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Author Topic: Does this pass the sanity test?  (Read 1988 times)
NR6K
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Posts: 51




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« on: July 05, 2010, 09:40:15 AM »

I have been considering a flagpole antenna until I came up with this idea.
I have a large metal awning around 3/4 of my house. I am thinking of putting a High Sierra Sidekick with a mag mount on one of the awnings where it can not be seen from the street. Does this pass the sanity test?
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WB6BYU
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Posts: 12792




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« Reply #1 on: July 05, 2010, 10:45:43 AM »

The mag mount part doesn't pass.  (Especially if the awning is aluminum.)  A mag mount
just doesn't have enough coupling for HF.  But if you can build a sturdy mount and make
good contact to the metal awning roof (which may require putting a sheet metal screw
through each corner where the panels meet) then it should work about as well as you
can expect for a very short vertical radiator.
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WX7G
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Posts: 5710




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« Reply #2 on: July 05, 2010, 11:16:48 AM »

Connect the mag mount GND to the awning with a wire and sheet metal screw. The awning might not provide a low impedance counterpoise. So, add a 1:1 balun at the feedpoint to reduce coax shield current. The screwdriver, along with a tuner or autotuner at the shack should do the job.

I use a Tarheel 200HP screwdriver ground mounted with 60, 20' radials. 500 watts CW works the world on 160-10 meters.
« Last Edit: July 05, 2010, 11:18:19 AM by DAVE CUTHBERT » Logged
AF6WI
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Posts: 105


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« Reply #3 on: July 05, 2010, 11:26:48 AM »

Your antenna may be directional. I use a Tarheel screwdriver style antenna on my van, mounted over one of the rear wheels, and the antenna is directional toward the front of the van.

If you can get good radials on your flagpole, that _probably_ would be a better antenna, but it's hard to guess without knowing more about the awning, direction, height, and such. Cost is a factor, of course, so you get to make your judgment.
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W5LZ
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Posts: 459




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« Reply #4 on: July 08, 2010, 02:46:15 AM »

There -may- be a lot of things that you'd have to 'correct' for by doing it this way.  But, what's so unusual about that?  I'd certainly think about it, it's an option!  I would expect about the same 'performance' as I would with that antenna on a vehicle.  Not going to be the best by any means, but certainly usable.
Paul
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KQ6Q
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Posts: 951




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« Reply #5 on: July 17, 2010, 09:09:25 PM »

Since your awning is aluminum, mag mount is no go. Do get a mount which will let you support your screwdriver antenna on a section of mast - TV mast brackets on the side of the house, with the mast protruding enough above the awning for the mount. Run some radials - one or two for each band - out and around the awnings. Connect the ground side of the antenna mount to the awning surfaces with star washers. You'll have some effect from the radials, some from the awnings, and the awnings WILL reflect the RF nicely - particularly if the main roof doesn't go much above them. You could also try the concept inexpensively - the same mount, but get a hamstick for your favorite band, and try it this way.
I'm 'lucky' - have a 1968 double wide mobilehome with a steel roof, so I do use mag-mounts - triple magmounts - one with multi-resonators for 20-10m, and singles for 80 and 160, with a Stepdown transformer for impedance match. On forty meters, I couldn't work NoCal from SoCal, so I went with a hamstick dipole on a mast at one end of the house - work short and long skip nicely with it.
You don't do QRP with this - I use 100W, and get out decently with the reduced efficiency antennas.

Fred, KQ6Q
« Last Edit: August 01, 2010, 09:18:53 PM by KQ6Q » Logged
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