Topband: Re: core inductance and current

[Tom Rauch]

> What would happen if I just use a common standard choke of something
> between 100 and 500 uH?

Many physically larger chokes (rather than miniature molded types) are OK
for passing control currents.

If the choke core does not saturate from bias current and the choke has
enough Q (for low power TX or receiving applications it only requires modest
Q) and low enough dc resistance, it will work fine. I have passed dc to
control relays though the binocular core 2 or 4 turn windings without any
measurable or noticeable ill effects, but it is generally best to measure
the system on the test bench.

> Several remote circuits even suggest values up to 2.5 mH.

That's a pretty big choke for 160m or even standard BCB. I've found several
that do maintain high impedance without series-resonances over all of HF,
but it is also easy to find poor chokes! I would also measure the choke
first, or depend on a reliable source for good information as to impedance.

In manufacturing it is common to run into choke impedance and Q problems
when component manufacturers change materials or purchasing agents sourced
new chokes with the same published ratings!

As a general rule we are better off using minimum inductance possible, and
not needlessly "oversize" choke inductance.

73 Tom