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27th January 2009 18:10

Alan Yates wrote...

Arv,

Thanks for that link. It is a very similar idea to what Mark suggested at the meeting, he was talking about drilling out a large soldering iron to make a solder pot. I have a large iron I don't use much, I might give that a go.

BTW Arv, that homebrew testclip idea is very creative!

Kevin,

I didn't pick the most flattering picture - sorry - but most of the others didn't show your face. :)

The helical calculator is one of my oldest calculators. I am still in the (stalled) process of converting the old calculators over to the new calculator engine which has much better input argument parsing. One of these years I might have completed half of the job... Like the site search engine and hetrodyne sweep generator I seem to have lost my motivation temporarily.

A transducer gain calculation jig would be handy wouldn't it... Something you pass the input through with a directional coupler to measure the input and terminate the device into to measure the output. Mismatch on the input would be a source of errors, so maybe you just sample the voltage and assume the Zo. If the detector has enough dynamic range you could switch the DUT in and out of the circuit periodically, a microcontroller or PC could facilitate calibration and zeroing. I guess the right way to do it is to level the input, pad it down then detect after passing through the DUT (so you have a real scalar network analyser). A SA + Tracking Generator is probably the best approach, but a DDS + Log Detector and some coax switches lashed up to the PC could do it. You don't even need the switches if you do equalisation in software from a run with the DUT replaced with a linear joiner. (As long as the source has a repeatable output amplitude, the Dickie-style switching scheme requires the source to only be short-term amplitude stable).

Regards,

Alan

27th January 2009 16:38

Kevin vk2zkb wrote...

Hi Alan, I didn't realise you had that helical cal on your website otherwise I would have used your's.

Nice shots of the T&T, (reminded me I need to lose some weight). I finished off the prototype of my RF power meter last night, unfortunately my RF gen output level varies quite a lot, I was thinking of having two power level meters, one monitoring the input level to the DUT and one on the output of the DUT, then having a voltmeter that calculates the ratio of the two outputs of the powermeters. (subject to how linear the power meter response against input level), This would save me having to manually adjust RF gen output level as much. Do you happen to have a circuit that would do That by any chance?

And thanks for the url to the things that flash and bang in the night.

Cheers

27th January 2009 07:17

Arv K7HKL wrote...

For a neat and inexpensive solder pot design, see http://www.qrpkits.com/files/MiniSolderPot.pdf