Topband: Air Wound Coil

[Jim Thomson]

-----Original Message----- 
From: Richard (Rick) Karlquist
Sent: Thursday, August 30, 2018 5:44 PM
To: Guy Olinger K2AV ; Jim Thomson
Cc: TopBand List
Subject: Re: Topband: Air Wound Coil



On 8/30/2018 3:44 PM, Guy Olinger K2AV wrote:

> You can also get the edge-wound (flat) 1/4 inch by 1/16 inch coil that 
> they
> use in the ATR-30 rotary coil tuner. That's a killer piece of copper.
>

<Actually no.  Edge wound is inferior in terms of Q to round wire.
It only makes sense for a rotary coil, where it needs to be edge
wound for mechanical reasons.  On a flat strip, the current
crowds to the two edges for the same reasons that cause skin
effect, thereby wasting most of the copper.  Round wires are
immune from this because they have no edges.

73
Rick N6RK

##  Are you sure about this ?   I have used  .25 edge wound rollers, with a 
pair  of
wheels riding on the top, outer edge...  but these types used a real heavy 
duty spring
that pushed down hard on the pair of pulleys.   Have also used  .375 edge 
wound rollers,
where their is a pair of  large gold plated contacts  riding on the .375 
sides.

##  I just saw some edge wound  fixed  coils, in both .375 and also  .500 
at  a friends
place last weekend. They used clips to slide over, and pinch the sides... to 
make the tap.
Those came from a AM broadcast ant phasing setup.

##  On the edge wound rollers, that pinch both sides.. they appear to be the 
least problematic.

##  I have also tried winding  strap coils  flat, like what you used to see 
for a 10M  tank coil.
That works superb for LOW amounts of uh.   Then you can also minimize the 
spacing between
adjacent turns.   Typ used on 12-10-6m linear amp tank coils..and sometimes 
15m.   .375 strap =
.285  tubing.    .5 strap =  .364  tubing.    .75 strap =  .523  tubing, 
etc, etc.   Also used on lower
bands, like  40-6m, when making a step down  L network for  stacking  2-3 
mono band yagis.
HEC caps  from  50 ohm input to ground, then the series strap coil.... to 
the  25 / 16.66 ohm output.


##  I have had nothing but grief  with tubing coils used in roller 
inductors.  They all have the same issue,
the  single pulley that rides either on top, or on the underside  of the 
tubing... has to have a slightly oversized  hole
in the center of the pulley.  Pulley rides back and forth on a straight 
shaft.  Meanwhile the turns of the tubing coil
are spiral  wound, like the threads  on a bolt..at a slight angle  to the 
straight shaft.   Slop develops in the center hole
of the pulley, then you lose it .

Jim   VE7RF