Here's a simple balun that works well on 80/160
which requires only 100 inches of RG-8X coax. I used it
for many years in Colorado running 1.5 kW to a trapped
dipole for 80/160 with no problems. The original design
came from a Ham Radio series but I don't have the
exact reference. I recall the designer had made
measurements using an HP Network Analyzer and
the balance performance was excellent on 80/160
compared to commercial baluns.
1. Carefully remove a small ring of the coax cover at
~100" from the end.
2. Solder ~100" of wire around the braid at this point.
I recall I used #16 insulated wire.
3. Loosely wind 7 turns of the coax in one direction
(about a 6 or 7" diameter coil) and loosely wind 7
turns of the wire in the OPPOSITE direction.
4. Solder the wire to the inner conductor at the end
of the coax (after separating 2-3" of braid as a pigtail).
5. Waterproof the coax ends and the area where the
wire was attached.
6. Secure the loosely bundled coil of coax and wire
with tape or tie-wraps.
7. Attach the coax shield to one side of the antenna
and the center conductor (including attached wire)
to the other side.
Instead of using 50' of coax, this uses only
a bit over 8' and works well. Maybe someone has
the exact Ham Radio reference but I'm fairly certain
my memory of the construction is correct. If I made
a mistake, hopefully someone will correct it.
73 & Merry Christmas!
Bill W4ZV
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|