[Towertalk] Tribander anomaly

[W4ZW]

I have an antenna/tower question for a change of pace.

I discovered quite by accident that 15M signals are better on my 402CD
CC 40M beam  than on either of the A4S tribanders I currently have up.

I was listening  to a pileup the other evening on 15m and realized I was
on the 402CD.  Switched to the A4S which is 12' below it and the signals
dropped a full S unit.  Wow, that's strange.  I just recently rebuilt
all the antennas that were pretty much destroyed in a tropical storm.
New aluminum, hardware and feed lines.

The 402CD is rebuilt and on a Glen Martin rooftop tower about 70' above
ground which is about 18' above sea level in my back yard.  I'm ocean
front directly on the Gulf of Mexico on the southern tip of an island
with ocean and bay in all directions except NNW.

I switched to my second A4S (not rebuilt, but one I kept in the garage
for Field Day) that is on a Rohn mast about 6' lower than the first A4S
and about 35' away  to the SSE.  Same signal level as the first A4S.
Switched back to the 402CD and the DX signals pop up out of the noise.
Does the capture area of the 402CD make that much difference?  My wire
antennas are still down so I can't compare there, but as soon as the 80M
Bob tail and the full wave delta loop are be back up I intend to explore
them as well.

SWR on both the A4S's are essentially flat 1:1.  They are super on 10
and 20 compared to the 402CD, but on 15M the 40CD2 is clearly the better
receiving antenna.    The 402CD has a 2.6:1 SWR on 15M and is easily
loaded with the auto-tuner on the FT-1000D.  Of course it loads pretty
well on 12M and 17M as well.  Maybe the 402CD should be called a
quadbander, hi!

Any ideas?


Jon Hamlet,  W4ZW
Casey Key Island, FL

"A little bit of Paradise in the Gulf of Mexico"