Re: [time-nuts] HP 10811 Tuning Diode
I had a noisy varactor experience too: in my Tek 492 one day I noticed an increase in the 0 beat noise and the PLL not working. When I replaced the 2.2GHz conversion varactor all was back to normal. On Fri, Oct 19, 2012 at 6:54 AM, Tom Curlee tcur...@sbcglobal.net wrote: I'll second the interesting part. I have a problem with a 10 GHz brick oscillator LO that I converted to GPS lock. I don't remember the instantaneous frequency jumps (around 200 - 400 HZ at 10 GHz) before I did the GPS lock (although it's possible). Please note that this is NOT any type of GPS phase shift. I built a extremely slow frequency lock circuit that has a loop time in seconds. The jump is instantaneous and I can then see the control voltage slowly change to correct the error. When the frequency jumps back, the control voltage slowly follows. Since this brick has the usual 106.5 MHz crystal (multiplied by 96 to get 10.224 GHz for the LO), I'm seeing at most 400 HZ / 96 shift in the crystal oscillator. I've wondered if I have a noisy varactor diode. The diode selected was one I had around, selected only because it had a low-ish capacitance value. I haven't gotten around to digging into the problem any farther. Anyone have any more info or ideas? 73, Tom WB6UZZ --- On Thu, 10/18/12, John Miles jmi...@pop.net wrote: From: John Miles jmi...@pop.net Subject: Re: [time-nuts] HP 10811 Tuning Diode To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Date: Thursday, October 18, 2012, 8:54 PM That's extremely interesting, Adrian. I've never heard of a noisy varactor, but then I've never looked for one, either. It'd be great if some of the problems that have been blamed on jumping crystals were in fact caused by the tuning diode. What steps did you take to rule out the crystal and narrow down the problem to the diode? -- john, KE5FX Miles Design LLC -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Adrian Sent: Thursday, October 18, 2012 12:19 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] HP 10811 Tuning Diode Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
Rick, thanks for the hint. I had a 2x 45 pF SOT23 diode at hands that works fine. The frequency could be adjusted without any changes to the circuit. Now as the 10811 is back in the 8662A, the diode will most likely keep living happily in there. John, it's a bit tricky. First of all, you need a fast phase noise display like the 3048A spot measurement. Otherwise you have no (almost) immediate indication of changes and only get the average noise over a longer period displayed, which, of course, also indicates that there is something wrong. For intermittent and temperature dependent failures, a little heat plus freeze spray can do wonders. I used a SMD hot air soldering tool that allows for selective heating. In this case, the excessive noise was limited to offset frequencies below a few kHz. It appeared to be filtered by the crystal. So, there wasn't that much circuitry left, mostly the oscillator stage itself, the tunig circuit and power supply. Adrian John Miles schrieb: That's extremely interesting, Adrian. I've never heard of a noisy varactor, but then I've never looked for one, either. It'd be great if some of the problems that have been blamed on jumping crystals were in fact caused by the tuning diode. What steps did you take to rule out the crystal and narrow down the problem to the diode? -- john, KE5FX Miles Design LLC -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Adrian Sent: Thursday, October 18, 2012 12:19 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] HP 10811 Tuning Diode Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
Hi Varactors are typically biased through very large decoupling resistors. The amazing part isn't that they get noisy, it's that they ever are quiet :).. In most circuits if they ever leaked at the rated max leakage spec, you would see all sorts of trouble. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of John Miles Sent: Thursday, October 18, 2012 11:55 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] HP 10811 Tuning Diode That's extremely interesting, Adrian. I've never heard of a noisy varactor, but then I've never looked for one, either. It'd be great if some of the problems that have been blamed on jumping crystals were in fact caused by the tuning diode. What steps did you take to rule out the crystal and narrow down the problem to the diode? -- john, KE5FX Miles Design LLC -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Adrian Sent: Thursday, October 18, 2012 12:19 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] HP 10811 Tuning Diode Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
I wonder if the glass case got a crack in it or if the kovar seal was failing. Maybe a failed solder joint (which gets fixed when you install the new diode). I've never heard of a noisy varactor before either. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
I do not know the circuit in question but could you unsolder the varactor, solder in a 10pF cap and look at the output? The frequency would not be stable but if the varactor was the culprit, you should see less noise. My 2¢ anyway DaveH -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rick Karlquist Sent: Friday, October 19, 2012 11:01 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 10811 Tuning Diode I wonder if the glass case got a crack in it or if the kovar seal was failing. Maybe a failed solder joint (which gets fixed when you install the new diode). I've never heard of a noisy varactor before either. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
