[Lowfer] GPS-based Frequency Standard

Tue, 1 Jan 2002 09:17:38 -0500

Hello Marco,

Very interesting email, and it will quite helpful for those looking to
increase stability of there TX or RX system.

I noticed that you use a HP Z3801A  GPS Standard.  I am using a HP 58533a
here and it is great.  I have a friend who recently acquired a HP Z3801A and
is having trouble communicating with it.  Since it uses RS-422 instead of
RS-232 he needs to run a converter.  He is using a passive one and is having
no luck
talking to the module or even getting commands to echo back from it.    The
unit powers up and has no fault light on.  This unit came from 4000 miles
away and according to the manual needs to be reset to the new location.

Is there a hardware reset( we cannot find it)

Do you use a passive or powered converter?

Are   you familiar with the SCPI commands?

Any help to get this going would be much appreciated

Thank you

Marco

Paulc
W1VLF

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-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Marco Bruno IK1ODO
Sent: Tuesday, January 01, 2002 5:42 AM
To: [email protected]
Subject: Re: [Lowfer] GPS-based Frequency Standard

Hello Dexter,

I reply also to the list, since I presume this may be of interest to others
in times of very narrow band communications.

The Brooks Shera project is very good, but not inexpensive.
For best results you need a Motorola UT+ GPS receiver. I bought it
new three years ago for about $200 including the antenna.
The PCB and components cost about $100, then you need a
stable OCXO. I use a surplus unit by Oscilloquartz, coming from
an Omega receiver. The best choice for cost vs. quality is an HP
10811A, contained in many instruments, of wich the more common
is the 5328A-H99 universal counter, available probably around $150.
Sometimes it contains the 10544A oscillator; if possible look for the
10811A, it has better stability, less noise and less power drain.

If you have to buy all the parts you spend about $450. The project is
not very complex, but you have to understand operation and tweek
with time constants and receiver settings, then monitor it for some
week to verify performance. From the point of view of a standard
frequency aficionado (as I am...) it is VERY interesting. For general
purpose use it is quite complex to manage; but when it works you
forget it.

Other possibilities are:
1) the HP 10811A alone. An excellent oscillator, and you may expect
some parts in 10^-8 per year from a good unit operated continuously.
But keep a spare unit... I've seen some of them "die" of quartz
inactivity. And you must have access to a primary standard for
tuning and checking it.
2) a Rubidium standard. A cheap one is worth $200-250 (check Ebay).
You get probably some parts in 10^10/year from an Efratom M100,
but again you need a way of checking it (need a Cesium!)
3) a Cesium standard. Now, it's a primary one!. Absolutely not
suggested to the average amateur, since the initial cost may be low
(some $2000 or $3000), but the tube has short life and it is VEEERY
expensive.
4) an HP Z3801A. An embedded GPS standard frequency receiver like
the Brooks Shera project, but simpler to use and already boxed!
You add power, a PC and a GPS antenna, and get 10 MHz.
Performance very close to the Brooks Shera project, cost about $450
on Ebay, varying availability.  I have one working at the QRL, and I am
happy about it. I use it to check the long term stability of our Cs and Rb,
and it is a good performer.

If you need more info, let me know.

73 - Marco IK1ODO

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