Scott Francois wrote:
> THANKS FOR ALL REPLIES AHEAD OF TIME. MY NAME IS SCOTT-W9SF.
> HERE IS MY QUESTION:
> KT34XA AT 90FT.
> ANOTHER KT34XA 33FT. DOWN ON THE TOWER (57FT FROM GROUND)
> DUNESTAR WX0B STACK MATCH
> BOTH POINTED AT EU
> I DID SOME SIGNAL REPORTS IN TO EU ON 20MTRS. AND WAS NOT REAL HAPPY WITH
> THE FINDINGS. THE HIGH BEAM ALWAYS HAD A MIN. OF 1-2 S UNITS BETTER SIGNAL
> THE TWO OF THE STACKED. SAME FINGINGS ON 15MTRS.
> NOW TWO OF THE GUY WIRES ARE CLOSE THE THE FRONT END OF THE LOW BEAM.
> THE GUYS ARE INSULATED FROM TOWER.
> ANY IDEAS? I HAVE NEVER STACKED BEFORE AND NOT SURE WHAT TO EXPECT BUT I
> DID EXPECT THE STACK TO HAVE A BETTER SIGNAL THAN THE HIGH BEAM.
> THANKS AGN DE W9SF SCOTT (NORTHERN BLACK HOLE)
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Scott, there are more variables than what you mentioned in your
message. But, you
have all the information and capability to answer your own question as
well. The answer to your question can be readily answered by modelling
your stack on a computer using any of a variety of modelling programs:
EZNEC, ELNEC, YO, etc..That will give you a precise answer.
A couple of things though: The stack will have a higher angle of
radiation than the top antenna alone. Therefore, if the signals from
Europe, AT THE TIME YOU MADE YOUR MEASURMENTS, were coming in at the low
angle (more compatable with the top antenna) then it is not surprising
that the top beam would have a better signal.
However, I'd say that the two antennas are too close together. Better
stacking distance would put the lower one 1/2 way between the ground and
the top beam. Model this and see what you get.
As far as metal guy wire interaction is concerned, yes that could also
be a factor. Insulating the guy from the tower (you don't say how you
did this) will not necessarily help. It depends on how you did it:
fiberglass rod (how long?); insulator at the tower?, etc. Unless you
used nearly full length Phillistran or fiberglass guy rod (as I and
several others do), or broke up the guy wires with insulators no less
than every 11-12 feet (for the 80-10 M contest bands, per the ARRL
Handbook), you will have some interaction. However, again this can be
modelled very easily and you will know what any interaction has on your
Bottom line: model it!!
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