Hi All, is there no possibility of having the input matching network
resonate with the FC30 filament choke to allow 160m operation?
With the low impedances present it seems that the loaded Q would still be
fairly low. Seems that the rf related currents would be much lower than the
filament currents in the choke.
What parameter actually establishes the lower frequency rating of choke like
this?
Not suggesting using it this way; just wondering.
73,
Gerald K5GW
In a message dated 3/4/2007 6:57:38 A.M. Central Standard Time,
gswynar@durham.net writes:
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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