Slightly off topic: the oscillator transistor has some 1854- part number, but is actually a 2N5179 selected for some minimum fT at 30 mADC collector current. When the oscillator starts up, before the ALC takes effect, a fairly large DC current can flow and some 2N5179's don't have enough gain to start oscillating. The startup current isn't very well controlled. This info from one of the 10811 designers. I have a few 100 pF 10% glass varactors in my junk box if you can't get them anywhere else. The spec is the same 2X capacitance from 4 to 25 V, but a different - number because of the 10%. They are probably at least 30 years old! Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
I didn't notice any damage, nor was there a visibly bad solder joint. However, I couldn't reproduce the excess noise with a quick bench test at 30V / 100k neither. DC-wise there are a few microvolts only. Same with the SMD diode. Exept, when the original glass diode is exposed to light. With a LED Maglite, I got up to 50 mV (across 100 kOhm) out of it! But there is no light shining inside of a 10811, is there? I had first suspected a 0.1 ceramic cap, but that didn't cure the phase noise desease. The diode in the original circuit appeared to be heat sensitive, and the excess phase noise has gone away since I replaced the diode. The noise was clearly there, and it was also there using a test adapter and two lab power supplies. Adrian Rick Karlquist schrieb: I wonder if the glass case got a crack in it or if the kovar seal was failing. Maybe a failed solder joint (which gets fixed when you install the new diode). I've never heard of a noisy varactor before either. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
Hi The normal 10811 package has several openings in it. Light *might* get in there. A micro volts level of noise can mess up your phase noise if it's AC noise at a low frequency. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Adrian Sent: Friday, October 19, 2012 4:10 PM To: rich...@karlquist.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 10811 Tuning Diode I didn't notice any damage, nor was there a visibly bad solder joint. However, I couldn't reproduce the excess noise with a quick bench test at 30V / 100k neither. DC-wise there are a few microvolts only. Same with the SMD diode. Exept, when the original glass diode is exposed to light. With a LED Maglite, I got up to 50 mV (across 100 kOhm) out of it! But there is no light shining inside of a 10811, is there? I had first suspected a 0.1 ceramic cap, but that didn't cure the phase noise desease. The diode in the original circuit appeared to be heat sensitive, and the excess phase noise has gone away since I replaced the diode. The noise was clearly there, and it was also there using a test adapter and two lab power supplies. Adrian Rick Karlquist schrieb: I wonder if the glass case got a crack in it or if the kovar seal was failing. Maybe a failed solder joint (which gets fixed when you install the new diode). I've never heard of a noisy varactor before either. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
As I mentioned, the varactor is equivalent to the Motorola MV1650. I have a bunch as well left over from building VCXOs. :-) David On 10/19/12 3:37 PM, Rick Karlquist wrote: Slightly off topic: the oscillator transistor has some 1854- part number, but is actually a 2N5179 selected for some minimum fT at 30 mADC collector current. When the oscillator starts up, before the ALC takes effect, a fairly large DC current can flow and some 2N5179's don't have enough gain to start oscillating. The startup current isn't very well controlled. This info from one of the 10811 designers. I have a few 100 pF 10% glass varactors in my junk box if you can't get them anywhere else. The spec is the same 2X capacitance from 4 to 25 V, but a different - number because of the 10%. They are probably at least 30 years old! Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
Rick, Adrian, I think there are a number of possibly material related areas that could cause a varicap to go noisy but I have no experience of them First a reversed biased diode makes quite a good particle detector :-)) and remanent radioactive atoms in say the glass could cause localised avalanches. This would seem unlikely because it would affect a whole batch but possible. I also wonder what the effect of strain, crystaline dislocations etc might do to the very small current flowing in a very high impedance. These can lead to odd effects when they penetrate the junction.. It could just be an unfortunate sample. I suspect the level of noise current is way below any specified meaured value. Alan G3NYK - Original Message - From: Adrian rfn...@arcor.de To: rich...@karlquist.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, October 19, 2012 9:10 PM Subject: Re: [time-nuts] HP 10811 Tuning Diode I didn't notice any damage, nor was there a visibly bad solder joint. However, I couldn't reproduce the excess noise with a quick bench test at 30V / 100k neither. DC-wise there are a few microvolts only. Same with the SMD diode. Exept, when the original glass diode is exposed to light. With a LED Maglite, I got up to 50 mV (across 100 kOhm) out of it! But there is no light shining inside of a 10811, is there? I had first suspected a 0.1 ceramic cap, but that didn't cure the phase noise desease. The diode in the original circuit appeared to be heat sensitive, and the excess phase noise has gone away since I replaced the diode. The noise was clearly there, and it was also there using a test adapter and two lab power supplies. Adrian Rick Karlquist schrieb: I wonder if the glass case got a crack in it or if the kovar seal was failing. Maybe a failed solder joint (which gets fixed when you install the new diode). I've never heard of a noisy varactor before either. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
