On 27 November 2014 at 22:38, Dr. David Kirkby (Kirkby Microwave Ltd) <[email protected]> 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
