Re: [time-nuts] noisy varactor diodes

2012-12-20 Thread Alan Melia
The HP sceme in the patent refers to an array of series and parallel diodes to reduce noise. Just paralleling them does not reduce the noise! Might this not depend what the type of noise was ?? JRC use this technique in the RF stage of their receivers but I am wondering if this is only valid

Re: [time-nuts] Noisy varactor diodes

2012-12-19 Thread Didier Juges
@febo.com Sent: Tue, December 18, 2012 1:32:11 PM Subject: [time-nuts] Noisy varactor diodes I was recently repairing a noisy A3 module for an HP 5065A. ... Anybody know where to get an MV840 ??? Thanks, Corby ___ time-nuts mailing list -- time

[time-nuts] noisy varactor diodes

2012-12-19 Thread cdelect
The HP sceme in the patent refers to an array of series and parallel diodes to reduce noise. Just paralleling them does not reduce the noise! The 4 paralleled in the 5065 are to give enough phase deviation for the low modulation level applied. (150mv) The symptom was a fluctuating 2nd

Re: [time-nuts] noisy varactor diodes

2012-12-19 Thread lists
-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] noisy varactor diodes The HP sceme in the patent refers to an array of series and parallel diodes to reduce noise. Just paralleling them does not reduce the noise! The 4 paralleled in the 5065

Re: [time-nuts] noisy varactor diodes

2012-12-19 Thread John Miles
The HP sceme in the patent refers to an array of series and parallel diodes to reduce noise. Just paralleling them does not reduce the noise! Still, the patent claims seem pretty obvious. Paralleling n diodes would reduce their noise contribution by the usual 3 dB * log2(n) factor, but

Re: [time-nuts] noisy varactor diodes

2012-12-19 Thread lists
time and frequency measurement'time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] noisy varactor diodes The HP sceme in the patent refers to an array of series and parallel diodes to reduce noise. Just

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread paul swed
Try these guys aiHave had luck on other parts. Aint cheap http://www.americanmicrosemi.com/information/spec/?ss_pn=MV840 Regards Paul WB8TSL On Tue, Dec 18, 2012 at 1:29 PM, cdel...@juno.com wrote: I was recently repairing a noisy A3 module for an HP 5065A. The phase modulator has 4 varactor

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread Ed Palmer
What are the horizontal and vertical settings for that picture? Ed On 12/18/2012 12:29 PM, cdel...@juno.com wrote: I was recently repairing a noisy A3 module for an HP 5065A. The phase modulator has 4 varactor diodes in parallel. Since I suspected a diode, I removed them one at a time. Of

Re: [time-nuts] Noisy Varactor diodes

2012-12-18 Thread paul swed
will say impressive let us no what american micro semi wants for a diode. I suspect a few of us may need them at some point On Tue, Dec 18, 2012 at 2:31 PM, cdel...@juno.com wrote: The vertical is 50Mv/cm and the horizontal is 1ms/cm The diode is connected to + 20VDC and then to a 20K

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread Robert LaJeunesse
Subject: [time-nuts] Noisy varactor diodes I was recently repairing a noisy A3 module for an HP 5065A. ... Anybody know where to get an MV840 ??? Thanks, Corby ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread paul swed
Good find on the diodes and as you say at least worth the try. Will bet they are 10 x less expensive then americanmicrosemi. But I will say in a pinch they bailed me out. :-) Tunnel diode for a TDR. Regards Paul. On Tue, Dec 18, 2012 at 2:55 PM, Brooke Clarke bro...@pacific.net wrote: Hi Corby:

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread paul swed
John 2 with the same type of issue that is bad luck or simply age. Oh my do I for see this in my future? I would be willing to bet it exactly looks like your description. I like the fact that for $1.23 you can get something from digikey. I do tend to trust them and mouser. Regards Paul. On Tue,

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread David
On Tue, 18 Dec 2012 16:51:02 -0500, paul swed paulsw...@gmail.com wrote: John 2 with the same type of issue that is bad luck or simply age. Oh my do I for see this in my future? I would be willing to bet it exactly looks like your description. I like the fact that for $1.23 you can get something

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread David McGaw
I have tried to work with 4 Star Electronics. They only want to deal with large quantity orders. I would be interested to hear if anyone has had better luck. David N1HAC On 12/18/12 4:42 PM, John Miles wrote: [1]www.octopart.com identifies 23 of them in stock at a reseller

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread Gerhard Hoffmann
Am 18.12.2012 22:42, schrieb John Miles: Just curious, what was the 5065A acting like with the bad diode? Mine seems to run quietly for days at a time, but then occasionally it generates excess low-level random noise for a period of hours to days (see image). Every time I've tried to get

Re: [time-nuts] Noisy varactor diodes

2012-12-18 Thread gary
HP has a patent on this scheme. The paralleling of the diodes is for noise reduction. Personally, I would have rejected the patent since this is the kind of thing that is obvious to those skilled in the art.