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, -- Larry Gadallah, VE6VQ/W7 lgadallah AT gmail DOT com PGP Sig: 616D 4E52 CF1F 3FEC FFFB F11B 7DB9 C79A EA7E B25B _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
