Larry Gadallah wrote: > On 2/28/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> > wrote: >> Message: 6 >> Date: Thu, 01 Mar 2007 12:05:38 +1300 >> From: Dr Bruce Griffiths <[EMAIL PROTECTED]> >> Subject: Re: [time-nuts] Good Phase-noise? >> To: Discussion of precise time and frequency measurement >> <[email protected]> >> Message-ID: <[EMAIL PROTECTED]> >> Content-Type: text/plain; charset=ISO-8859-1; format=flowed >> >> Larry Gadallah wrote: >> > Hello all: >> > >> > I considering a do-it-yourself GPSDO, and I started by looking for a >> > good OCXO. I have been given a quote for a unit with the following >> > phase-noise numbers: >> > >> > -120 dBc/Hz at 10 Hz >> > -145 dBc/Hz at 100 Hz >> > -155 dBc/Hz at 1 kHz >> > -160 dBc/Hz at 10 KHz >> > -160 dBc/Hz at 100 KHz >> > >> > My question is this: Are these good specs? They look pretty good to >> > me, quite comparable to the HP 10811 numbers. >> > >> > Thanks, >> > >> Larry >> >> Whilst these phase noise figures are around 20dB or so worse than the >> state of the art, they are adequate. >> The short term frequency stability is determined more by the OCXO's >> Allan variance as a function of averaging time. >> In particular the Allan variance for averaging times from 1 sec to 1000 >> sec or more is significnt. >> >> Bruce > > Hello Bruce: > > Thanks for your comments. I should have mentioned that these numbers > were from a COTS OCXO, and that it is priced in the $200 range. > Ignoring the price, can you obtain 20 dB better performance from a > COTS device? Is it better to simply look for a good HP 10811 (in this > price range)? > > I understand the issue of Allan deviation versus frequency stability, > but my main purpose for this oscillator is as a local oscillator > reference for radios, where increased phase noise quickly causes the > receiver performance to degrade. > > Cheers,
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