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Topband: Delta RX Antenna - Part 2

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Subject: Topband: Delta RX Antenna - Part 2
From: (Larry Molitor)
Date: Mon, 27 Nov 2000 21:15:33 -0100
Here is an update on the ongoing ground-independent RX antenna work I've 
been doing.

First of all, let me thank those who responded to my request for info on 
the "Delta" configuration. The inputs were very helpful.

To summarize, I wanted to try phasing a couple of RX antennas in order to 
help with my local noise problem. The "Delta" configuration as used by 
FO0AAA was selected because of it's economical use of resources: wire, 
support structure, and real estate.

Unfortunately, the saying "There ain't no free lunch" was once more proven. 
The "Delta" turned out to be very much more susceptible to degradation 
caused by nearby objects, such as other antennas, metal buildings, and wire 
fences, that either a "Flag" or a "Pennant". Mounted in the same spot, 
using the same reference signal, the pennant and flag were effected almost 
an order of magnitude less than the delta was. No amount of fiddling with 
feed line beads and isolation transformers helped. The beads would 
sometimes help with the delta but not in every location or direction tried.

I'm going to stick my neck out here and suggest that this effect is caused 
by the delta lacking symmetry. That is, if you draw a line from the feed 
point to the termination, the antenna is not a mirror image above and below 
the line as the flag and pennant configurations are. Opinions?

After many hours of testing the delta, the pennant, and the flag 
configurations, I'm forced to drop the delta from any consideration for use 
at my QTH. I will be conducting more tests using flags and pennants in 
single and phased configurations.

Early results with phasing (using MFJ1026) were dismal. I was not able to 
improve the S/N in the forward direction at all. I was able to null out 
some stuff off the sides nicely, but NOT my power line noise. Off reflector 
suggestions and discussions welcome.


Larry - W7IUV

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