----- Original Message -----
From: "Dan" <w0vd@sofnet.com>
Subject: Topband: FERRITE BEADS
> I need to build a good current balun for 80 and 160 meters.
Getting significant common mode suppression on 160 meters with split
blocks or "beads" for RG8 size coax is rather expensive unless you
just happen to have a private stock.
Try 76" of RG-400/U and a T300A-2 powdered iron toroid. That will give
you big-momma suppression.
RG400 is teflon/teflon/double shield/silvered copper coax the same
diameter as RG58 that will easily handle max amateur levels.
76" of RG400 will give you 17 or 18 turns that will occupy 3/4 of the
toroid diameter and leave enough room for PL259/UG175 on the ends.
Also nice to not worry about melting the coax when you solder the
connectors.
If you are interested, I will supply construction details of one of
these that we have on the DE of an 80M wire yagi, where the *known*
length of RG400 is part of a 50/72 ohm series matching transformer for
the 25 ohm feed impedance.
73, Guy
K2AV
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