-----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
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