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Antenna spacing?



 
 
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  #1  
Old February 20th 05, 02:38 AM
Harry
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Default Antenna spacing?

I have three yagi's that I want to mount on one tower.
1)Hy-Gain TH3-MK3 three element HF tribander
2)Cushcraft 32-19 nineteen element Two meter yagi
3)Cushcraft A50-3S three element six meter beam
I installed a 40' Glen Martin with hazier last fall and I want to place
these three antennas on a mast at the top of this tower. My question is,
How far above the tower should the first antenna be, is there any
particular order to mounting, how far apart should these antennas be
from each other? I'm using Kevlar guys, so they shouldn't cause any
problems. The tower is grounded at all three legs.
TIA
Harry

  #2  
Old February 20th 05, 02:41 PM
Dennis Kaylor
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hey harry
i recently put up 3 long boomed yagis
a M2 6M7 which is 7eles on a 27ft boom 6 meters
KLM 16LBX 16ele on a 28ft boom 2 meters
KLM 30LBX 30ele 70cm on a 22ft boom
and what i did is mounted the 6 meters at the top of the tower 40ft and
stacked the others 5ft apart
and they work fine i do get into the front end of the differnt radios
when i transmit so i think i got them a bit close together but it hasnt
hurt the performance or the SWR of any of the antennas
in your case i think i would put the HF tribander at the bottom of the
stack then 5ft above that i would mount the long boomed 2 meter yagi
then 5ft from it the 6 meter antenna
usually i would stack them the higher in freq the higher on the mast but
since the 2 meter yagi has a lot longer boom i would put it in the
middle to you have room for the boom supports
good luck
Harry wrote:
I have three yagi's that I want to mount on one tower.
1)Hy-Gain TH3-MK3 three element HF tribander
2)Cushcraft 32-19 nineteen element Two meter yagi
3)Cushcraft A50-3S three element six meter beam
I installed a 40' Glen Martin with hazier last fall and I want to place
these three antennas on a mast at the top of this tower. My question is,
How far above the tower should the first antenna be, is there any
particular order to mounting, how far apart should these antennas be
from each other? I'm using Kevlar guys, so they shouldn't cause any
problems. The tower is grounded at all three legs.
TIA
Harry

  #3  
Old February 20th 05, 05:03 PM
Crazy George
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Default

Harry:

Here is the general rule of thumb way to approach this requirement. With the booms aligned, each antenna only "sees" a
lower frequency (larger) antenna. So start at the top with the 2 meter antenna. It needs to be a half wavelength at 2
(~40 inches) from the next thing. And so on to the others. The 6 meter should be about 100 inches from the tribander,
and the tribander doesn't care. It looks mechanically clumsy, but putting the 2 meter half way between the tribander on
the bottom and the six meter on top with the 6 and triband 100 inches apart is close to the best compact arrangement.

--
Crazy George
the ATTGlobal.net address is a SPAM trap. Use the att dot biz extension to reach me.


  #4  
Old February 20th 05, 06:52 PM
Allodoxaphobia
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On Sun, 20 Feb 2005 10:03:23 -0600, Crazy George wrote:

It looks mechanically clumsy,


I don't think so! HI!HI!

but putting the 2 meter half way between the tribander on
the bottom and the six meter on top with the 6 and triband 100
inches apart is close to the best compact arrangement.


Because that's the assembly I have here.

A low res JPEG showing my 40' Rohn just that-a-way:

http://jonz.net/Home.html


Seems to work quite nicely --- compared to leaving it stacked in the
corner of the garage while anguishing over finding The Perfect Solution.

73
Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK
  #5  
Old February 20th 05, 08:30 PM
[email protected]
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On Sat, 19 Feb 2005 20:38:29 -0500, Harry wrote:

I have three yagi's that I want to mount on one tower.
1)Hy-Gain TH3-MK3 three element HF tribander
2)Cushcraft 32-19 nineteen element Two meter yagi
3)Cushcraft A50-3S three element six meter beam
I installed a 40' Glen Martin with hazier last fall and I want to place
these three antennas on a mast at the top of this tower. My question is,
..............................snipped.......... ..........


I have 28Ft (from ground level) Rohn 25. My set up for all modes on
6/2/70cm is as follows.

Top going down:

Top Arrow OSJ146/440 Jpole
Just below is a 215WB (15element CC)
41" below that is a 5Element UHF (horizontal Arrow 440-5s)
42" below the UHF is the Arrow 52-4s (6m 4 element beam)
(total distance between the 2m and 6m beams is 81".)

The combined tower and mast height puts the 6m beam more than
14ft higher than the roof of the house and exactly 30ft above ground.
My tower is bracketed to the side of a low ranch house.

At the 25ft level of the tower is a lanyard for raising and lowering
the tower end of wire antennas. Those wires extend to trees and poles
elsewhere on the property. I set up two of these on two of the legs
of the tower. One carries my 24ft EDZ for 6m aimed SW
and the other has a general use wire running NNW for HF listening.

I also have vertical dipole for 6m on the south leg at about 20ft
(center of the antenna) of of the tower for local 6m FM use and on the
north leg a CuCactus for 2m/70cm (15ft to the base of it) for local
use.

This arrangement is optimal for the 2m and 6m and appears effective
for the UHF as well. The goal was to keep the mast extending above
the tapered section (25AG) to under 8ft as I only had an 11ft mast.

Seems to be effective for F2 and Es and to the limits of 4elements
on 6m for tropo. The other effect is the J at the top is both
effective due to height and also not having radials doesn't interfere
with the 215WB just below it. The UHF was installed for later use
as I only have limited UHF capability and I expect to replace it with
something in the 11-15 element range when capability expands.

Allison
KB1GMX FN42
  #6  
Old February 21st 05, 12:35 AM
Allodoxaphobia
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Posts: n/a
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On 20 Feb 2005 17:52:57 GMT, Allodoxaphobia wrote:
On Sun, 20 Feb 2005 10:03:23 -0600, Crazy George wrote:

It looks mechanically clumsy,


I don't think so! HI!HI!

but putting the 2 meter half way between the tribander on
the bottom and the six meter on top with the 6 and triband 100
inches apart is close to the best compact arrangement.


Because that's the assembly I have here.

A low res JPEG showing my 40' Rohn just that-a-way:

http://jonz.net/Home.html


I knew I had a better JPEG of it around here somewhe

http://jonz.net/W3DHJ/images/W3DHJ_Tower.jpeg

From the top - down: CC A50-3S , an old CC 215WB , and the CC A3S.
That's a home-brew 2M vertical on the forward boom of the A3S.

Sigh... It all comes down in a couple of months.
Moving to a new Grid Square....

73
Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK
 




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