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Author Topic: "disguised" dipole  (Read 47822 times)
K4EZD
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Posts: 88




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« on: August 28, 2013, 09:59:20 AM »

I can get away with a 20M dipole at my HOA neighborhood in my backyard if the coax is almost against the house and leading straight down.  Would a dipole work if the center balun and coax were against the house (vinyl siding) and the legs of the dipole were each extended out at about a 30 degree angle from the center to poles on each side of my yard disguised with purple martin houses on the tops.  The pattern from a sky view would be a wide V shape.  How would that affect the signal pattern?  When I tried a typical dipole the center hanging coax attracted too much attention. 

Thanks.
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W1JKA
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Posts: 1619




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« Reply #1 on: August 28, 2013, 10:37:09 AM »

  Hams by necessity have been putting up and using dipoles with success in various configurations since the get go, i.e. zig zag legs, end hanging down, sloping, vertical, leg or legs angled such as your idea. Just  put up your horiz. vee and compare with your present one. Yes, signal patterns will vary a bit depending on your qth ground conditions in relationship to each different configuration but only you can decide if this is for the better or not. Experiment and Good luck.
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WB6BYU
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Posts: 13019




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« Reply #2 on: August 28, 2013, 11:13:55 AM »

Even putting a right angle bend in the middle of a dipole doesn't affect the pattern
a lot.  What will make more of a difference will be the metal roofing trim, rain gutters,
wiring, etc. in the house.

But you do what you gotta do to get on the air.  Angling the wires away from the
house may be somewhat better than just laying them on the roof or running them
in a plastic rain gutter.  Don't be surprised if the resonant frequency shifts somewhat
(a bent dipole requires slightly longer wires for resonance than a straight one, and
the effect of the house is unpredictable without knowing more about it.)


If the coax and balun are too noticeable, use a parallel-conductor feedline made from
thin wire, at least far enough to get out of sight.  Might have to do a bit of impedance
matching, but that's not difficult.  In one house I had the feedpoint inside the house
with the antenna wires running out the windows on two sides, and you can do similar
things with attic vents.


Put it up however you can and get on the air.  Over time you will think of ways to
improve it if you find it doesn't work very well.
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N4JTE
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Posts: 1152




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« Reply #3 on: August 30, 2013, 05:25:40 PM »


Sounds like an elegant solution, like the birdhouse thing, hi
Yes it will work and not sure if you mentioned the height but seems like your good to go and will have decent receive and signal, not to worry too much about the vinyl siding if using coax feedline, have fun.
Bob
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KQ6Q
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Posts: 965




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« Reply #4 on: September 22, 2013, 09:33:16 PM »

Your idea will work, and you'll have some directivity away from the house, which is good. Don't expect to work much through the house.
I did a similar setup back in the Air Force - a three story concrete BOQ building, my room on the ground floor near the center. outside access balconies on floors 2 and three.
I hung a dipole center connector (no balun) near the edge of the roof, and ran two 45 foot wires out to stairwells that projected from the same side of the building. The wire ends near the stairwells were lower than the center feed point. The antenna was a 3/2 wave dipole on 20m. Building faced north, so my best lobes were NW and NE, which happened to point to Europe, and Japan and NA, since I was in southern Thailand.
I never had to call CQ more than once to make contacts !
Fred, KQ6Q (HS2AJG at the time I used this antenna!)
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WX7G
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Posts: 5918




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« Reply #5 on: September 22, 2013, 10:20:53 PM »

Wood frame houses are transparent to HF and your antenna will work just fine in all directions. 
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N3AEG
Member

Posts: 37




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« Reply #6 on: September 24, 2013, 06:52:01 AM »

I live in a condo and can't run the cable off of the balcony and it can't be visible.  I was thinking about using a middle fed 20m dipole but putting the feedline connector in the center of the desk and run each side of the dipole along the decking and then up the side of the balcony.  This would sort of form a "U" shape.  I'll either use a dipole or an end fed "matchbook" style antenna in the same configuration.  The biggest problem is the dipole is black wire which is pretty obvious (unless I build one).  If I use the end fed version, I can use 25' of white wire which will blend in.

Will a "U" shape antenna work to some extent?
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WB6BYU
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Posts: 13019




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« Reply #7 on: September 24, 2013, 09:07:38 AM »

Quote from: KC3AZL

Will a "U" shape antenna work to some extent?



Yes, it will.  The longer the center section the better it works, of course, but even if you
can get half the length horizontal it should work OK.  (Making the base of the U only 2 feet
long isn't going to work well on 20m, however.)

Note that a bent dipole will require a little more wire than a straight one if you are trying
to adjust it to resonance, but if you are using a tuner then it should be close enough.

