It actually made a large improvement in the general frequency stability of the rig - which means before I was seeing more contributions in overall drift from the BFO in addition to the rest of the circuitry. The washer is an ugly fix, since the cover bows out a little bit, but it's totally non-destructive and reversible. I did the same fix to my other K2 which didn't have the problem to the same degree, but it helped on that one too. Fortunately the slightly bowed out bottom cover is under the rig and you never see it. But just in case you've been experiencing more drift in your K2 than you think you should get, or it pulls when you pick it up that's a fix that is working on mine. 73, LS W5QD -- View this message in context: http://elecraft.365791.n2.nabble.com/K2-freq-stability-tp7616601.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2 Freq. Stability
Thanks to all who helped me work out this problem. I replaced all the BFO components (thanks to Elecraft for sending me the parts at no charge). Now from a cold start at 16C to steady operating temp at 20C, the K2 drifts about 50Hz, well withing spec. In the end, I think the problem was with L33. My original L33 was not wound as carefully as the replacement, and had a couple fewer turns. But who knows. Interestingly, when I reassembled all the BFO components, the K2 did not pass the BFO range test. I reflowed solder, removed L33 and examined it closely, put L33 back in... tried various things to no avail. But then, something I did solved the problem and the oscillator worked fine. Gremlins (or poor soldering). Hope it doesn't revert back to its failed state. Anyway, thanks to all who replied. And, for the record, a properly assembled K2 starting at 16C running up to 20C still meets the published drift specs. I struggled with this problem for quite a while, spent *a lot* of time working it out, and will admit to becoming more than a little frustrated and disillusioned with my K2. But my experience epitomizes the difference between buying and running a stock radio, and building and trouble shooting your own work. If all you want to do is work stations, a K2 is probably not for you; if you enjoy radio more broadly, then the K2 is ideal. Cheers, Doug K8EXB -Original Message- From: w3...@embarqmail.com Sent: Wed, 20 Jan 2010 08:58:47 -0500 To: d...@inbox.com Subject: Re: [Elecraft] K2 Freq. Stability Doug, The BFO is obviously the culprit here. What serial number is this K2? Do you have the new L33? with many turns of #36 wire. If this is an older K2, install the BFO upgrade kit. If you already have the upgraded parts, then I suggest you equip yourself with all of the parts in the BFO circuit and just replace them. You can replace them one at a time until you find things more stable, but I believe it is easier to replace them wholesale and see what happens. You will need 2 BFO crystals X3 and X4 C173 and C174 D37 and D38 L33 Replacing L33 will require a high value 1/8 watt resistor to mount the toroid - the K2 lists this as R116 PN E500086. 73, Don W3FPR Douglas Furton wrote: Hello, all I've been bothered with the CW tone/filter setting on my K2 for some time now. I seem to need to run CAL FIL daily, at least to have the BFO freq. read into memory. I observe that the CW tone starts low and drifts upwards as the rig warms up when I tune a signal to the center of the filters (maxing the S-meter). Here is some data characterizing the freq. drift in my K2 (#6761). I measured the PLL and BFO freqs with a nice frequency counter. I measured these shifts with the K2 locked at 7050 kHz, and computed the total shift = dPLL - dBFO (all referred back to the initial (T=18.5C) measurements. I measured the temp. with a thermocouple in contact with the PLL thermistor board. I also measured the PLL and BFO control voltages at various times and found them to be constant. Cumulative freq. Shifts TPLL BFO Total (C) (Hz)(Hz)(Hz) 18.5 0 0 0 19.3 9 -17 26 19.6 13 -34 47 20.2 17 -57 74 20.8 19 -70 89 21.3 24 -79 103 21.6 26 -87 113 22.0 28 -92 120 23.3 37 -124161 24.0 40 -136176 24.5 46 -164210 25.0 53 -205258 25.5 62 -256318 25.5 70 -310380 (I hope the table above remains tabulated properly. Best viewed with a monospace font.) It seems the thermistor board compensates the PLL fairly well (although maybe I could tweak RA upwards a bit), but the BFO drifts considerably, and since the PLL and BFO drift in opposite directions, the total drift is exaggerated. I may measure the drift on a second band, but these data are just from 40 m. I would really like to improve the temp. stability of my K2. Does anyone have any suggestions? Thanks, Doug Furton K8EXB GET FREE 5GB EMAIL - Check out spam free email with many cool features! Visit http://www.inbox.com/email to find out more! __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 02:34:00 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo
[Elecraft] K2 Freq. Stability
Hello, all I've been bothered with the CW tone/filter setting on my K2 for some time now. I seem to need to run CAL FIL daily, at least to have the BFO freq. read into memory. I observe that the CW tone starts low and drifts upwards as the rig warms up when I tune a signal to the center of the filters (maxing the S-meter). Here is some data characterizing the freq. drift in my K2 (#6761). I measured the PLL and BFO freqs with a nice frequency counter. I measured these shifts with the K2 locked at 7050 kHz, and computed the total shift = dPLL - dBFO (all referred back to the initial (T=18.5C) measurements. I measured the temp. with a thermocouple in contact with the PLL thermistor board. I also measured the PLL and BFO control voltages at various times and found them to be constant. Cumulative freq. Shifts T PLL BFO Total (C) (Hz)(Hz)(Hz) 18.50 0 0 19.39 -17 26 19.613 -34 47 20.217 -57 74 20.819 -70 89 21.324 -79 103 21.626 -87 113 22.028 -92 120 23.337 -124161 24.040 -136176 24.546 -164210 25.053 -205258 25.562 -256318 25.570 -310380 (I hope the table above remains tabulated properly. Best viewed with a monospace font.) It seems the thermistor board compensates the PLL fairly well (although maybe I could tweak RA upwards a bit), but the BFO drifts considerably, and since the PLL and BFO drift in opposite directions, the total drift is exaggerated. I may measure the drift on a second band, but these data are just from 40 m. I would really like to improve the temp. stability of my K2. Does anyone have any suggestions? Thanks, Doug Furton K8EXB GET FREE 5GB EMAIL - Check out spam free email with many cool features! Visit http://www.inbox.com/email to find out more! __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] K2 Freq. Stability
