-=> On 11-23-97  08:21, Ed Kriston said to All,<=-
-=>"About In Attic Dipole...,"<=-
 
Hi, Ed;
 
 EK> To anyone who can help.  I live in a condo townhouse and have the
 EK> normal restrictions on antennas.  At present I am running a G5RV
 EK> (105'), 10m dipole amd an AR-270 dual bander in the attic.  I have no
 EK> problem with any antennas except the G5RV.  Attic is 20 X 20, center of
 EK> dipole is on the East side and best described as a flat top with two J
 EK> ends.  From the center each side is about 10 feet long, 90 deg bend
 EK> then runs length of house, 90 deg bend runs approx 5 feet, 90 deg bend
 EK> and remainder runs about half way back toward center.  I want something
 EK> shorter that will fit in the attic without as many bends.
 
I'm sorry, but you aren't going to get an efficent antenna that's much
less than 1/2 wavelength long.  OTOH, your attic only has 80 Ft. of
"corner space," and the antenna is 105'?  Since you want to keep the ends
as far apart as possible, I see two options: 1 is the foldback you are
using, the other, which I would suggest trying, a zig-zag pattern like:
 ______________________________
|       |~~~|   |~~~|   |~~~~||  This is a variation of an idea I read
| ______|   |   |   |   |    ||  about some time ago - a Ham hid a dipole
| |     \   |___|   |___|    ||  under his wooden deck, and it worked
| |_____  \                  ||  well for him.  Only in this case you
|      |    \            ____||  would be using a G5RV instead of a
| _____|     To xcvr     |    |  plain dipole.  You will have to
| |                      |____|  experiment, (or do some math), to
| |____     20 X 20           |  determine just how big to make the
|      |    attic             |  zig-zags so that it comes out roughly as
| _____|    ___               |  I have drawn it here.  You might even
| |        |   |              |  mount it on the underside of the roof.
| |________|   |              |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
Instead of having the feedpoint at the center of the side, you might try
moving it to a corner, and just follow the sides of the attic.  That may
or may not help.  There is a possability that it is too close to other
antennas or other metal.  This would include such things as house wiring,
heating ducts/pipes, metal in the roofing, etc.  Keep the different
antennas as separated as possible, both from each other and from the
feedlines for the other antennas.
 
 EK> I know that I will probably not find anything that will fit without
 EK> some bends.  I have looked at just about every antenna design program
 EK> that I can find, none show how to do antennas with traps.  I figure
 EK> that my best approach to shorten the run is to use traps.  It won't be
 EK> outside in the weather, so it might not be a problem.
 
 EK> ... I hope to modify the G5RV with traps and do away with the
 EK> ladder line part of it.
 
You DON'T want to remove the ladder line!  That is part of the entire
system design, and removing or shortening it will only degrade the
system's performance.  If it wasn't needed, you can bet your last dollar
it wouldn't be there.  Just make sure you keep it at least a few inches
from any signifigant amounts of metal, and especially don't run it through
any pipe.  If you need to cut anything, cut the coax part.
 
 EK> BTW,  operating station is in the basement and there are two floors
 EK> of living area to the attic.  Hope to run shielded coax through the
 EK> living areas.
 
I understand your desire to use coax through the living areas, but if
it means cutting the ladder line, don't.  Also, keep the ladder line as
straight as possible.  (Don't roll/coil it up do get it "out of the way."
 
Also, be advised that on SOME bands, that ladder line MAY be a radiator,
so you need to be aware that you MAY be exposing your family to more EMI
than they are already getting from the attic antennas.  If you have any
kind of a field strength meter, (even a simple crystal set with a meter),
I suggest checking this out.  This is why I don't like attic antennas:
They expose the Ham and anyone else in the area to relatively high levels
of RF - something the FCC has recently instituted new rules about.
 
 EK> Thanks for any help.
 
My pleasure.  Please let me know how things work out.
 
N3WJA DE KB9QPM/AE  73 OM
   Ivy
 
 
 
... Antenna... Isn't that Uncle Harry's wife?
 
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           ³  SysOp: Ivy's WALL BBS - 6 Networks 920-457-9255  ³
           ³             IMHO: 5 WPM for EVERYONE.             ³
           ³           KB9QPM/AE as of 11/19/97 :->>           ³
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