[Amps] Drake L4B to 6 Meters Help

[Jim Thomson]

Date: Mon, 12 Dec 2016 12:32:09 -0600
From: Ed Stallman <ed.n5dg at gmail.com>
To: amps at 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