[time-nuts] Upgrade an HP 5342A microwave frequency counter to have an oven oscillator.
kb8tq at n1k.org
Sun Nov 30 11:38:34 EST 2014
If you *need* portability, an internal oscillator is a good thing. If you want to fire something up fast, an OCXO is not a good choice. That’s a bit of a problem.
A few real choices:
1) Get something like the LTE that locks up to GPS and runs right away. When portable, bring along a small GPS antenna.
2) Run a TCXO in the counter while portable and an external reference on the bench.
3) Power up the counter with internal OCXO the night before any “portable” measurements.
There really aren’t a lot of other options unless you head off into the portable atomic clocks.
> On Nov 30, 2014, at 11:08 AM, Götz Romahn <goetz at g-romahn.de> wrote:
> if you do not insist on a hp10811A, have a look at Gerrys site
> You can buy an assembled option 10 compatible OCXO modul for less than 100 GBP.
> I built DIY one with a PCB from Gerry using my Morion MV89 OCXO and it is working fine. Fully compatible with hp53131 calibration procedure.
> Am 29.11.2014 22:19, :
>> 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.
>>> 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.
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