White insulated wire works fine, either #12 house wire or #22 stranded hookup wire (which
is easier to work with, and easier to hide in the cracks) or whatever you can find.  Small magnet
wire can also be inconspicuous.
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N3AEG
Member

Posts: 37




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« Reply #8 on: September 24, 2013, 09:36:47 AM »

Thanks.  I haven't decided on the HF rig as of yet, but it will have a internal or external tuner.
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WA7SGS
Member

Posts: 38




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« Reply #9 on: September 25, 2013, 05:47:14 PM »

Having a J-pole mount like those used for satellite dishes that previously had my Sirio D-27 dipole on it, I had the balun attached and it does not really stand out.  One could even paint the balun another color if one wanted.  The coax is wrapped along the pole mount with plastic ties to secure it.  The 20m dipole wire is blue and hard to see unless one knows where to look and at the proper angle.  With a peaked roof and using the backside of the place, no one can even tell from the street or neighboring houses that there is even anything there.  A short J-pole is not a visual Big Deal as it is a vertical pipe that from any sort of distance will resemble the other small vertical venting pipes commonly found on roofs.

Hiding in plain sight is fun!  As for how good the dipole does, it handles 20m, 15m, part of 40m and all five channels of 60m with the AT-100ProII antenna tuner.  It's not as good as a big beam with rotor setup but no one complains about a Big Ugly Antenna (non-ham view of those things...LOL!) and I get to QSO so I call it good, declare victory and sleep with a clear conscience.

Rick   
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KB2WIG
Member

Posts: 114




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« Reply #10 on: September 25, 2013, 08:18:50 PM »

"  Hiding in plain sight is fun! "

I once lived on the 3rd floor of a 3 floor building. Watt I did was run 'cable tv' coax on the side of the building. A coax splitter (with the guts pulled out) was in the middle. Add a tuner and Shazam!   And no one had to know that it was my dipole.


klc
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WA9UAA
Member

Posts: 309




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« Reply #11 on: September 26, 2013, 08:45:30 AM »

Once while in college and in an apartment for the summer, I loaded up the shield of my Cable TV feed and worked it against a ground wire connected to a pipe in the loo.
73,
Rob
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KX8N
Member

Posts: 543




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« Reply #12 on: October 05, 2013, 06:23:27 PM »

Give it a try and see what happens! I've been in apartments for years and the big thing I've always found is that anything outside beats anything inside (even though something inside is better than nothing).
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AB9TA
Member

Posts: 19




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« Reply #13 on: October 09, 2013, 05:05:12 PM »

If you can, check to make sure the insulation in the walls or in the attic is not the type that is faced with aluminium foil. Also check to see that the vapor barrier isn't aluminium. That can really detune your antenna and/or capacitivly couple all your signal to ground. (Had it happen to me once in a rented house, I simply could not radiate any signal at all on 80M - The dipole was up against the house hidden in the wood siding, of course right next to the giant sheets of aluminium foil.)

Otherwise, as mentioned before, your wooden structure is invisible to HF. And, it is fun to operate stealth.. It's a challenge. Not only do you learn antenna theory, you will learn about camoflage and hiding in plain site.
For example, I once told my landlord that I was a bird lover and got permission in install a birdhouse on a 10' copper pipe in the back yard. Amazingly, if you lay small gauge black stranded wire in the grass, it disappears.. Best of all, the whole thing tuned up and worked decently from 20M - 6M.. An RF miracle!!!!

In my experiences with stealth operating, they key has been to get as much wire up as practical - get as close to the size of a full length dipole as possible. You can then bend it up as necessary to fit the allowed space. Bends should preferably be near the far ends of the wire.

Just get something up and experiment, you can get a decent signal out by making and hiding your own wire antenna creations.. A compromise antenna is far better that no antenna at all.
Just remember that creativity and an antenna matching unit (tuner) will be your best friends.

73!
Bill AB9TA
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M6GOM
Member

Posts: 875




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« Reply #14 on: October 12, 2013, 02:48:23 AM »

Even putting a right angle bend in the middle of a dipole doesn't affect the pattern
a lot. 

Actually it does and quite substantially.

If one leg is pointing north and the other east, the pattern is NE/SW.

Basically if you bend it from the centre, the directivity is at half the angle between the legs.

Knowing that you can use it to your advantage. A friend of mine wanted to be able to work the states but the space for a dipole was in such a way that it wasn't going to happen with a regular dipole shape. Basically his house was N/S so from the UK great for working the Carribean, not so good for North America, especially the more northern and western sides. So what I did was build one _| shaped which gave an azimuth pattern going NW/SE.
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