Topband: Delta RX antenna

[Larry Molitor]

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


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