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Author Topic: Feeding an inverted L  (Read 3878 times)
KF4LXB
Member

Posts: 36




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« on: November 27, 2012, 05:49:50 AM »

Greetings all,

I am currently working on setting up my home QTH to run all QRP and have decided on an inverted L arrangement for the antenna. In my research I have decided that this will be the best possible setup for stealth operations in my restricted neighborhood. The vertical leg is made of white 22 gauge wire to match the trim on the house and the horizontal leg is made of the same wire only in black. This will be run to a tree in the front yard and I think it will be all but invisible to most prying eyes. The antenna is fed by 300 ohm TV style twin-lead. My question concerns the matter of running the feedline into the shack. I have read that twin-lead is fairly sensitive to contact with window frames and I wonder if it would be a bad idea to simply run the line through the window and close the window on top of it. As I see it I have a few option and any input would be greatly appreciated.

1) Do as I just said and run the feedline through the window (10-15 ft run for the feedline).

2) Run the feedline up through the eave of the roof into the attic and use an existing hole in the closet ceiling to get it into the shack (30-40 ft run).

3) Add a piece of wood to close the window on and pass the feedline through a hole drilled into the wood. This is my least favorite of the ideas because it would require painting the wood to match the window frame and doing the same thing for the adjoining window so that they look even (same run as #1).

Also, in my grand plan (should it come to fruition) I would be running a maximum of 10w on SSB. An attic antenna is out of the question for me because I currently use one for QRO operations and my goal is to get one outside of the house. Thank you in advance for the help.

72,
Christian KF4LXB

P.S If this is a topic better suited for the "antenna" forum I understand and it can be moved.
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Christian
Albemarle, NC
EM95
http://kf4lxb.blogspot.com
WX7G
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Posts: 6041




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« Reply #1 on: November 27, 2012, 12:03:31 PM »

I have used 300 ohm TV twin lead many times and it doesn't care if you slam the window on it. Yes in a metal window frame the twin lead impedance will dip but so what?
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KF4LXB
Member

Posts: 36




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« Reply #2 on: November 27, 2012, 06:04:12 PM »

Awesome! Thanks WX7G, I may end up going that route. It would certainly simplify the installation.
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Christian
Albemarle, NC
EM95
http://kf4lxb.blogspot.com
WX7G
Member

Posts: 6041




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« Reply #3 on: November 27, 2012, 06:44:56 PM »

The real flimsy white twin lead Radio ShackTM used to sell was great for closing in windows. The thicker brown stuff isn't as pliable but a good slamming in the window makes it fit. The last time I saw the flimsy stuff was a couple years ago at Fries Electronics in California.
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WB6BYU
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Posts: 13243




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« Reply #4 on: November 27, 2012, 07:12:10 PM »

My first HF antenna used twinlead in a metal window frame - I wrapped an old sock
around it for added insulation.   A wooden sash isn't a problem.  You can even splice
the twinlead into two thin wires (or strips of copper foil, such as that used in burglar
alarms or stained glass work), which will fit into a thinner space.

Adding some foam weatherstripping will help the window seal better.
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K1DA
Member

Posts: 500




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« Reply #5 on: December 03, 2012, 08:49:46 AM »

THe Radio Shack brown stuff will handle close to a KW without problems, I run mine through a hole in which there are  also two runs of RG 8 and a rotor cable.  The tuner matches a 100 foot long dipole with ease on 80 through 10, including 60.  I made the dipole myself, so it doesn't have a brand name Smiley .
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KF4LXB
Member

Posts: 36




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« Reply #6 on: December 03, 2012, 11:13:37 AM »

Thanks again guys for all the input. As it stands now I have finished the construction of the antenna and am waiting to install it. I may end up painting it to match the siding on the house and running it through the window or I may just run it through the eave and the attic. I think that will be a game time decision. The latter would be more stealthy but it would require more feedline. I'll let you know. Thanks again.

Christian KF4LXB
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Christian
Albemarle, NC
EM95
http://kf4lxb.blogspot.com
KU3X
Member

Posts: 142




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« Reply #7 on: January 09, 2013, 10:54:10 AM »

Did you ever think of putting a remote tuner at the base of the antenna? If you only running 200 watts or less, the MFJ 929 tuner can be placed at the base of the antenna and the DC power can be fed through the coax. You'd have to put the tuner in a weather proof enclosure, but.....MFJ does make this same model and it already comes in a weather prooof enclosure. I just forget the model number?

By doing it this way, you can run coax from the station to the tuner and the coax will ALWAYS see a low SWR.

Good luck with your project.
Barry
www.ku3x.net
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KF4LXB
Member

Posts: 36




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« Reply #8 on: January 09, 2013, 11:44:29 AM »

Barry,

That is an idea I had toyed with but the cost of remote tuners is prohibitive at this point. Hopefully, in the next week or two I will be installing the antenna. I checked with a scrap piece of the twin lead and it will shut in the window without damage to either the wire or the window so I think that is the way I will go. Plus, the window frame is some kind of plastic so it should be non-conductive. The whole run from feed point to tuner (ZM-2)should be around 10ft. I will update on any results. Thanks to all!

72,

Christian KF4LXB
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Christian
Albemarle, NC
EM95
http://kf4lxb.blogspot.com
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