[NLRS] GPS Disciplined Osc

[Chris Elmquist]

On Wednesday (11/25/2020 at 10:00PM +0000), Jon Platt via NLRS wrote:
> Thanks Chris and others for comments.  This may be useable for a GPS locked LO for my older DB6NT 10 GHz unit where the LO is crystal based at 106 MHz (as I recall).

Yes. That seems reasonable.  You may have to attenuate the output of the
GPSDO (since it is a CMOS 3.3V level) if you are going to drive into or
replace a crystal oscillator of some sort.

73, Chris NØJCF

> -----Original Message-----
> From: Chris Elmquist <chrise at pobox.com>
> To: Lloyd - N9LB <lloydberg at tds.net>
> Cc: nlrs at qth.net; 'Jon Platt' <w0zq at aol.com>
> Sent: Mon, Nov 23, 2020 1:40 pm
> Subject: Re: [NLRS] GPS Disciplined Osc
> 
> 
> Of note, the Leo Bodnar unit that Jon asked about is _very_ frequency
> agile on the phase locked output.  You can set it up, using a simple
> Windows app, for any output frequency between 400 Hz and 800+ MHz.  So,
> it's a little different than a GPSDO that has a fixed 10 MHz output.
> 
> I chose it for this reason because it is very simple to lock an older
> radio, such as the FT736, which needs a 20.48 MHz clock rather than
> anything close to 10 MHz.  I have already done similar on an IC-746PRO
> using a home built PLL for 32.0 MHz.  Had this "Mini GPS" been available
> long ago, I would have chosen it instead, programmed its output to 32.0
> MHz and been done with it.
> 
> The Mini GPS has pretty good phase noise characteristics too--
> 
> Typical phase noise at 10MHz output:
> 
> -70 dBc/Hz at 1 Hz
> -100 dBc/Hz at 10 Hz
> -125 dBc/Hz at 100 Hz
> -145 dBc/Hz at 1 kHz
> -150 dBc/Hz at 10 kHz
> -153 dBc/Hz at 100 kHz
> -155 dBc/Hz at 1 MHz
> 
> He uses an Si532x device as the programmable PLL following a U-Blox GPS
> receiver.
> 
> There is a review here of the dual-output Bodnar unit from which the Mini
> was derived.  The application software for setting up the Mini is very
> similar, if not identical,
> 
> http://leobodnar.com/files/Informal%20Evaluation%20of%20a%20Leo%20Bodnar%20GPS%20Frequency%20Reference.pdf
> 
> Chris NØJCF

-- 
Chris Elmquist