[NLRS] 10 MHz frequency standards

[Donn - WA2VOI/0]

Oops, sorry.  I meant a few cycles at 10.368.

Also, be careful of prices "too good to be true."  They may be so "good" for a 
reason.

Now, if you're willing to accept the dial reading to be "where-ever" it falls at 
the 144 i.f. frequency, I'll posit that you'll do very well with almost any 
decent OCXO (NOT GPS stabilized) or a good TCXO.  However....

And yes, you're HP will have drifted some in the two years or so you've had it. 
EVEN IF ITS BEEN POWERED OFF.  The usual practice is that CXOs are always left 
on, and the drift rate established.  A correction can be applied when making 
measurements.  Also, when turning an CXO, it'll take 24-48 hours for it to 
stablize and COME BACK TO THE FREQUENCY it was at when turned off.  We're 
talking parts in 10-8 or 10-9 here, but thats what you expect with a standard if 
you want to measure 10GHz.

73 Donn

----- Original Message ----- 
From: <tosca005 at umn.edu>
To: "NLRS Reflector" <nlrs at mailman.qth.net>
Sent: Thursday, September 17, 2009 12:13 AM
Subject: Re: [NLRS] 10 MHz frequency standards




On Sep 16 2009, Donn - WA2VOI/0 wrote:

> An Rb will only put you within a few cycles (unless it, itself, is GPS
> disciplined), and MAY increase the phase noise.

Is this mis-typed, or do you mean within a few cycles of 10 MHz, or do you
really mean within a few cycles of 10,368,000,000 Hz? ? ? I guess I am
thrown by the use of the word "only" in this context, implying to me less
than stellar accuracy, but maybe you mean tiny (minisculem, actually)
inaccuracy?

> Rbs are also more
> expensive and, as Bruce notes, DO have a finite life. Those we get
> surplus could die tomorrow (or
>5 years from now... you don't know !).

I assumed the price would be much higher, but (a) surplus OCXO's seem less
plentiful and more expensive now than they used to be, and (b) I was
watching a Rb osc on eBay that was holding at an amazingly low price
without any serious bids, so I put in a bid of $50 and with 1 day to go, it
has only risen to $12 so far. Of course, the price could go anywhere up
from there in 24 hours' time, but I figured what the heck, why not try,
sometimes things go for dirt cheap? This model was apparently "designed for
a 10-year life" so I see exactly what you mean about having an unknown life
remainder on it. But even if it had a 1 year life remaining (90% used up),
and I run it for 48 hours at a crack times 6 or 7 contest weekends per
year, it will still take a while to use up that last year of life...

> The last issue is your i.f. radio's tuning accuracy. It doesn't do much
> good to be on 10.368.100 000 +/-1 (Rb) if the i.f. radio is off by 150 Hz
> (~1ppm) or 75 Hz (0.5ppm) and/or drifts like a bansee.

Much as I'd love, on principle, for 144.100 MHz to represent 10368.100 MHz,
I'd be quite willing to settle for a known offset that is something else,
but is constant. I have an HP frequency counter that has the high-stability
ovenized oscillator and was calibrated against a cesium standard before
sale to me, so I guess I can measure something that at least looks like
10,368,000,000 Hz on the display with it, but of course even that
oscillator must be subject to drift in the couple of years that I've owned
it. There is a 10 MHz external reference input jack which, I suppose, could
go to an even better standard reference to allow me to measure where the
combination of transverter, disciplined LO, and IF radio all conspire to
end up, and then write it down on a piece of tape stuck to the back of the
dish... :)

Thanks for the input.
73 de WØJT
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