[time-nuts] Setting Osc Frequencies
vk3yv at netspace.net.au
Fri Mar 2 22:45:18 EST 2007
HI Tom, I realised when I read your reply that I had not said how I was
observing the result. I am feeding these signals into a 100 MHZ CRO not a
counter and visually observing the 2 signals in relationship to each other.
1 being the Trimble which I believe to be good to 3 parts in10^12 and the
Sulser up in the 10^11 range..Have a couple of HP5245L counters but I have
not arranged an external reference for them yet.
I hope that clears up what I am doing.
Regards, Don VK3YV....
----- Original Message -----
From: "Tom Van Baak" <tvb at leapsecond.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Saturday, March 03, 2007 1:40 PM
Subject: Re: [time-nuts] Setting Osc Frequencies
>> HI All , first time request. I wish to know how I can accurately set some
>> oscillators on frequency. I have 3 Sulzer oscillators .. 1 x 2.5A and 2 x
>> 2.5C's and 1 matching P/S with dead nicads.
>> My main reference is a Trimble Thunderbird which was the second source
>> the HP unit was used in cellular phone installations in the US a while
>> ago I
>> think that they maybe Nortel pulls like the HP's that were around.
>> I have tried in the past by putting the main reference into input "A" and
>> triggering 1 cycle of 10 MHZ and feeding one of the other oscillators
>> input "B" and adjusting the Sulzer to be totally overlaid with no
>> over many hours.. All Sulzers had been on for 36 hours before the
>> the Trimble has been on for 2 years.
>> What accuracy can I expect from this method, and is there a better method
>> with the equipment I have.
>> Regards, Don VK3YV.......
> It would depend on the specs of the time interval or frequency
> counter you're using. You mention, 1 cycle of 10 MHz; that's
> 100 ns. And you mention "many hours". The upper limit based
> on that alone is 100 ns over, say, 10 000 seconds which gives
> you a resolution of 1e-7 / 1e4 seconds = 1 part in 10 to the 11th.
> That's than enough accuracy, since, during that couple of
> hours a 36-hour warmed-up Sulzer will likely have drifted in
> frequency by about that amount.
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