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Re: [Amps] B&W FC-30 Filament Choke: EPILOGUE

To: "EP Swynar" <gswynar@durham.net>, <topband@contesting.com>,<amps@contesting.com>
Subject: Re: [Amps] B&W FC-30 Filament Choke: EPILOGUE
From: "Dan Hearn" <dhearn@air-pipe.com>
Date: Sun, 4 Mar 2007 06:30:35 -0800
List-post: <mailto:amps@contesting.com>
Eddy, I recall an article in QST many years ago about TVI elimination in
which fly back TV cores were used. I believe there was a comment that these
cores are low frequency jobs and, in the TVI function, are operated well
above their normal frequency range. I believe the article said that the
impedance created in the hf range is primarily resistive rather than
inductive and  they would be very poor candidates for a filament choke. 73,
Dan, N5AR

-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of EP Swynar
Sent: Sunday, March 04, 2007 4:56 AM
To: topband@contesting.com; amps@contesting.com
Subject: [Amps] B&W FC-30 Filament Choke: EPILOGUE


Good Morning All...

...And many thanks to the SEVEN respondents who took the time to address my
query yesterday re. the whys & wherefores of my old Barker & Williamson type
"FC-30" filament choke...

For benefit of any interested parties who may one day chance across one of
these assemblies at a Hamfest, etc., here's what I learned on the PLUS side
(file it away on the back-burner --- it may prove to be useful at some
time):

-The FC-30 is, in essence, TWO type FC-15 filament chokes in ONE enclosure;

-Each of these FC-15 chokes is rated at 15-amperes: to safely pass
30-amperes through them, you simply parallel the two, and,

-The unit has the flexibility of feeding two separate tubes from two
separate filament transformers via its two separate chokes (maximum
15-amperes per filament, of course), or, one tube / paralleled tubes
requiring 30-amperes maximum.

Now, on the MINUS side:

-The FC-30 is specified for operation from 3.5-MHz to 30-MHz, inclusive:
because each FC-15 rod is only 3-1/2" long, it does not have enough
inductance for 160-meters;

-Even if I elected to SERIES-connect the two interior FC-15's to secure
twice the inductance for possible use on Topband, I would be robbing it of
its ability to handle 30-amperes of filament current...and my hoped-for
4-1000A requires 21-amperes to make it glow (sigh!).

I've always been curious as to the possible effectiveness of employing the
ferrite core from a TV picture tube deflection yoke / coil assembly as the
foundation for a robust torroid-type filament choke...I have an inordinately
LARGE example of one here, which was removed from a junked early colour TV
set many years ago: maybe this is an opportunity in disguise, waiting to be
realized...

I have no knowledge of anyone ever having tried this latter trick, but I
can't see why it wouldn't work.

~73~ Eddy VE3CUI - VE3XZ
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