[time-nuts] Upgrade an HP 5342A microwave frequency counter to have an oven oscillator.

Adrian Godwin artgodwin at gmail.com
Sat Nov 29 16:19:48 EST 2014

Is the upgrade similarly easy on a 53131A ?

I realise that it needs to have an additional controller pcb but I
have one of these counters fitted with option 001. The pcb holding the
oscillator has an edge connector that looks suitable for a 10811A, and
I have one to hand as well as a couple of compatible oscillators.

I think I would need to remove the existing TCXO module - I haven't
investigated too carefully yet but I think it's soldered in, and
obstructs the mounting of the 10811A.

On Sat, Nov 29, 2014 at 5:20 PM, Dr. David Kirkby (Kirkby Microwave
Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> On 27 November 2014 at 22:38, Dr. David Kirkby (Kirkby Microwave Ltd)
> <drkirkby at kirkbymicrowave.co.uk> wrote:
>> The HP 5342A has an optional oven oscillator. I just bought one of
>> those counters, but mine has a TCXO and is about 50 kHz off at 10 GHz.
>> I'm sure I can trim it closer than that, but if possible I'd like to
>> stick an oven oscillator in it. Does anyone know what is involved? I
>> have at least one 10811A oscillator here that I could stick inside,
>> but does it need any more, or just the oscillator?
>> Someone said the oscillator should be an 10544-60011, but a 10811A is
>> backwards compatible.
>> Dave
> It was very easy to fit the 10811A oven (HP 10811-60111) and get the
> oven working, although the oven is not powered when the counter is not
> switched on, even if there is power at the AC mains input. I can live
> with that. In fact, I prefer it to be honest.
> The procedure was
> 1) Remove top and bottom covers, which means the two front feet, plus
> 4 rear feet/protectors need to be removed.
> 2) Undo one screw at the top that held a board with a TCXO on it. The
> board plugs into a 15-pin edge connector.
> 3) Pull out the board (HP P/N 05341-60047) with the TCXO. The TCXO on
> the board is a marked  DALE, TCXO-22-1, 0960-0394, 10.0MHz, SET 1.0Hz.
> (normally I would put a space between a number and the units, but I've
> written what is actually on the TCXO).
> 4) Attempt to insert the 10811A oscillator. This failed, as there were
> some wires around the optional board for GPIB which were restricting
> the space too much. So I had to cut a wire tie, and move the wires out
> the way.
> 5) Fitted 10811A at the top.
> 6) Invert the counter, and screw in the two screws which secure the
> 10811A to the chassis. For this I needed to temporarily move a ribbon
> cable, as the screw was below it.
> 7) Powered it up, and it worked. It shows "OVN" in the right of the
> LED display. Once that went out, it still took a minute or two for the
> readings to become pretty stable, although no doubt it will take
> months to become as good as it will get.
> I've not adjusted it yet, as I don't have any accurate frequency
> reference. But whilst the actual frequency indicated on the counter is
> different from what my signal generators are supposed to be producing,
> the last few digits (100, 10 and 1 Hz), are not all jumping around
> when seeing 10 GHz.
> The frequency indicated on the counter when connected to two different
> signal generators, which both have ovens of unknown type, are:
> 1) HP 83623A 20 GHz sweeper set to 10.0 GHz, fed into high frequency
> input of the frequency counter.
> HP 5342A counter indicates 10,000,000,690 Hz (relative difference = +6.9 10^-8)
> 2) HP 8656A set to 100 MHz,
> HP 5342A counter indicates 99,999,987 Hz (relative difference = -1.3 x 10^-7)
> With the old TCXO in the frequency counter, the indicated frequency of
> the 10 GHz signal was about 48 kHz off, but it moved around a KHz or
> so. In contrast, now the oven is installed, the reading is a *lot*
> more stable, with it shifted about 15 Hz.
> I don't currently know the absolute accurate any of the references in
> the test equipment are, but certainly the readings are a lot more
> stable after fitting the oven.
> I will need to get a GPSDO before adjusting any, but if nothing else,
> the short term stability of the oven is clearly superior to the TCXO.
> Long term should be too, but I can't determine that from what I have.
> Dave
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