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[TowerTalk] Bead Balun

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Subject: [TowerTalk] Bead Balun
From: (John Schaffner Jr.,- K8LN)
Date: Wed, 10 Nov 1999 10:56:52 -0500

The response on the BN-86 Coil Balun was great, 15 responses.  I later
decided to make my own bead balun.  Construction was simple, 50 beads on
Teflon, 50 ohm cable, weather seal and mount. The bead balun was mounted
in the old BN-86 black box with a pvc pipe housing the rest of the
length, the balun mounts perfectly to the feed straps on the TH7's beta
match.  With the unit mounted it was time for a check.  The swr curve on
10 and 20 meters checked out  identically to the measurements before.
The exception is 15 meters, the swr curve changed.

Old BN-86          Bead Balun now

21000    2.0            2.6
21100    1.5            2.1
21200    1.2            1.5
21275    1.0            1.3      1.2 at 21310 is the lowest reading
21400    1.5            1.6
21450    1.8            1.9

The leads on the bead balun are short.  I used the same meter for
measuring (Autek FR-1).   Nothing new mounted on the tower.

The Higher Power replacement from Hy-Gain (MFJ) is the BN4000,  which is
a Bead Balun.

Can anyone explain what has happen and why the only band effected was 15


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