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Multiple wire antennas

Oct 15th 2013, 23:42


Joined: Mar 22nd 2011, 04:10
Total Topics: 0
Total Posts: 0
I have a couple of questions regarding the installation of two wire antennas. Antenna 1 is an Alpha Delta DX-LB + good for operation from 160 - 10m is coax fed (LMR-400) and will be installed as an inverted V in an east-west orientation @ 30' x 60' x 30'. On each end pipe I will have a 10 - 17m vertical (Solarcon IMAX 200) and a Diamond 2/440 ground plane. I have these figured out...but wanted to provide some detail as to my anticipated layout.

Things were fine until a fellow club member presented me with a free, nearly brand new 80 - 6 OCF Dipole that he swears is a DX beast. He recently moved and his lot will not permit a 132' long wire... I however live on a farm, on a prairie, very near the Gulf coast with room for a football stadium.

I am thinking of installing the OCFD in a north-south orientation thus keeping the two antennas @ 90 degree angles to one another.

Both will be coax fed (LMR-400). How much separation vertically do I need to provide to reduce unwanted interference? Ditto the feed lines... I will be running 100 watts out to the antennas as that is what I am blessed with and think it is all I need anyway until I spend a few years learning the (HF) ropes. Should I just pass on the OCFD and save it for a rainy day?

Thanks for your time and consideration. I went all through the many books I have accumulated and cannot find an answer to using multiple wire antenna do's and don'ts.

Best regards,
Scott Long
Oct 16th 2013, 14:25


Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Antennas such as these are sufficiently complex that it isn't worth the effort to model them on a computer--you are usually better off just putting them up and seeing if they work acceptably for your needs.

It takes a lot of work to model traps and full antenna models using feedlines--possible--but too much work for most hams to use the computer.

Sometimes you can get away with very closely spaced antennas, sometimes you can't. I'm in the process of putting up a 160M inverted L in the same maple tree that supports an 40M dipole and an 80M vertical--preliminary testing indicates good performance with all three antennas.

If it doesn't work, some hams do find simplified antenna models helpful in understanding why, but this is very difficult without a good basic knowledge of antenna theory. Computers just analyze test cases--they don't offer guidance on what you should do. A solid background in antenna theory is very helpful in formulating a strategy for solving interaction issues.

Zack Lau W1VT
ARRL Senior Lab Engineer
Oct 17th 2013, 22:53


Joined: Mar 22nd 2011, 04:10
Total Topics: 0
Total Posts: 0
Thank you Zack, I cannot imagine a better reply than yours so I will go with your suggestion. I did not add that I am expecting the delivery of an MFJ 259 with all available accessories. I was hoping to avoid any obvious issues as I am going to be doing this work short handed thus the trial and error portion many hams can employ I cannot due to my far removed operating qth. I truly live in a small community, am far from family etc. etc. Thus I will go with a 10] length of fiberglass mast to separate the two antennas and see how that tests.
Thank you again kind sir for your response!

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