Back in the dark ages while dinosaurs roamed the earth, I worked for a music audio company outside of Seattle, WA called Tapco (they are now Mackie). They were making PA amplifiers and I and three other people were doing final test and burn-in. Had one that had a bit of a 60Hz hum on the output. I took the cover off and the hum went up. Reached over to grab a scope lead and the hum died back down. Turns out one of the plastic transistors had a bubble in the case and the fluorescent lighting was hitting the junction. DaveH -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Friday, October 19, 2012 13:20 To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] HP 10811 Tuning Diode Hi The normal 10811 package has several openings in it. Light *might* get in there. A micro volts level of noise can mess up your phase noise if it's AC noise at a low frequency. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Adrian Sent: Friday, October 19, 2012 4:10 PM To: rich...@karlquist.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 10811 Tuning Diode I didn't notice any damage, nor was there a visibly bad solder joint. However, I couldn't reproduce the excess noise with a quick bench test at 30V / 100k neither. DC-wise there are a few microvolts only. Same with the SMD diode. Exept, when the original glass diode is exposed to light. With a LED Maglite, I got up to 50 mV (across 100 kOhm) out of it! But there is no light shining inside of a 10811, is there? I had first suspected a 0.1 ceramic cap, but that didn't cure the phase noise desease. The diode in the original circuit appeared to be heat sensitive, and the excess phase noise has gone away since I replaced the diode. The noise was clearly there, and it was also there using a test adapter and two lab power supplies. Adrian Rick Karlquist schrieb: I wonder if the glass case got a crack in it or if the kovar seal was failing. Maybe a failed solder joint (which gets fixed when you install the new diode). I've never heard of a noisy varactor before either. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] HP 10811 Tuning Diode
Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
That would be a Motorola MV1650 or equivalent. You may have to select for 100pf +/- 5% @ 4V as the standard spec is 10% but it probably does not matter as the tuning ratio will be greater than the 2 spec. David On 10/18/12 3:18 PM, Adrian wrote: Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
Probably unobtainium. 0122-0244 is shown as Motorola SMV315-24 or MSI Electronics SQ529. For whatever that's worth. Reminds me of a popular audio amplifier design that was in Popular Electronics using Motorola SS1122 diodes. Some special non catalog diode. Turns out Dan Myers, the designer, just happened to have these in his junk box. A gazillion other diodes would also work. In the 5071A, we used a 10811 with a different tuning diode that gives a 10X larger range and is linear tuning (being hyperabrupt). There is nothing magic about the 0122-0244. Lots of diodes can work. Rick Karlquist N6RK Adrian wrote: Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
That's extremely interesting, Adrian. I've never heard of a noisy varactor, but then I've never looked for one, either. It'd be great if some of the problems that have been blamed on jumping crystals were in fact caused by the tuning diode. What steps did you take to rule out the crystal and narrow down the problem to the diode? -- john, KE5FX Miles Design LLC -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Adrian Sent: Thursday, October 18, 2012 12:19 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] HP 10811 Tuning Diode Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 10811 Tuning Diode
I'll second the interesting part. I have a problem with a 10 GHz brick oscillator LO that I converted to GPS lock. I don't remember the instantaneous frequency jumps (around 200 - 400 HZ at 10 GHz) before I did the GPS lock (although it's possible). Please note that this is NOT any type of GPS phase shift. I built a extremely slow frequency lock circuit that has a loop time in seconds. The jump is instantaneous and I can then see the control voltage slowly change to correct the error. When the frequency jumps back, the control voltage slowly follows. Since this brick has the usual 106.5 MHz crystal (multiplied by 96 to get 10.224 GHz for the LO), I'm seeing at most 400 HZ / 96 shift in the crystal oscillator. I've wondered if I have a noisy varactor diode. The diode selected was one I had around, selected only because it had a low-ish capacitance value. I haven't gotten around to digging into the problem any farther. Anyone have any more info or ideas? 73, Tom WB6UZZ --- On Thu, 10/18/12, John Miles jmi...@pop.net wrote: From: John Miles jmi...@pop.net Subject: Re: [time-nuts] HP 10811 Tuning Diode To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Date: Thursday, October 18, 2012, 8:54 PM That's extremely interesting, Adrian. I've never heard of a noisy varactor, but then I've never looked for one, either. It'd be great if some of the problems that have been blamed on jumping crystals were in fact caused by the tuning diode. What steps did you take to rule out the crystal and narrow down the problem to the diode? -- john, KE5FX Miles Design LLC -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Adrian Sent: Thursday, October 18, 2012 12:19 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] HP 10811 Tuning Diode Hello, I found the 10811 in my 8662A to be quite noisy and was able to trace the problem down to the tuning diode. Actually, the phase noise started to jump when the oven heated up. As a quick solution, I replaced it with a SMD type that I had at hands. I would appreciate any hint where to find an original diode (even though I could leave it as is). As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% C4/C25-MIN=2 BVR-30V Mfr. 28480' Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and '0244' and '312'. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
