[Test-Equipment] TM4520 inductors

[Jeff Furman]

Stewart, those inductors are Q standards used for calibrating Q meters. I 
didn't recognize the description until I saw the familiar pictures on the 
AADE site. I have a collection of the Boonton coils. Mine are labelled 
with the inductance and Q at a specified frequency. Since the Boonton 160 
covers a considerable frequency range, there are preferred inductance 
values for different frequencies, for example, a 2.5 millihenry inductor 
would be used at 100khz, but a 1 microhenry inductor would be  better at 
30 MHz. A Q meter has enough  variables that you need confidence testing 
before serious measurements. 
The Boonton coils are carefully measured and tweaked at the factory; I can 
guess similar ones are also worried as well.

You have a valuable find, worth much more because of their initial 
adjustment and calibration than is evident. I'm sure I purchased the coils 
I have in similar circumstances to yours.

73, Jeff AD6MX

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Does anyone know the original purpose and
rated frequency range for the Marconi TM4520
inductor set?

The individual coils are marked TM1438/letter

I have been using then to compare a number
of inductance meters with inconsistent results
and wondered about the construction, frequency range
and as they are in a nice polished box, whet their
provenance was. (I picked them up for pence at
a flea years ago because no one wanted them).

I note that they were used to calibrate the
AADE inductance meter

http://www.aade.com/lcm2binst/HP.html

and that they are a museum piece,

http://www.porthcurno.org.uk/html/arc_result.asp?SearchText=1438&sType=any&recNo=0

but I wondered if anyone knew any more.

Stewart/G3YSX