[time-nuts] Entry level systems

John Ackermann N8UR jra at febo.com
Wed May 24 18:31:38 EDT 2006

Keith E. Brandt, M.D. said the following on 05/24/2006 06:06 PM:
>    What's a good entry-level time reference system? I'm doing this for
>    the fun/learning/hobby and can't dump $10k into it (without also
>    incurring the attendant lawyer's fee for the divorce settlement :-)
>    I think something along the lines of the TAPR TAC would be perfect if
>    they still made it. Are there other relatively low-cost GPS reference
>    systems out there?

Interesting question!

Assuming you mainly want to have a test-bed for learning and
experimentation, I'd say you want three things:  1) a local frequency
standard, 2) a frequency/time interval counter, and 3) a GPS or other
radio reference.

For the frequency standard, one of the surplus HP 10811A or 10544A oven
crystal oscillators ("OCXO") which can be had on eBay for $50 - $150
would be good, or one of the surplus Efratom Rubidium standards that go
for the $250 range -- each has its own advantages; the crystal will have
better short term stability and less phase noise, but the Rb will have
better long term stability and will need to be recalibrated far less often.

For the frequency counter/time interval counter, I am very partial to
the HP 5334A or B.  They are quite cheap on eBay (usually less than $150
and have 2ns time interval resolution.  As a bonus, many of them have
the high-stability option (001) that includes an HP 10811A oscillator,
and if you find one with the "channel C" option you will be able to read
frequency to 1.3GHz.

Finally for the GPS.  We're in a state of flux right now because
Motorola sold their line of GPS receivers and the one everyone would
have recommended last year is no longer available.  Nonetheless, you may
be able to find an M12+T receiver which is the best unit they had
available, or the slightly older UT+.  You'll need an antenna, but you
don't necessarily need the TAC-2 -- all it really does is provide power
supply and I/O buffering.  You can do that on a piece of perfboard if
you want.

There are lots of other neat toys, but with those three you'll have a
good frequency standard and a way to calibrate it.

Hope this helps.


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