tower shunt feed for 160m
 

Greetings,

The ON4UN book has a good section on this subject. Nice charts and graphs to
get an idea of where to find the best feed point etc. Unfortunately he
doesn't discuss the effect of tower guy wires.

My tower, 110 ft Rohn 25G with 5 sets of guys. The guy wires are
un-insulated and grounded at bottom using braid and ground rod. The top set
of wires are of course about 120 ft long each. Have Force 12 C-4S on top
with 10 ft of mast; about 4 ft extra mast above beam - poor planning on my
part. :)

Any hints on how to model this? Easiest app to use for this etc would also
be appreciated.

I've been told one can use an antenna analyzer, like mfj 259b, to find match
point. Is a good way?

Thanks,
Jim - ku5s
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email sent to:
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Sorry for any inconvenience.

Why not model it exactly how it is? Plot the coordinates,
of the elements, crank the 'knob' and see what comes out. Can
you use an antenna analyzer? I would think that you could.
'Doc

On Sat, 3 Jan 2004 15:00:30 -0600, "J Tabor"
wrote:

Greetings,

The ON4UN book has a good section on this subject. Nice charts and graphs to
get an idea of where to find the best feed point etc. Unfortunately he
doesn't discuss the effect of tower guy wires.

My tower, 110 ft Rohn 25G with 5 sets of guys. The guy wires are
un-insulated and grounded at bottom using braid and ground rod. The top set
of wires are of course about 120 ft long each. Have Force 12 C-4S on top
with 10 ft of mast; about 4 ft extra mast above beam - poor planning on my
part. :)

Any hints on how to model this? Easiest app to use for this etc would also
be appreciated.

I've been told one can use an antenna analyzer, like mfj 259b, to find match
point. Is a good way?

Thanks,
Jim - ku5s

Hi Jim,

I've modeled smaller towers than this that would load up to 160M. It
conforms to NORDs or NOLs except in one significant respect: the
conductive guys. However, I have modeled along that line too, but
just with one set of guys.

To model it as you describe, build it with a conductive wire
completing the guy anchors back to the tower (as this is how the NORDs
or NOLs are implemented). I don't think a gamma match should elevate
above the first set of guys.

My guess is that it is going to resonate at a very low frequency, well
below 160M. But that would simply be the first resonance. The
overall height will dominate the pattern and elevation lobes.

73's
Richard Clark, KB7QHC

Hi,

Thanks very much for the reply.

Jim - ku5s
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Sorry for any inconvenience.

Howdy,

Thanks for the reply. I can of course aquire antenna analyzer and study
instructions. G

Regards,
Jim
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email sent to:
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Sorry for any inconvenience.
"'Doc" wrote in message ...
Why not model it exactly how it is? Plot the coordinates,
of the elements, crank the 'knob' and see what comes out. Can
you use an antenna analyzer? I would think that you could.
'Doc