Topband: Interesting New DX Engineering Product

[Gary Nichols]

I believe Jerry, W2FMI was responsible for the UN-UN original designs...he
was working on his first book when we visited him at his home in NJ. on our
way to New England long ago.  He sent me a pencil drawing for a 2:1 (25 ohm
to 50 ohm) UN-UN which I built and have been using for many years on my
shunt-fed-tower...de gary, kd9sv

-----Original Message-----
From: topband-bounces at contesting.com
[mailto:topband-bounces at contesting.com]On Behalf Of Jim Brown
Sent: Monday, July 26, 2004 12:02 AM
To: TopBand List; Tower Talk List
Subject: Topband: Interesting New DX Engineering Product


One of the guys in our local ham club came back from Dayton with a
very interesting new product from DX Engineering. As soon as he
showed it to me, I called up DX Engineering and bought two of them.

The product is a unun autotransformer for HF antennas designed to
transform 12.5 ohm or 25 ohm loads to 50 ohms.  This is a natural for
matching any resonant short antenna to a modern transceiver. You
must, of course, do something about the reactive component.  Opening
up the box I see good components that will handle some power and
solid, but simple construction. The website data sheet suggests that the
unit should handle 500 watts with a reasonable VSWR.

There are also several variations of hardware to add a capacity hat to a
vertical antennal.  While mobile antennas are an obvious application for
both of these products, both could also find good use in a home
antenna farm. Used in combination, I can smell more than a few dB of
improved efficiency. I think I also smell Tom Rauch's hand in the design.
It that's true, many thanks, Tom!

Jim Brown  K9YC


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