Date: Mon, 12 Dec 2016 12:32:09 -0600
From: Ed Stallman <ed.n5dg@gmail.com>
To: amps@contesting.com
Subject: Re: [Amps] Drake L4B to 6 Meters Help
## .25 inch OD tubing has the same aprx circumference as .375 inch wide
strap. Strap conducts RF on
BOTH sides. Tubing only conducts RF on the outside of the tubing. .5 inch
wide strap = .318 inch OD tubing.
Again, strap, wound flat, has no stray C between adjacent turns. Easy to wind
flat strap coils vs tubing coils,
+ overall diam is reduced greatly.
Where can one find the .5 inch wide strap = .318 inch OD ? Maybe McMaster Carr
? I've seen some hammer the 1/4 copper tubing flat but it looked tacky
Ed
### my local metal shop has 3 ft x 7 ft sheets of cu in thickness from .015
up to .125 thick. I just get them to shear it for me in 3 ft lengths..in any
width I want.
Typ aprx .029 to .040 thickness works good. You want it thick enough to work
with. Too thin and holes deform... like shim stock, typ .005 to .010 thick.
## I also saw rolls of cu strap at local home depot, but that was a while
back. I think georgia copper also still sells cu strap. Its easy to cut with
tin snips, and easy to
punch holes with my roper whitney hand punch. So if u can get it in say 1
inch wide... easy to cut down the middle to .5 inch wide.
## I was lucky local shop had sheets of it. Then I get em to shear it for me
typ in .5 inch....75 inch and 1 inch. The .75 cut in half becomes .375 inch.
## I silver plate with the cool-amp glop from ore. I wound the pair of
40m coils in my f12 340N nema box with 1 inch wide cu strap on a 1.5 inch ID
with aprx
4.5 turns. Then silver plated em. 4 x SPDT gigavac g2 ceramic vac relays used
to change taps, 2 relays per coil. Then it ends up with 4 x segments = flat
swr across the band.
1 inch wide strap = .637 inch diam tubing.
## .375 inch wide strap is also easy to cut down to a point at one end... for
insertion into a small bandswitch, like what I used on my hb PI tuned inputs.
Which is just a 4 uh coil,
made from 17 turns of 6 ga solid cu wire on a 1.5 inch ID. Then tapped for
the various HF bands. Broadcast variable on each side..each with a 6:1
jackson bros ball drive.
Flat input swr on each band. Just dial it up by the numbers. The ball drives
are calibrated 0-100 across a 180 deg arc..on the skirt.
## Phone around. Some metal shops carry cu strap, and also rolls and also
sheets.
Jim VE7RF
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