[TowerTalk] RG-304 for CMC ?

[Jim Thomson]

Date: Sun, 24 Apr 2016 17:14:14 -0400
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk at tm.net>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] RG-304 for CMC ?

What's the difference between using LMR-400, or BuryFlex with six 12" 
dia Loops equally spaced, compared to bundling the same size loops into 
a single bunch
or for that matter, grouping any coax together rather than equally 
spaced loops?
It'd lower the resonant frequency, but other than that (and looking 
neater), what about the choke's characteristics?
Would it narrow the range of high impedance?  Lower, raise, or leave the 
maximum impedance unaffected?

73

Roger (K8RI)

##  Bunched up loops  lowers  res freq.   Depending on choke  config, it can
narrow the range of the choke, to the point where it covers 80m  with high  5-6 k RS... but not 40m. 
Lousy on 40m, like 650 ohms.    This appears to be the case  when  Binoc 
config is used in some cases.   With binoc config, with torroids at the 9 +
3  oclock positions, the turns all end up bunched  together for the entire loops. 
Bad news  if  LMR-400 /213-U /393  coax used.   A LOT more C  between turns
with the .405 OD cables...vs  58-U / 303 etc.  

##  One  advantage to binoc config, is you can then wind in 1/2 turn increments, like
4 -  4.5 – 5  - 5.5  etc. 

## 12 inch diam loops is a trick to maintain spacing between each loop.   With loops
equally spaced around the cores, now you end up with a mess that is almost 2 foot in diameter,
which is exactly what I dont want for a cmc...esp on a 80m rotary dipole, mounted 10 ft up
the mast.     8.5 K in a little box, on 80m, with the CMC-230-5K is a more elegant solution.  

## 12 inch diam loop = 3 ft in circumference.  7 turns = 21 ft of  LMR-400..which is a lotta 
weight,bulk,windload, etc.  But it does provide outstanding high Z / RS  across 80+ 40m..and
160m.

Jim   VE7RF