Tom,

it is the old good ARRL noise bridge. It has a pot in its output bridge
circuit.
I changed the layout of the elements a little from what is in the Handbook,
and found it works reasonably well up to 50MHz. The signal is still audible
on 2m, but I did not concentrated on evaluation of the circuit on that band.
The original question came up because I had unacceptable results with the
carbon pots (they are not good at their minimum level). My hope was cermets
or plastic ones may have better stability.
Unless the pot is of a wirewound type, parasitic inductance of the element
could be compensated as described in the article.
And because the null can be very sharp, a multiturn pot would be of a big
help.

My best regards,
Ivan


"K7ITM" wrote in message
oups.com...
Hi Ivan,

Yes, I'd expect it to say its a hybrid pot in the data sheet. They
tend to be quite expensive.

What are you doing with this particular pot? It always helps in giving
a useful answer if we have all the relevant information, and "50MHz"
isn't a whole lot of information.

Cheers,
Tom