[Elecraft] Balun Questions

[Gary Hinson]

1:1 baluns are dead easy to make: simply wind a few turns of the antenna end
of your coax feeder around a suitable toroid core before connecting it to
your balanced antenna.  I use the FT241 cores from Amidon Associates, the
"k" type for 160-40m bands or "61" mix for the higher HF bands.  I can
easily get 10 turns of RG58 coax on a core, and these seem to work nicely
for me [I don't have the knowledge, test gear or patience to test them on
the bench, but depend on Mr Sevick's advice in his book.]  I've had no
problems running our legal limit of 500W into these.

4:1 baluns require a just bit more work.  These are made by winding a
bifilar coil using two tightly-strapped wires of the appropriate size and
type on a suitable core - a chunky T400A2 powdered iron core in my QRO balun
(capable of well over the legal limit I'm sure), with an SO239 connector for
the coax.  

All my baluns use watertight plastic boxes with rubber gaskets to seal their
lids, stainless-steel hardware for the antenna connections (S/S wing nuts
make them much easier to connect up antennas in the field), and some care to
ensure they remain watertight in use (e.g. I use superglue to wick into the
gaps and seal both SO239s and antenna connections to the case, plus
self-amalgamating rubber tape on any PL259-SO239 connections with a layer of
ordinary electrical tape over the outside to cut down UV damage to the
rubber).

For LF dipoles that will put a lot of stress on the center connections, I
use an army-surplus ceramic open wire feeder spreader for strain relief on
the antenna wire, using tie-wraps to hold the spreader to the box through
the box corner mounting holes which don't penetrate the sealed section, at
least in the boxes I can buy here.

Even buying everything new and importing the cores from the US, they are
*much* cheaper than any commercial units of similar power-handling capacity
that I can obtain, here in ZL anyway.  As a very happy customer, I have no
hesitation in recommending Amidon  www.AmidonCorp.com

There are photos etc. on my site at
http://www.g4ifb.com/html/homebrew.html#Baluns and I'd be happy to answer
any queries as best I can.

73,
Gary  ZL2iFB