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Author Topic: Will this Antenna Configuration work??  (Read 6023 times)
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KB2RSK
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« on: May 11, 2012, 07:07:22 AM »

 Iam limited to area of space
 100 - 120 feet north and sount
 onlly 20 - 30 feet east and west

 


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kb3rdt
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poop cup


« Reply #1 on: May 11, 2012, 08:10:15 AM »

What band you want to work and all depends on how high you put off the ground!
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K5UJ
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« Reply #2 on: May 11, 2012, 09:27:20 AM »

1.  It's spelled balun, short for balanced to unbalanced (balanced antenna to unbalanced feedline)

2.  Big problem with the wire bending back on itself to make a 20 or 30 degree angle.  Bends in antenna wires are okay provided they be >= 90 degrees.   Figure out a way to put a number of such bends on each side of the feedpoint to get the whole thing to fit on your property.

don't overlook that bends can also dip down and back up in the vertical plane (but it's better if they stay horizontal)
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W4NEQ
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« Reply #3 on: May 11, 2012, 09:41:30 AM »

In your limited space, I would consider a 102 foot center-fed dipole with either open-wire or ladder-line.  The precise length is not critical, but it is normally fed with a tuner.  This is a proven antenna.

If you can fold the ends back a bit (as previously advised, not to exceed 90 degrees.) You could go longer, but that would help only if you're wanting 160.  I prefer center-feed for horizontal antennas. 

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Ed/KB1HYS
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« Reply #4 on: May 11, 2012, 09:53:24 AM »

I will try and model it this evening, after I get home from work.
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
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« Reply #5 on: May 11, 2012, 10:38:36 AM »

As a sidebar, when I was a 13 year-old novice with very limited resources, I had this great idea to put up an 80 meter dipole in Vee configuration in the backyard.  Very easy and convenient to feed.  The angle was about 35 degrees, and it matched fine with a good SWR.

I made exactly zero contacts on that antenna, and later learned about cancellation of equal and opposing currents.

In the present case, much would depend upon frequency of operation, how much current flows in the folded section, and balun / coax losses since it will likely be quite reactive and require a tuner.
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KX5JT
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John-O-Phonic


« Reply #6 on: May 11, 2012, 12:02:00 PM »

Check out "linear loading"... I don't know much about it but it seems applicable here.  Maybe it can be used to some advantage here.  (Not Linear Amplifier but "linear loading" for wire antennas)
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AMI#1684
KB2RSK
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« Reply #7 on: May 11, 2012, 12:25:40 PM »

 Like maybe in a W  type pattern ?
  I am wondering what the distance between each W pattern I can go with out interfering with performance.
    Who knows it might be the cure  THE BIG W dipole   HI HI
 
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KB2WIG
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« Reply #8 on: May 11, 2012, 11:39:28 PM »

Look for some trees to support it.


klc


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WU2D
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CW is just a narrower version of AM


« Reply #9 on: May 12, 2012, 11:10:24 AM »

Even before I had my ticket I wanted to get an efficient antenna up for 80 meters so I consulted the brand new 1973 Handbook that my neighbors dad gave me. There was the perfect antenna for my second story bedroom shack.The antenna called for a half wave of wire to be wound on a 12 ft bamboo pole. So I went down to the hardware store and bought both, and came home with 125 feet of # 14 solid. I wound this on the pole with a 12 inch galvanized rod hose clamped at the top and shellacked the thing. Using a crude chimney clamp arrangement I somehow wrestled this monstrosity to the peak of the roof and installed it over my bedroom. The pole was fed with a roller inductor according to the article. Fortunately my Fair Radio ARC-5 had one of those so I was all set. The problem was the 25 feet between the ARC-5 and the antenna. I solved this by using some old 75 ohm coax which I connected between the chassis and antenna post and then I connected the hot of the far end to the bottom feed of the pole. Not knowing about ground, I left the shield open on that side. My ticket was on the way at last and I felt confident enough to tune it up using my best friend Billy's call. But how to tune it? I ended up inserting about a foot of hookup wire between the antenna jack and the center of the coax with a similar amount in parallel with a flashlight bulb in the center as a primitive tuning aid. It worked and at one point in the roller inductor's travel; the bulb lit up! Calling CQ boldly at 4PM after school on 3.7 MHz, a Canadian station immediately came back. I had made my first bootleg contact. Boy did I catch Hell from Billy's father, a severe German man, when he found out that I used his call when a QSL card arrived at Billy's house with my name on it. So if you want to achieve peak antenna efficiency, always consult the Handbook.
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Ed/KB1HYS
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« Reply #10 on: May 12, 2012, 04:50:18 PM »

Looking at the sketch, need to know the height, and a more accurate length of the lines.  Guessing from the description and drawing it's going to be a bit over 200ft from end to bitter end?

I'll send PM.

Did you want to try and cover 160 meters?  Single or multiple bands?

Anyway, unless it's pretty high up, it's going to be a cloud burner on 160 and 80. Good for local work (maybe 300 miles more or less YMMV).  above 40 it's going to develop lobes. I wouldn't try it above 20.

I live on a small (100x100) city lot and have used low zig-zag antennas quite a bit.  Best one, for me,  was the full wave 80 meter loop.

Also, Frank AHE has a good short dipole design here: http://amfone.net/Amforum/index.php?topic=24242.0

about halfway down the page.

If your yard has a clear stretch 120 ft long, you can get an 80 meter tuned dipole up.  Feed it with ladder line and you can mult-band it.  Tie both lines together, feed against ground as a top-loaded vertical.

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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
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