Just a factoid on Formvar coating. The company I worked for in CA used a lot
of it and when it got old and you tried to bend it the Formvar coating would
crack and expose the base copper. Since we only used it in straight pieces
it was not a problem during manufacturing(Bourns Wirewound Trimpots). They
threw out a bunch of it when it got brittle. I wish I had taken more of it
home with me.
Bob W6TR
----- Original Message -----
From: "alexeban" <alexeban@gmail.com>
To: "'TMorton'" <cx7tt@4email.net>; <amps@contesting.com>
Sent: Sunday, November 16, 2008 3:00 PM
Subject: Re: [Amps] Core wrapping?
> ...first, core wrapping stems from the time when cores were unpainted.
> Indiana General were notorious!
> Second, the wrapping was done in order to avoid arcing to the core at a
> time
> when wire insulation was not at its best. Today Teflon covered or Formvar
> wire can withstand 2-3 kV quite easily.
> What remains is just protection from the abrasive corners of the cores and
> a
> little cushioning to absorb wire deformations resulting from tightening
> the
> assembly to its support. wrapping each core separately in a stack doesn't
> do
> a thing for the whole.
> Alex 4Z5KS
>
> SunWolf
> "Jesus, come get your kids, they're tearing up my Mother's backyard!"
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of TMorton
> Sent: Wednesday, November 12, 2008 7:32 PM
> To: amps@contesting.com
> Subject: [Amps] Core wrapping?
>
> Am in the process of building up a 8877 amp and now working on the Tank
> Circuit coils....I am pretty much following the ARRL Handbook 2006 for
> L4 and L3 (160,80m). to handle the high power, I am using 3x T300-2
> cores with #10 Teflon silver wire and 3x T225-2 cores w/teflon, etc. My
> question is when 'stacking' the cores do I stack the 3 cores then wrap
> the fiberglass tape around them OR do I individually wrap each of the 3
> cores with the glass tape then do an additional wrap over the 3 of them
> together?
> Tnx
> 73
> Tom
> CX7TT
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