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 Looking for opinion(s) regarding vertical in limited space
Keigan  [Member]
3/7/2012 11:31:26 PM
I have a Shakespeare military antenna that is 32' tall, below that I have an SGC-230 coupler, below that I am establishing 32' of aluminum mast, + hooked to antenna and - side hooked to mast. In the pure form this is a 64' vertical dipole that will rest on the ground. I'll add in guy wires to the mast that are wire to represent counterpoise of varied length. Pushing this with a maximum of 200w from an Icom 7700.

What say the hive?

Thanks, KU0Y
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stanprophet09  [Team Member]
3/7/2012 11:36:33 PM
The problem is with a vertical Dipole you need to run the coax out away from the antenna at 90 degrees from the center at least 1/4 wavelength. The other option is to run the coax up the center of the mast. If you do not you will be generating a large amount of RF on the coax braid, and you will have common mode currents like a mother.

I use a vertical dipole here at the house, even with the SGC at the center and the coax at 90 degrees, I get common modes due to close proximity, and the desk with the radio being higher than the center of the dipole. (3rd Floor Shack)

ETA: Details
Keigan  [Member]
3/8/2012 12:29:22 AM
Yes, the coax will run down the center of the mast which will assist.
aa777888-2  [Member]
3/8/2012 6:01:56 AM
Jealous of 7700

Sounds like a very well thought out antenna system.


Keigan  [Member]
3/8/2012 6:57:21 AM
My shack is 12 feet above ground. I'm not certain how far away the antenna will be, need to prunes tree before I can determine the the position of the base. The mast is made up of four sections of aluminum tubing each eight feet long - Penninger Radoi has nice stuff. The SGC will be mounted at the top of the mast, with the antenna mounted to the very end of the mast, coax can run down the mast and exit near the bottom through a hole I have drilled in the side of the tube. The backyard can support the base of the mast being 60 feet from the base of the shack, poor trees.

Using a single piece of coax 100' long, the SGC has 12 feet down the mast which will require 20' of coax to reach dirt, then I have about 20' from dirt to shack entrance point, leaving me with 60' to support the distance from shack base to mast base.

My thoughts are to use wire rope as guy wires, providing counterpose lengths that connect just below the SGC and run to the ground. Need to find my geometry book to calc the long side of the right triangle, where leg A is 32' and leg B is 32'. At least 4 wire ropes, one on each 90 degree around the base.
aa777888-2  [Member]
3/8/2012 7:51:27 AM
Originally Posted By Keigan:
My thoughts are to use wire rope as guy wires, providing counterpose lengths that connect just below the SGC and run to the ground. Need to find my geometry book to calc the long side of the right triangle, where leg A is 32' and leg B is 32'. At least 4 wire ropes, one on each 90 degree around the base.


In this case you should use non-conductive guy ropes. Kevlar or equivalent (Vectran, etc.).
wdlsguy  [Member]
3/8/2012 8:48:43 AM
My thoughts are to use wire rope as guy wires, providing counterpose lengths that connect just below the SGC and run to the ground. Need to find my geometry book to calc the long side of the right triangle, where leg A is 32' and leg B is 32'. At least 4 wire ropes, one on each 90 degree around the base.

I agree with aa777888-2. A vertical dipole doesn't need (or want) a counterpoise (your mast is the other half of the antenna).

A vertical monopole needs a counterpoise or radial system though (the counterpoise / radial system is the other half of the antenna).

I assume the Shakespeare antenna and the mast will be insulated from each other? I also assume the base of the mast will be insulated from the earth?

Is this setup DC grounded for static discharge? What about lightning protection?
Keigan  [Member]
3/8/2012 10:00:37 AM
Need some modeling software to review performance of the antenna.

I can setup in one of the following configurations:

A) 32' vertical on top of the SGC +, insulated from the 32' mast, with counterpose wires around to the SGC -

B) 32' vertical on top of the SGC +, connecting the 32' mast to the SGC - , insulating the base of the mast, no counterpose

C) 32' vertical on top of the SGC +, connecting the 32' mast to the SGC - and adding counterpose also connected to the SGC -

Keigan  [Member]
4/10/2012 11:53:29 AM
Well, I broke the antenna and it is now 24' tall until a replacement segment is delivered by Shakespeare.

It works!

My previous deployment of this antenna was a a vertical but I only had one counterpose element, was not functional on 80m or 160m.

My first deployment of the vertical dipole was interesting but not fully tested. I hooked the SGC-230 + side to the 24' antenna, then the - to the 24' mast and placed everything in a 5 gallon bucket to insulate from ground. This worked on all bands up to 80m and I could tune to 160m but did not have the opportunity to transmit. The significant difference is that the vertical dipole is closer to being balanced, so the SGC is doing its thing in a more efficient manner. But, I did have common mode coming back to the transmitter.

My second deployment of the vertical dipole is interesting and is fully functional on all HF bands including 160m - last night was the first time i've held a GSO on 160m. I have a 30' flatbed gooseneck trailer that I use for storage, I decided to bolt my mast to the trailer so that the trailer contributes as counterpoise and reflector. So same config as before, now with the mast connected to the frame of the trailer, trailer jack stands touching ground. Last night I could hear MI at S9 but the guy was too long winded, connected to entire West Coast on 40m, 80m and 160m - all with S8 and 10 over reports. I'll try more on Wednesday night.

Cheers, Keigan
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