Doug, The BFO is obviously the culprit here. What serial number is this K2? Do you have the new L33? with many turns of #36 wire. If this is an older K2, install the BFO upgrade kit. If you already have the upgraded parts, then I suggest you equip yourself with all of the parts in the BFO circuit and just replace them. You can replace them one at a time until you find things more stable, but I believe it is easier to replace them wholesale and see what happens. You will need 2 BFO crystals X3 and X4 C173 and C174 D37 and D38 L33 Replacing L33 will require a high value 1/8 watt resistor to mount the toroid - the K2 lists this as R116 PN E500086. 73, Don W3FPR Douglas Furton wrote: Hello, all I've been bothered with the CW tone/filter setting on my K2 for some time now. I seem to need to run CAL FIL daily, at least to have the BFO freq. read into memory. I observe that the CW tone starts low and drifts upwards as the rig warms up when I tune a signal to the center of the filters (maxing the S-meter). Here is some data characterizing the freq. drift in my K2 (#6761). I measured the PLL and BFO freqs with a nice frequency counter. I measured these shifts with the K2 locked at 7050 kHz, and computed the total shift = dPLL - dBFO (all referred back to the initial (T=18.5C) measurements. I measured the temp. with a thermocouple in contact with the PLL thermistor board. I also measured the PLL and BFO control voltages at various times and found them to be constant. Cumulative freq. Shifts T PLL BFO Total (C) (Hz)(Hz)(Hz) 18.5 0 0 0 19.3 9 -17 26 19.6 13 -34 47 20.2 17 -57 74 20.8 19 -70 89 21.3 24 -79 103 21.6 26 -87 113 22.0 28 -92 120 23.3 37 -124161 24.0 40 -136176 24.5 46 -164210 25.0 53 -205258 25.5 62 -256318 25.5 70 -310380 (I hope the table above remains tabulated properly. Best viewed with a monospace font.) It seems the thermistor board compensates the PLL fairly well (although maybe I could tweak RA upwards a bit), but the BFO drifts considerably, and since the PLL and BFO drift in opposite directions, the total drift is exaggerated. I may measure the drift on a second band, but these data are just from 40 m. I would really like to improve the temp. stability of my K2. Does anyone have any suggestions? Thanks, Doug Furton K8EXB GET FREE 5GB EMAIL - Check out spam free email with many cool features! Visit http://www.inbox.com/email to find out more! __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 02:34:00 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] K2 Freq. Stability
For a comparison point, you might wish to look at my K2 stability measurements at http://www.cliftonlaboratories.com/k2_freq_stability.htm Jack K8ZOA On 1/20/2010 8:58 AM, Don Wilhelm wrote: Doug, The BFO is obviously the culprit here. What serial number is this K2? Do you have the new L33? with many turns of #36 wire. If this is an older K2, install the BFO upgrade kit. If you already have the upgraded parts, then I suggest you equip yourself with all of the parts in the BFO circuit and just replace them. You can replace them one at a time until you find things more stable, but I believe it is easier to replace them wholesale and see what happens. You will need 2 BFO crystals X3 and X4 C173 and C174 D37 and D38 L33 Replacing L33 will require a high value 1/8 watt resistor to mount the toroid - the K2 lists this as R116 PN E500086. 73, Don W3FPR Douglas Furton wrote: Hello, all I've been bothered with the CW tone/filter setting on my K2 for some time now. I seem to need to run CAL FIL daily, at least to have the BFO freq. read into memory. I observe that the CW tone starts low and drifts upwards as the rig warms up when I tune a signal to the center of the filters (maxing the S-meter). Here is some data characterizing the freq. drift in my K2 (#6761). I measured the PLL and BFO freqs with a nice frequency counter. I measured these shifts with the K2 locked at 7050 kHz, and computed the total shift = dPLL - dBFO (all referred back to the initial (T=18.5C) measurements. I measured the temp. with a thermocouple in contact with the PLL thermistor board. I also measured the PLL and BFO control voltages at various times and found them to be constant. Cumulative freq. Shifts TPLL BFO Total (C) (Hz)(Hz)(Hz) 18.5 0 0 0 19.3 9 -17 26 19.6 13 -34 47 20.2 17 -57 74 20.8 19 -70 89 21.3 24 -79 103 21.6 26 -87 113 22.0 28 -92 120 23.3 37 -124161 24.0 40 -136176 24.5 46 -164210 25.0 53 -205258 25.5 62 -256318 25.5 70 -310380 (I hope the table above remains tabulated properly. Best viewed with a monospace font.) It seems the thermistor board compensates the PLL fairly well (although maybe I could tweak RA upwards a bit), but the BFO drifts considerably, and since the PLL and BFO drift in opposite directions, the total drift is exaggerated. I may measure the drift on a second band, but these data are just from 40 m. I would really like to improve the temp. stability of my K2. Does anyone have any suggestions? Thanks, Doug Furton K8EXB GET FREE 5GB EMAIL - Check out spam free email with many cool features! Visit http://www.inbox.com/email to find out more! __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 02:34:00 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
