[time-nuts] Entry level systems

John Day johnday at wordsnimages.com
Wed May 24 20:36:26 EDT 2006

At 06:31 PM 5/24/2006, John Ackermann N8UR wrote:
>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.

You will often find that it is cheaper to buy a counter with the 
high-stab oven option than to buy the oven separately.

>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.

The 5335A is also sold from about $100 up and has the oven option as 
opt010, 1.3GHz is opt030 and opt040 - expanded HPIB control is worth 
having if you plan to remote the counter at all.

A little heavier is the 5345A which can be equipped for operation all 
the way to 40GHz or so at not a huge expense. It is one of my all 
time favourites. It has 2ns resolution and counts direct to 500MHz. 
They came as standard with the high stab oven, opt001 removes the 
oven. Opt010 is very basic HPIB talk only, opt011 HPIB with remote 
programming, opt012 is HPIB like 011 but has control of slope and 
trigger level as well.

You can pay from $80 or so for basic counter with HPIB. Just get the 
seller to confirm it is not Opt 001! The 5345 is heavy, and a bit 
noisier than the newer 5334A/B or 5335A. To my m ind if you are 
interested in frequerncy measurement, this counter can give you 
flexibility well beyond anything else that mere mortals can afford 
when coupled with various plug-ins and convertor heads.

73's, John (ex VK3ZJF)

>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.
>time-nuts mailing list
>time-nuts at febo.com

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