What do people observe on their 5370A/Bs?  After warmup, I tend to see a
bias of about +0.0005 Hz, or 5E-11, when observing its own 10 MHz source.
There is some occasional random waffling on the order of about +/- 0.001 Hz
but for the most part it reads close to 10.000 000 000 5.

I have never been able to calibrate the interpolators (specifically the
anticoincidence adjustment) in these counters, due to lack of a
vernier-adjustable pulse generator.  When I was going through one last week,
I just left the anticoincidence pot in the middle of its range, and couldn't
see any ill effects from doing so.  The manual is not that great at
describing exactly what this adjustment does.

-- john, KE5FX

That was with an external 10 MHz source with both rear-panel reference and
front-panel Ch B inputs fed from a passive 4:1 splitter, by the way.
Feeding the EXT reference output directly to Ch B through a 6' cable results
in an average reading much closer to exactly 10 MHz.

-- john, KE5FX

On Thu, Feb 22, 2007 at 12:29:35PM -0800, John Miles wrote:

Mine is off more (or was until it died a couple of weeks ago).   But

I have yet to attempt the full cal procedure for reasons similar to yours.

I did find that using GPSDO 10 mhz the error was quite stable

(always reading low in my case, not high) but apparently just barely within
the spec in the manual.

--
Dave Emery N1PRE,  die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

John Miles wrote:

John

Connecting the frequency output to the Frequency/period input (set to 50
ohm) with a 1m double screened RG58 cable displays a frequency of
10.000000004 with rms fluctuations of about 2 in the last digit.  This
occurs right at start before any warmup with an HP5370A that doesn't
have an HP10811 or equivalent internal oscillator. oscillator.

Bruce

It's worth keeping in mind a couple of things:

1. The firmware in the 5334B is identical to the 5334A except
   for an extremely minor change to accommodate a different modulus
   in the C channel.

2. The entire program has to fit into 2KB (two thousand and
   forty eight bytes) of ROM, and was written in assembly language and/or
   machine language and is understandable only to its author (Ken T.)
   It uses every last byte of memory.  The 2KB limit is due to
   the legacy, discontinued microprocessor that was used (long story).

3. The interpolator has somewhat questionable accuracy when you
   get down to 12 digits.  This is hidden somewhat by the firmware,
   but if you monitor the bits the interpolator puts out, you can
   see what is going on.  To me, it is kind of amazing it works as
   well as it does considering the design.

So please lower your expectations!

If you want a really good HP counter, move up to the 53181 which
is much more modern, even being 15 years old.

Rick Karlquist N6RK
R&D Project Manager of 5334B (circa 1986)

Hal Murray wrote:

Hi,

I check my 5370b by using the 10 MHz output and feeding it to the counter.
What I see is a fluctuation in the displayed reading of between 9.999 999
998 73 to 9.999 999 997 25.  The instrument is set for 1 s gate. Sometimes
one reading will remain for a couple of arming but usually the reading will
change between six different readings with the high and low as above.

I am assuming there is a problem with this instrument and am asking for
suggestions on what can be done to correct this problem.

Ps. this instrument has the 10811-06111 oscillator.  I have tried using the
10 MHz output from the 5370 as an external reference to a 53131A while
measuring the frequency of the 5370 10 MHz output.  After both instruments
warm up the frequency of the 5370 output is displayed on the 53131A with a 1
s gate time as 10.000 000 000  and if I increase the gate time to 10s the
reading is 10.000 000 000 0 with the reading remaining rock solid.

Thanks,

Jeff

----- Original Message -----
From: "John Miles" jmiles@pop.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Thursday, February 22, 2007 3:29 PM
Subject: Re: [time-nuts] Fine print on HP 5334B

In message 003f01c75755$d2d9e340$0200a8c0@DESKTOP, "jshank" writes:

The manual is online in PDF somewhere and it has a nice and
simple to follow procedure, provided you have instruments which
are suitable substitutes what it prescribes.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Poul-Henning Kamp wrote:

Service manuals (5370A and 5370B) are at
www,ko4bb.com/ham_radio/Manuals/

Didier KO4BB