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. 73, John _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts