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Author Topic: Antenna Spacing  (Read 756 times)
W5CPT
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Posts: 561




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« on: August 07, 2006, 01:16:30 PM »

Other than "As far apart as possible." is there a general rule on antenna spacing.  That is "How far from the tower should the multiband vertical be and how far from the Dipole should the tower be?

The Tower, Dipole and the vertical will share bands,

Tennadyne LP on tower with 10, 12, 15, 17 & 20 ...  

The vertical HF9V with all that and 6, 40 & 80 ...

The dipole a 40 & 80 trapped affair.

The yard is large but too much seperation means lots of coax and while I have lots of coax I prefer to keep runs & losses low.  And just to make things interesting I have a pond about 200' from the coax panel, making the idea of a water mounted vertical a possiblility.

Any ideas???


Clint W5CPT
btw - I can supply rudimentry drawings by email if someone really wants to analyze this ----
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WB2WIK
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Posts: 20666




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« Reply #1 on: August 07, 2006, 03:47:32 PM »

>Antenna Spacing       Reply
by W5CPT on August 7, 2006    Mail this to a friend!
The Tower, Dipole and the vertical will share bands,
Tennadyne LP on tower with 10, 12, 15, 17 & 20 ...
The vertical HF9V with all that and 6, 40 & 80 ...
The dipole a 40 & 80 trapped affair.<

::Unless you have a way to get both ends of the 40/80m dipole higher than your tower is, I'd use the tower as a center support for a 40/80m inverted vee by installing the feedpoint of this dipole just below the top of the tower.  Sloping 40/80m elements will not interact with the T6 at all.  Mine certainly doesn't and this is exactly how I have my T6 and 40/80m dipole installed.

>The yard is large but too much seperation means lots of coax and while I have lots of coax I prefer to keep runs & losses low.<

::I wouldn't worry about coax loss at such low frequencies -- it's inconsequential.  My T6 feedline is 180' and my 40/80m inverted vee feedline is 170 feet and those are both so short I can hardly measure any loss in either of them.  If they were twice that long, it still wouldn't be very much.

>And just to make things interesting I have a pond about 200' from the coax panel, making the idea of a water mounted vertical a possiblility.<

::I doubt that will help anything, unless it's salt water and salted to at least seawater content.  Fresh water isn't a conductor, at least not any more of a conductor than soil is.  Either way, a vertical needs radials, and the Butternut absolutely needs radials.  I had my HF9V installed in a saltwater marsh close to the ocean at the Jersey shore when I lived there, and without copper radials, it stunk.  With radials, it worked just fine.

WB2WIK/6
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WA7NCL
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Posts: 625




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« Reply #2 on: August 08, 2006, 09:43:05 AM »

You need to buy a copy of EZ-Nec, you can model wire antenna to your hearts content.

You are worrying a little too much about antenna interaction.  I usually just put new antennas up and see how they work.  You can open and short the feedline of the new antenna while you are tansmitting on the old one and see if the SWR changes.  That can indicate interaction.  You can also look for effects in recieved signals.

If you still want to consider interaction I would use rules of thumb like keeping like polarized antennas at least 1/2 to 1 wavelength apart and mount horizontal antennas at right angles if possible.

But your best bet is an antenna analysis program.  You will also learn a lot about antennas as well.

try this web site: http://www.cebik.com/
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