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Author Topic: Homebrew Dual Beam Pro  (Read 1804 times)
G0VKT
Member

Posts: 64




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« on: April 26, 2013, 04:42:08 AM »

I am thinking of making one of these:

http://www.proantennas.co.uk/dualbeampro.htm

It is a non resonant dipole design with capacity end loading. Has anyone modeled this antenna?
What I am interested to know is the SWR on each band to get an idea of the coax losses.

It would fit very nicely in the space that I have. The plan would be to have a separate antenna for 80 and 40.

Paul.

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AA4PB
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Posts: 12899




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« Reply #1 on: April 26, 2013, 05:28:27 AM »

Looking at the specs, my first question would be how can an antenna that is half the physical size of a dipole have 4.6dB gain over a dipole on 20M? There must be some "specsmanship" going on somewhere.

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W4OP
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Posts: 436


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« Reply #2 on: April 26, 2013, 05:50:36 AM »

They are quoting the gain with ground reflection gain included.

Dale W4OP
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G3TXQ
Member

Posts: 1524




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« Reply #3 on: April 26, 2013, 12:51:48 PM »

Paul,

Modelled at 33ft above average ground, and assuming a perfect 9:1 balun (??), I see SWR(50)s of:

20m 19.2:1
17m 9.2:1
15m 5.9:1
12m 4.5:1
10m 4.6:1

You could of course omit the balun and feed with ladderline.

Hope that helps,
Steve G3TXQ
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G0VKT
Member

Posts: 64




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« Reply #4 on: April 29, 2013, 01:29:57 AM »

Thanks Steve. Yes that helps a lot. The pole I have would put the antenna about 10m above ground and the feeder length will be about 12m.
Ladderline could well be a possibility. I will need to look into that.

Paul.
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IZ0IRH
Member

Posts: 1




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« Reply #5 on: June 06, 2013, 04:25:13 AM »

Hello, my name is Mario, my callsign is IZ0IRH, i was looking for some info about this antenna. I have tried to model it by using MMANA-GAL and I assumed both 9:1 as a 4:1 balun, but I got very different values fo SWR. Almost surely I made a mistake in including the balun in the model, as I just put it as looking into Z0 = 200, and Z0 = 450 (referred to 50 Ohm) in the setup definition.
 How did you model the antenna and the balun? Have you included also the reactive component (some R + JX) in the balun? Thanks a lot for any answer to help.
73
IZ0IRH Mario

Paul,

Modelled at 33ft above average ground, and assuming a perfect 9:1 balun (??), I see SWR(50)s of:

20m 19.2:1
17m 9.2:1
15m 5.9:1
12m 4.5:1
10m 4.6:1

You could of course omit the balun and feed with ladderline.

Hope that helps,
Steve G3TXQ
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G3TXQ
Member

Posts: 1524




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« Reply #6 on: June 06, 2013, 04:53:18 AM »

Hi Mario,

I did exactly as you did - I used the alternative reference impedance of 450 Ohms.

73,
Steve G3TXQ
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