Re: Frequency reference lab standard

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Greg Broburg
Posts: 156
Joined: Sat Apr 28, 2018 6:48 pm

Re: Frequency reference lab standard

Post by Greg Broburg » Sat Oct 31, 2009 1:42 am

Hello Jim, Geoff,



I am studying your ideas here and there is one point that I do not

understand. Your design discussions involve a relatively high

performance oscillator in a phase locked loop where it seems to me that

there is no need to have very high performance in the oscillator. To

esxamine a bit farther, it seems to me that the value of having such a

high performance local oscillator is to be able to hold the adjusted

value without any signal from the satellite constellation over some

time. Heathkit had a design similar to this a couple of decades ago

where an oscillator was locked with a microprocessor to WWV at 5, 10,

and 15 MHz. The processor maintained the oscillator if the active one

was lost was lost and scanned to the others to another to try to find

lock there. To really see the value of these high performance

oscillators as shown in your lash ups I would suggest that there be a

digital voltmeter to see the final lock voltage and a manual trimpot to

bring the value to the osc tuning Voltage manually. But to be truly

suave about it, perhaps a little processor to handle the formalities and

monitor the locked loop Voltage and regenerate it with a fancy DAC.

Something like 12 bits to start or perhaps 8 bits coarse and 12 bits

fine for a mad hatters special. You can even try a bench experiment

where you build two and use one connected to a GPS antenna to identify

the performance of the unit that is running on its own steam.



To truly push the noodle perhaps a way to deliver a programmable output

frequency from the 10M0 could be conjured using a DDS ala a lift from

the spectrum analyzer project.



Any thoughts???



Greg





> Jim,

> I built a GPS disciplined Freq Ref based on G3RUH's designed too. I

> got good results using just an inexpensive TCXO. I am building another

> one now with a nice Isotemp OCXO 134-10 I got from eBay for $17.

> DJ

> Jim

> Take at look at the GPS disciplined oscillator designed by James Miller,

> G3RUH, http://www.jrmiller.demon.co.uk/project ... rqstd0.htm

>

>

> I built one to this design and it is rock solid when compared to the BBC

> transmitter at Droitwich and to the Rugby frequency standards.

>

> The GPS module came via e-bay for about 15GBP and the same for the 10MHz

> module.

>

> It has replaced the previous standard I used which was locked to the

> BBC TV

> line timebase, sadly not of any use now due to the digital

> transmission from

> studio to transmitter.

>

> Geoff

> ----- Original Message -----

> From: "Jim Hontoria"

> To: >

> Sent: Friday, October 30, 2009 7:40 PM

> Subject: [spectrumanalyzer] RE: Frequency Reference LAb Standard

>

> >I am in the early stages of the design of a GPS disciplined 10 MHz

> >frequency

> > reference. As local oscillator I would like to use the ICM temperature

> > controlled/ ovenized unit IVCTCXO1912 that has the following

> > characteristics:

> >

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