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Old 18th Dec 2022, 11:10 am   #21
GMB
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Default Re: Marconi TF2701 In Situ RCL Bridge.

Quote:
Sorry to spoil your thoughts but all of the in situ settings on this bridge have a resistor in parallel with the capacitor.
None of them show a resistor in series with the capacitor.
That is not a restriction, merely the fact that it cannot distinguish between the two cases so presents the result in that form. If you know you want the series resistance then it is just maths to work it out (bearing in mind that it depends on the measurement frequency). I can't say I have tried so it may not be very accurate as capacitor ESR hopefully looks rather small (so EPR looks rather large).
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Old 18th Dec 2022, 4:40 pm   #22
Draker4c
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Default Re: Marconi TF2701 In Situ RCL Bridge.

Interesting thread could anyone tell me a source for the TF2701 manual? Google has nothing on it and the conversion tables would be really handy.
Hugh
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Old 19th Dec 2022, 11:49 am   #23
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Default Re: Marconi TF2701 In Situ RCL Bridge.

I have made a single page reference card from the graphs for the TF2701.
It's on my web site at http://air-ministry.uk
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Old 19th Dec 2022, 1:33 pm   #24
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Default Re: Marconi TF2701 In Situ RCL Bridge.

Greetings all.
(That's appropriate for this time of year.)

Thank you once again GMB for going to the trouble of producing the graphs on the one page.
Very useful for me.

Recently acquired a HP-4815A RF Vector Impedance Meter.
Got it going.
Used in conjunction with my TF-2701 bridge gives some interesting insight to why some things that should happen; don't.

Some years ago I built a book project of a 40 metre transceiver.
Could never get it to work. Tried everything. Ended in a box at the back of a back shelf and forgotten.
You know when you build a project and you need maybe 6 small parts you order 10. Round figure.
This project used small RF chokes for all of the DC feeds rather than resistor / bypass caps.

Just playing with the TF-2701 on random components from my workshop and in active repair jobs on the bench. Found a few left over feed chokes from the transceiver project. Chokes measured spot on for the correct value. (This is at the Marconi's test frequency of 80Hz.) (Can't remember the value).

Put them on the HP-4815A and they turned out to be self resonant at 7.095 Mhz. Quite a strong parallel resonance at that. All 6 of them! I guess this is why the radio project didn't want to work seeing as it was supposed to work in the 40 metre (7Mhz) band.

So just practicing with the Marconi bridge and the HP has been quite informative.

Thanks again to everyone that has responded to this thread.
I am quite enjoying my TF-2701.

Cheers all and the best for the season.
Robert. VK2BNM (VK2 Broke No Money.)
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Old 19th Dec 2022, 6:56 pm   #25
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Default Re: Marconi TF2701 In Situ RCL Bridge.

At RF pretty much any component does not behave like what it says on the can.

The question you always have to ask is "what frequency can it get to before it stops being what it says".

The answer is invariably a disappointment!
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Old 26th Dec 2022, 9:44 pm   #26
Draker4c
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Default Re: Marconi TF2701 In Situ RCL Bridge.

GMB many thanks for the pm and help.
73 Hugh G1AUR
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