[ARC5] Ceramic Beads

[Michael Hanz]

A Boeing drawing for the B-29 calls it "Wire, steel, copper-clad, type 
W-106-A, to be manufactured per spec 71-526-C."  In the materials list 
it says ".039 DIA.", which is not a standard wire gauge these days but 
is close enough to #18 to be indistinguishable.  I get mine from 
https://thewireman.com/antennap.html

I'm assuming that you are restoring the AT-21 to a specific date, as I 
have somewhere around here a directive that eliminated the ceramic beads 
from the command set antennas - I think because the danger of getting an 
RF burn from a low power set was considered minimal, and they are 
somewhat of a pain.  Once you get the lengths right, you'll need to peel 
off some tiny copper washers on the lathe to solder on the antenna 
wire.  That'll keep them together and not falling all over the flight 
deck every time you lift a wire to pull out a transmitter.

Happy beading,
Mike  KC4TOS

On 5/23/2018 10:49 PM, Craig wrote:
> Hi Mike: Thanks for the diameter info, as I couldn't remember what it 
> was. As to the number of beads, the book calls out a quantity of 450 
> of them. The AT ran a two transmitter, three receiver set up. Where 
> the extra length comes into play, is that both transmit lead are 
> routed differently to the BC-442.
>
> The next trick is finding some W-106-A antenna wire in bulk.
>
>
> Craig
>
> KF5JOT
>
> Fairchild AT-21-BA
>
>
> On 05/23/2018 05:31 PM, Michael Hanz wrote:
>> They are IN-83 beads, Craig.  From my web page on insulators 
>> (http://aafradio.org/docs/aircraft_antenna_insulators.html ):
>>
>> IN-83 is a Signal Corps designation, and is 5/16" in diameter, 48 
>> beads per foot, which is about 1/4" long nested in the next bead.
>>
>> Man, 500 seems a lot for an aircraft the size of the AT-21, but I'm 
>> sure you've done the measurements.  Even with the two ART-13's in the 
>> Enola Gay, I don't think we had more than maybe 7-8 feet. They 
>> designed the runs to get the RF out of the shack and through the 
>> fuselage as directly as possible.  I'm assuming you are just using 
>> them for the Liason transmitter.
>>
>>   Hope that helps,
>>  - Mike  KC4TOS
>>
>
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-- 
Michael Hanz - KC4TOS