Has anyone built and tested the "Delta" RX antenna promoted by K6SE for use
at FO0AAA? I am interested in performance reports from others.
The "Delta" is extremely easy to build and requires only a single support
in the center. For these reasons, I decided to build at least one for an
experiment in phasing multiple RX antennas. This is another story that I
won't go into here.
Since the "Delta" is a cousin of the Flag and Pennant RX antennas, I was
surprised when it didn't work at first. Low gain and poor F/B compared to
my Flag. Part of the problem turned out to be a bad transformer
(mis-identified core material). Even with a duplicate of the 73 material
binocular core used on the Flag, F/B was poor. After several hours of
playing with the thing, I tried putting some snap-on ferrite beads on the
transmission line near the feedpoint. With six of these EMI suppression
type beads in place the F/B came way up. While it's still not the predicted
40 dB, it's about the same as my Flag. More work to be done yet I guess.
These antennas want to work. If you have a problem with one, I suggest that
you look at these three items:
1) Physically too close to TX antenna or other structure.
2) Bad transformer design/construction.
3) Feedline common-mode issues.
Next step is to phase some of these things and see if it's worth while
doing in a relatively small area. Unfortunately, this won't get done soon
enough to help me hear the current DX operations!
73,
Larry - W7IUV
--
FAQ on WWW: http://www.contesting.com/FAQ/topband
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|