I have some OLD FC-30 chokes in metal boxes with 4 terminals on each end.
One had a bad internal connection so I pried open the box and found that it
was made of ferrite or powdered iron toroids not ferrite sticks.
73
Bill wa4lav
At 10:52 AM 3/4/2007 -0600, Robert B. Bonner wrote:
>Eddy, get an FC-25 from RF parts or Surplus sales of Nebraska. They are
>like $35
>
>-----Original Message-----
>From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>Behalf Of EP Swynar
>Sent: Sunday, March 04, 2007 6:56 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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