Date: Fri, 17 Feb 2017 01:16:01 -0500
From: "Bert Almemo" <balmemo@sympatico.ca>
To: <john@kk9a.com>, <towertalk@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
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