Topband: K1FZ Beverage Transformers

[John Kaufmann]

At 10:59 PM 10/27/99 -0500, Merv Schweigert wrote:

>Have the same problem here with a coaxial 850 foot beverage I just
>put up.. it has unequal signal levels, off the "back" is noticably down
>compared to the front.
 
I would suggest trying a reflection transformer at the end of the Beverage.
Connecting one the Beverage wires directly to ground generally results in
an impedance mismatch between the "antenna" mode and the "transmission
line" mode of the 2-wire Beverage.  A reflection transfomer matches the two
modes and you will probably see increased signal levels in the reverse
direction and also better F/B in the forward direction.  This is all
explained in more detail in ON4UN's new book (see page 7-22).

A procedure I use for "tweaking" the reflection transformer is to adjust
the turns ratio until the SWR in the reverse direction at the receiver end
is flattest.  By flattest I mean that SWR exhibits the smallest variations
up and down over a wide range of frequencies, and not necessarily the
lowest SWR.  With an antenna analyzer like the AEA or MFJ, sweep the
frequency from 1.8 to as high as 10 MHz and look for the SWR to change the
least over this entire range, not just inside the amateur bands.  This
procedure usually gets you very close to the optimum.

73, John W1FV



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