Topband: Air Wound Coil

[Jim Thomson]

-----Original Message----- 
From: Richard (Rick) Karlquist
Sent: Friday, August 31, 2018 7:13 AM
To: Jim Thomson ; Guy Olinger K2AV
Cc: TopBand List
Subject: Re: Topband: Air Wound Coil


<I am sure that flat conductors result in lower Q than round conductor.
<I have done innumerable Q meter measurements to confirm this.
<I didn't say that flat conductors don't work at all.
73
Rick N6RK


##  What are you using to measure Q ??   I did  discover one anomoly with 
coils
and Q.     XL  increases as freq  increases.  XL=  2 pi * F * L.    However, 
Q  =  XL / ESR.
ESR, due to skin effect, only increases to the sq rt of the ratio of the 
freqs involved.
IE,  10m has  double  the ESR that the same coil has on 40m.

##  A say  5 uh  coil has DOUBLE the  Q on 28 mhz... vs the same 5 uh coil 
on  7 mhz.... go figure.
However, the  same  5 uh coil  will handle  double  the RF current  on 
40m..as it will  on 10m.

##  I have 2 of these  .375  edge  wound rollers.  The 2nd one has less uh, 
but has a nice tapered pitch
at one end.   50 uh  vs  40 uh.   I strap out the excess with those clips. 
22-24 uh used on 160m.  Its all
shorted out when on 20-17-15m..as an outboard .375  tubing coil is used on 
those bands, tapped with a
modified  HV solenoid.   This is on a hb amp.  17 + 15m share the same tap.

Jim  VE7RF