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Author Topic: Dipole Questions  (Read 1149 times)
KB1FOT
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« on: June 05, 2013, 02:29:25 PM »

Hello All,

Years ago (well around 2000) I got my ham license, shortly thereafter my children were born and Ham radio kinda was on the backburner.

Now I am trying to get everything back up and running, my daughter had to move rooms, into my old shack, and I had to fit everything into a tiny room, anyway, good in a way, was an opportunity to sort things out, and get everything re-set up.

Now I am a bit out of things.... I apologize.....

I only had a 20M dipole on my roof, in an inverted V-Sloper combination. It worked well and made a lot of QSO's, especially on PSK31 which I worked a lot... At some point a plumber was working on my roof, and he came down with my Dipole cut to pieces, he thought it was old, and since he was working on the roof, he took it off... So right now I am contemplating a new antenna setup.

I have a flat roof with a chimney, the chimey I would like to use as a support for a few dipoles.

I was thinking to install three dipoles for 10,17 and 20 meters, and a longwire/endfed for 40 meters.

I am only able to use one site of the chimney for support as it off to the side of the house, and thus would like to install all three dipoles in the inverted V/Sloper combination in close proximity to eachother. So at the lowest point on the chimney the feedpoint would be for the 10M, a little up the 17M and the top one the 20M, the endfed antenna I have to slope/bend around the roof a bit, to fit it in the limited space on the roof.



Question is: Would that give any problems, the radiators are fairly close to eachother.

The 10,17 and 40 will be connected to a switch and then to antenna connector 2 on my rig, and the 20M dipole permanently on  the Antenna 1 connector.

Anyway,I as just wondering if the dipoles would be ok in this configuration...


Thanks for your Help!

Rian - KB1FOT

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W4OP
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« Reply #1 on: June 05, 2013, 02:58:21 PM »

Hi Rian,
Google fan dipole. For those three bands- 20/17/10, you can use one center insulator and one feedline. Space the individual wires from one another with insulated spreaders.
Here is just one link of many:
http://www.hamuniverse.com/multidipole.html

Dale W4OP
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GW3OQK
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« Reply #2 on: June 06, 2013, 01:42:21 AM »

Rian,
what about having just one dipole, or doublet, with the maximum length you can achieve each side. Feed with ladder line to keep it balanced and prevent radiation from the feeder. Connect to a balanced tuner like a Z-Match and it would tune up and radiate on all bands 40 to 10. (Would do on 60 & 80 as well I expect.) The balanced tuner would take care of the undefinable radiation resistances and reactances and convert it to 50 ohms. Just my simple thought.
Andrew 
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WX7G
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« Reply #3 on: June 06, 2013, 02:30:24 AM »

Rian, while what you propose will certainly work you can achieve similar performance for less trouble by following Andrew's advice. A dipole 50 to 67' long and bent to fit on the roof and fed in the center with Ladder Line or TV Twin lead will get you on 40-10 meters. Many of the MFJ antenna tuners will tune it and I recommend the MFJ-901B at $100.
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