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Author Topic: 40-10 Doublet Antenna  (Read 5587 times)
KB8UUM
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Posts: 11




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« on: March 28, 2007, 05:28:25 AM »

Anyone have any suggestions about making a 44' doublet? Curious to know what the best feed would be to use? I am limited in space and it seems like it will just about fit. Also curious to know how much luck you guys have had with it on the air. Thanks for all the help.

Geoff
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AA4PB
Member

Posts: 14422




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« Reply #1 on: March 28, 2007, 12:49:20 PM »

If you are going to operate the doublet on all bands with a tuner then you must feed it with a low loss cable like open-wire or ladder line if you expect much in the way of performance. Coax will have too much loss on some bands due to the mismatch and high SWR on the feed line. Remember, the tuner will not lower the SWR on the feed line.
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Bob  AA4PB
Garrisonville, VA
W5ESE
Member

Posts: 550


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« Reply #2 on: March 28, 2007, 02:21:03 PM »

Geoff,

Realistically, you have 3 choices for feeding your
44' doublet. This is in decreasing order of
preference.

1) open wire ladder line
2) window line
3) tv twinlead

1) will have the lowest loss, and is the least
affected by ice/water.

2) is intermediate. it's quite popular and available
at many ham stores.

3) is available at most any radio shack store.

I use 1) at home and 3) when operating portable.

73
Scott
W5ESE
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AE6RF
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Posts: 151


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« Reply #3 on: March 30, 2007, 01:43:30 PM »

Google "Norcal doublet" for a 44' doublet made out of computer ribbon cable.

Easy to make. Enough people have used them so that if their performance was horrid somebody would have noticed...

73 de Donald
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NG0K
Member

Posts: 342




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« Reply #4 on: March 31, 2007, 06:34:23 AM »

I would suggest a 52 foot doublet minimum?  Use twinlead or 450 ladder.  I realize the 44 feet is popular due to it's size.  It's a double extended zepp on 10 meters.  But on 40m it's very short and the feedline losses will be significant, even with 450 ladder.  I had one for a while and it worked great on the high bands but it was terrible on 40 meters.  

W8JI has a nice write up on this here:  http://www.w8ji.com/short_dipoles_and_problems.htm

Good Luck on whatever you decide,
73, Doug
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73, Doug - NG0K
NG0K
Member

Posts: 342




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« Reply #5 on: March 31, 2007, 06:37:14 AM »

Also, don't be afraid to bend the ends down or sideways a little to fit your space.  As long as you have at least 50 to 60% horizontal, it won't make a very noticable difference.

Doug
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73, Doug - NG0K
WW5AA
Member

Posts: 2086




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« Reply #6 on: April 02, 2007, 11:08:59 AM »

Good place to start:

http://www.cebik.com/gup/gup34.html

73, de Lindy
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KB8UUM
Member

Posts: 11




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« Reply #7 on: May 08, 2007, 06:03:43 PM »

Has anyone tried an 18ft center fed doublet vertical for 20-10M??
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KE6VG
Member

Posts: 310




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« Reply #8 on: August 07, 2007, 07:12:54 AM »

I tried a 32' vertical doublet fed with 300 ohm twinlead. I used one of those large windsock poles. It acturally worked quite well. I had mine too close to the stucco house though. It had a roaring signal into Texas, but my coax fed 20 meter dipole at 30' seemed to win on most other paths.
My favorite for DX now is my half-square. I have one set up for 40 meters using two of the 32' winsock poles. I use one of the PAR Electronics transformers from their 1/2 wave antnenna. becuase it is compact.
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