[time-nuts] Brooks Shera's GPS standard or HP Z3801A??

David Kirkby david.kirkby at onetel.net
Mon Apr 25 16:43:46 EDT 2005

Tom Van Baak wrote:
> This issue comes up a lot. If weren't for the glut of
> surplus Z3801A I'm sure the situation would be very
> different. 


> Brooks Shera did a fine job with his project
> and reached a wide audience with its QST publication.

I was always under the impression it was published in QEX, the ARRL's 
more technical journal, but I see you are right, it was QST. One ham 
once said to me a typical QST article was "How to build a 12V 1A power 
supply using a 7812 voltage regulator". Clearly this was a bit different.

I would agree with you the article is excellent.
I don't get QST now, as I found it too childish, but that article, like 
many that appeared years ago, was very good.

It's a shame ham radio has been spoilt with 99% of people just spending 
money and not understanding anything.

> If your goal is a turn-key 10 MHz frequency standard
> with short-term stability under 1e-11 then a Z3801A
> is a good solution.

> If your goal is to build something yourself, to use parts
> you have already, to learn as you go, and achieve
> similar performance then use the Brooks Shera design.

Working out what my goal is not an easy task.

It started with the desire to stabilise an 18th century pendulum clock 
with a crystal!! I realised I needed a decent crystal, and some way to 
measure its frequency, and it sort of escalated from there.

The route I take might depend on the outcome of this eBay transaction of 
mine for the 18011A.

> If you're a time-nut you'll end up with both anyway so
> that you can compare them; the only question is which
> to get first. ;-)
> /tvb


BTW, there is a lady at work who is quite into clocks. I sent her an 
email today with your wristwatch, but she replied she did not think it 
would be too popular.

Dr. David Kirkby.

> ----- Original Message -----
> From: "Dr. David Kirkby" <drkirkby at medphys.ucl.ac.uk>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Sent: Monday, April 25, 2005 02:35
> Subject: [time-nuts] Brooks Shera's GPS standard or HP Z3801A??
>>I was going to build the GPS reference by Brooks Shera
>>and have bought the PCB and started populating it (not much yet).
>>But now I am wondering if buying a used Z3801A might not be a better idea.
>>My thoughts are:
>>1) Cost - the Z3801A will probably cost less than buying all the parts
>>for Brook's Standard. This is especially so, with me in the UK, where
>>shipping charges on lots of small items from the USA soon add up.
>>2) Medium term stability - the double oven in the Z3801A might be more
>>stable than an HP 18011A.
>>3) Flexability - Brook's standard can be customised to whatever you want.
>>4) Long term servicability - if one builds the standard oneself, one is
>>far more likely to be able to debug it if things go wrong. One can buy a
>>few of the chips, for spares, just in case one dies and becomes hard to
>>get. The chips on the board are not that expensive.
>>5) Jitter on GPS.
>>6) If one needs to buy a manual on the Z3801A, that will add to its cost.
>>Any other thoughts ????
>>Dr. David Kirkby PhD CEng MIEE,
>>Senior Research Fellow,
>>Department of Medical Physics,
>>Mallet Place Engineering Building,
>>Gower St,
>>University College London,
>>London WC1E 6BT.
>>time-nuts mailing list
>>time-nuts at febo.com
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

Dr. David Kirkby,

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/

More information about the time-nuts mailing list