[time-nuts] need recomendation for a portable 10mhz referenceoscilator
SAIDJACK at aol.com
SAIDJACK at aol.com
Wed Dec 12 17:36:37 EST 2007
In a message dated 12/12/2007 14:11:50 Pacific Standard Time,
rmoncur at bigpond.net.au writes:
>Now I am not sure which of any of the above points are necessary or
>important but I would be grateful for the thoughts of others.
>Regards Rex VK7MO
Hi Rex,
that's a lot of great information! Since you are not too concerned about
overall frequency accuracy (I assume 1 to 5E-09 would be acceptable) you may not
need to or want to lock to GPS at all. With a typical OCXO retrace of 5E-09
you would have a (fairly stable) frequency offset of 235Hz or so at 47GHz.
As you mentioned your requirement to be ~2Hz deviation at 47GHz this
calculates to about 4.3E-011 stability over 46 seconds.
GPS itself cannot deliver that, but a good OCXO flywheel will do that. Any
GPSDO with ADEV better than 5E-011 should be sufficient locked to GPS or not,
but you may have to keep the oven on at all times as you said.
Tom measured the Fury's ADEV (double oven) to achieve this performance above
measurement intervals of 0.01 seconds already so that should work really
well, and in this short time frame (46 seconds) it's pretty much all up to the
OCXO (aging and tempco correction by the processor should not be a factor at
46s intervals either).
Thus a good MTI double oven OCXO should do the trick for you and GPS locking
is not really needed, except maybe for getting initial frequency accuracy.
The advantage of this is that a typical MTI Eurocan double-oven OCXO
consumes only about 1.7W and can thus be safely and easily powered by a car battery.
bye,
Said
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