[TowerTalk] What am I missing....balun

[Jim Thomson]

Date: Fri, 17 Feb 2017 01:16:01 -0500
From: "Bert Almemo" <balmemo at sympatico.ca>
To: <john at kk9a.com>, <towertalk at contesting.com>
Subject: Re: [TowerTalk] What am I missing....balun

...and this device (choke) would give you over 30 dB attenuation from 1 to
30 MHz!! I'm definetely missing something!! How can this kind of advertising
be allowed? I'm no expert but I've made a few chokes and never managed to
accomplish this kind of choking impedance with a couple of turns of coax
through a few toroids. Can someone explain please! Thanks

Bert, VE3NR

##  Its  30 db or more of  return loss.  IE:  swr is flat across the spectrum.
The marker freq is set to 26.980 mhz.  I suspect its optimized for the
11m  QRO crowd.  It might  just be  type 43 and not type 31 cores used, dunno. 
33.13 db return loss  =   1.045 : 1 swr

##  add all the turns you want, and you still wont be able to get it to work
from 1.8 to 30 mhz. 

## Interesting to note his  10 kw cw, 20 kw pep 1.8 to 30 mhz version
uses  4 turns of 393 coax through  4 x type 31 cores.  RS is 3.2 k
from  13-28 mhz.    His 3.5-60 mhz version uses  4 turns through
just 3 cores.  On both these 2 version, the cores are all type 31.

##  I saw what some of the 11m ops use for their version of a  bead  balun.
They used 20-40 type 31 or type 43   2.4 inch OD torroid cores  slid over  .875 heliax. 
To get the .875 inch heliax or  LMR-1200DB  to work on a yagi, they mount the yagi
way up the mast, with a 3 turn loop around the mast, large diam loop, like 3-4 ft 
across, and below the yagi.   The 1.4 inch ID cores are only .5 inch thick, so they gotta
use a lot of them.  Ceases to amaze me what folks come up with.

Jim  VE7RF