[TowerTalk] Fwd: Fair rite materials for choke baluns

[Hans Hammarquist]

I have to answer you here, Earl:" I'm using a Windom/Longwire antenna. I can tune that to 160m - 10m easy. I can even load it up on 6m although I'm still waiting for a QSO there."


As I am "balancing" my feed line, or more correctly, am reducing the RF in my shack by putting a choke between the tuner and the radio (the "output" that is the end facing the TRX is well grounded for further reduction of RF in the shack) I am depending on maximum available Z in the choke all the way from 1.8 MHz to 29.7 MHz.


I am presently relying on a choke made of 50 feet of RG58 wound on a 4 inch PVC pipe. I am using a variable pits to avoid a specific resonance and thereby achieving a reasonably wideband, high Z. The choke is about 12 inch long.


Hans - N2JFS



-----Original Message-----
From: Earl Morse <kz8e at wt.net>
To: towertalk <towertalk at contesting.com>
Sent: Sun, Jul 3, 2016 8:54 pm
Subject: Re: [TowerTalk] Fair rite materials for choke baluns


.....e nice teflon sleeving and Thermaleze wire to make them with.  

Wide band, high power transmission line transformers are difficult to make.  I would highly suggest limiting the design to the antenna at hand, I mean how often are you going to move your 1.8 MHz transformer over to your 28 MHz yagi?  It will certainly make the design a lot easier to realize.

Earl
N8SS

  
> _______________________________________________


You seem to be seeking the "holy grail" of a universal
choke covering 160 to 10 meters.  I don't know of
any antenna that covers 160 to 10 meters, so why
do we need a choke that does that?  So my opinion is
that is doesn't make sense to do that.  It would
be better to simply use the optimum ferrite material
for the particular band(s) that the choke is to be
used for.

A place where there actually is a need for a 160 to
10 meters (or even 6 meters) choke is in solid
state amplifier design, for the DC feed choke.  I
studied this problem extensively a few years ago
looking at all Fair-Rite materials, pretending I
could get any shape, etc.  I even made some measurements
to fill in gaps in the Fair-Rite data sheets.  After
all that, the winner was ... boring old 43 material.
Luckily, this is probably the most available material.
Even a lot of competitors make their own version.
However, I found that the imitations were markedly
inferior to Fair-Rite 43 in this particular application.
They would probably be fine for general purpose RFI
fixing.

Rick N6RK


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