Well, Tom
I think that 31 material is probably a good choice for cleaning RF from
wiring that isn't handling RF power and where there isn't much in the way of
shunt impedance for the choke to work against -like a line from an
electricity meter carrying a much as 480 VAC (530 VAC at 480 high-line).
That's also an issue on high-speed digital circuits that can't tolerate much
in the way of shunt capacitance.
Not so sure about it as a "balun" on coax carrying much RF power!
73
Charlie, K4OT V
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Tom W8JI
Sent: Tuesday, May 21, 2013 10:08 PM
To: topband@contesting.com
Subject: Re: Topband: Thanks!
> Well, I haven't used 31 mix material for common-mode chokes or current
> baluns, because I didn't have any - but it would be my choice. I used
> higher
> frequency material because I had plenty of it - some in substantial sizes
31 isn't a magic cure-all, just as no other single material is. One of the
most difficult things in the world is designing something that fits systems
with conflicting goals.
When power levels increase, or when systems have very high voltages
impressed across the choke, a higher Q material often works better. Tuner
baluns are an example where theoretically optimum common mode impedance is
traded off for reducing heat. If a balun melts down, it is useless.
The balun that never gets hot is a short circuit or perfect lossless
reactance. The balun that has immunity to resonance is a balun that will
melt down with certain load impedances.
The ARRL still doesn't have the issue of baluns on the inputs of tuners
correct, so we have a long way to go in public education. There was a
discussion on the Elecraft reflector where someone just got it wrong in an
analysis, and an ARRL staffer used the flawed design analysis to justify a
Handbook tuner with poor balance design.
Every system has to be looked at as a system.
73 Tom
All good topband ops know how to put up a beverage at night.
_________________
Topband Reflector
All good topband ops know how to put up a beverage at night.
_________________
Topband Reflector
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