Marconi TF2603 calibration: a question.

[Skywave]

This thread has an association with the thread 'Assessing instrument indication errors' - but this one is much easier to write - and hopefully a lot easier to answer!

Recently, I acquired a Marconi TF2603: an RF electronic millivoltmeter. A initial inspection revealed that some repair work was required. Fortunately, nothing dramatic: the replacement of some calibration pre-set pots. I was also very relieved to discover that Marconi had built an item of test equipment where serviceability had been borne in mind for once! (Apart from the PSU!)

So, having replaced those components, a re-calibration was required - and the manual is very clear and exact about how to do this - which I what I've learnt to expect from Marconi Instruments. But one thing puzzles me: Marconi specify a test frequency of 200 kHz. Considering the wide freq. range of this instrument, why specify a freq. so relatively low? I would have thought something like 1 MHz - or even 10 MHz - would have been more appropriate.
I don't need to know: simply curious.

I know that some members have one of these in their collections of instruments. So, is there any member here who can provide the definite answer, please?
Thank you.

Al.

[ferrett]

H Skywave the frequence of 200kHz was specified because that was the frequency standard at Marconi Instruments. It was derived from the old radio 2 long wave carrier frequency. I know this because I used to calibrate them at Marconi in the 1970s.
Chris

[Skywave]

ferrett / Chris: thank you! That's as likely a "definite answer" that I'm ever going to get.

Al.

[Wendymott]

Al.... I have a spare Commutator chopper, for that equipment..... PM me if you want it...£3 postage only.
Wendy