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Author Topic: Double Bazooka in attic  (Read 418 times)
N3TOZ
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Posts: 2




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« on: June 29, 2006, 11:19:25 AM »

I have recently moved into a new house and have a 64 foot long attic in which to string up a few wires. The height of the attic is about 5 to 6 feet. I have plenty of old coax from the previous owner (RG-6). If I get a long enough piece to run the length of the attic what does everybody think about taking the 300 ohm twin lead and shorting the ends and connecting it to the middle on one wire and running it in ^ fashion from the top of the attic down to the attic floor. With tuner I hope to get a decent band range.

Thanks for your time.
Nick
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WA4PTZ
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Posts: 528




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« Reply #1 on: June 29, 2006, 11:46:36 AM »

I've tried antennas in the attic and they just don't
work. I would build the antenna in the yard and
the swr would be zip but when I relocate it to the
attic it won't go below 3 to 1 swr. I have brought it
back down and set it up outside and it is perfect.
I suppose the metal framing hardware and roofing nails
must be causing it. That's all I can come up with.
73 ,
Tim
WA4PTZ
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WB2WIK
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Posts: 20612




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« Reply #2 on: June 29, 2006, 01:06:39 PM »

Not sure how your description relates to a "double bazooka."

A double bazooka dipole is normally a pair of end-shorted, horizontally opposed 1/4-wave stubs made of coax, fed in the center with coax.  Its only "advantage" over a regular 1/2-wave wire dipole is slightly wider bandwidth, and only on the band where it's resonant.  It's not a multi-band antenna.

As for antennas in attics, some work well, some don't.  It depends a lot on the attic and all the construction materials used.

WB2WIK/6
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N5UV
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Posts: 51




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« Reply #3 on: June 29, 2006, 01:22:07 PM »

I'm afraid I don't understand what kind of antenna you plan to put up, but if it's a 300 ohm twin-lead-fed dipole, in the shape of an inverted V, then you should be okay in the attic from 40m. on up...80m. will not be feasible, not unless you bend the the antenna wires and double back that length.  It's not the best way to operate an antenna, and there will be RF all over your attic and the house, but it can work for you okay so long as you have a tuner.

Now, if you are planning to make a big loop antenna or something like that, then that's a different story...most horizontal loops don't work well that close to other objects...frankly, most ants. don't at all, but you can wing it with just a plain dipole in the attic.
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WB6BYU
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Posts: 13343




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« Reply #4 on: June 29, 2006, 01:39:02 PM »

I don't understand your antenna description, either.

You have plenty of room to run an ordinary 40m dipole (even
if the ends have to be bent around a bit) as well as for
the higher bands.  You could put up such a wire and feed
it with twinlead to a tuner, but you wouldn't short the
end of the twinlead if you were to do so.  You might be
able to get it to match on 80m, but don't expect it to
be very efficient.

For 80m you would want to make the wire longer - I usually
start by running the wire diagonally to the corner then
across the end of the attic (which may add another 10
to 20 feet, depending on the shape of the house.)  Adding
a loading coil in the end sections would help bring it
closer to resonance.

If you have a lot of coax around you could use it for the
radiator, but I would NOT recommend the "double bazooka"
approach - it is really a single band design, and will
be VERY lossy on some bands.  Just short the coax at
each end and use the braid as your antenna wire, but
I'd tend to grab a spool of stranded hook-up wire instead
as it is lighter and easier to install.

If you are going to use a tuner anyway, there is little
or nothing to be gained by using a fatter wire.
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N6AJR
Member

Posts: 9910




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« Reply #5 on: June 29, 2006, 03:21:48 PM »

first off, it is better than no antenna at all,, but you will need to keep the power down and use a tuner, starting with "tv coax 9rg6) and 300 ohm you will not be good for much power. here are some ideas for som inexpensive  antennas.

http://www.ku4ay.net/dipole.html
http://www.qsl.net/kd7rem/antdipole.htm
http://www.hamuniverse.com/multidipole.html
http://www.angelfire.com/nb/ni4l/ni4ldipole.html
http://www.arrl.org/tis/info/pdf/9611073.pdf
http://www.geocities.com/n2uhc/2banddipole.html
http://www.qsl.net/na4it/fandipole.html
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KE5ICG
Member

Posts: 10




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« Reply #6 on: June 30, 2006, 10:08:34 AM »

Of course, I do not know your circumstances but you might reconsider taking it outside.  I know a guy who was using an attic ant. with so-so results (no "visible" antennas allowed in his subdivision), and another op in our area suggested he set up a big loop on the top rail of the wooden fence around his back yard. He laid the wire right on the wood securing it w/plastic cable ties and said it tunes up 10-80 just fine rain or shine.  Might be worth trying if you have a fence like that.  Or, you could always try a vertical somewhere out of sight, but outdoors.  JMHO, but I'd rather have all antennas outdoors if at all possible.  In any event, have some fun with it.  73 -- Ray KE5ICG  
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KC8VWM
Member

Posts: 3121




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« Reply #7 on: June 30, 2006, 01:25:22 PM »

Put up a dummy sattelite dish and stretch a longwire antenna to it.

The idea is to use the dish in such a manner that the antenna wire leading to the satellite dish "appears" to be the feedline for the satellite dish installation.

No, it's not an ideal antenna situation however it will at least be located outdoors and it will probobly work very well if some thought is given into the overall design.

Use things like professional looking cable TV standoffs to keep the antenna wire away from the side of the house etc..

Also keep in mind that all satellite dishes require a good ground system. Of course this would equate to the idea of an added benefit for your amateur radio antenna installation too.

Gud DX & 73

KC8VWM
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KC8VWM
Member

Posts: 3121




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« Reply #8 on: June 30, 2006, 01:34:37 PM »


Speaking of sattelite dishe installations, I once had a friend who installed a satellite dish on a fence at an antenna retricted condo.

The condo management people thought it was much better to locate the dish on the back fence than to install it directly on the building itself.

He extended a full 80 meter 1/4 wave longwire down from from the top corner of the building into free space over the back yard to the grey colored PVC "sattellie dish pole" he erected against the fence.

Not a single question was ever asked about it.

73


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