[TowerTalk] Placement of HF, UHF, and VHF antennas on one mast

[Roger (K8RI) on TT]

On 9/18/2014 2:03 PM, Joe Subich, W4TV wrote:

No real information, but experience:
http://www.rogerhalstead.com/ham_files/Tower29.htm

They worked well, but I had no way to measure real performance, or 
degradation.

The Bottom antenna: A TH-5 tribander is roughly at 100 feet.  The 7L 
6-meter is about 112-115 feet and the cross boom is close to 130 feet 
with 2 11L 144 antennas 14' apart and a pair of 12L 440s around 8' 
apart.  My Tower Project has the numbers on it.

Although they appeared to work well, that much mast is way too long.  It 
held up, but beat the snot out of the top antennas and destroyed a TB-3 
and a TB-4.  Either less mast or one that was much more rigid would 
likely have worked.  Better thrust bearing were called for with that 
much leverage.

73

Roger (K8RI)


> A good rule of thumb is to look up the stacking distance for the
> individual antenna (you do not provide enough information to know
> what they are) and place each antenna at least 1/2 the stacking
> distance (which is approximately 2 x the capture area) away from
> any lower frequency antenna.
>
> A good place to start is at 1/2 wave for antennas with booms less than
> one wavelength (e.g. 5 elements on 6 meters) and use 1/2 the boom
> length for antennas more than 1 wavelength long (e.g. more than 6 
> elements for the typical 2 meter designs).  There are more rigorous
> calculations in the various UHF/VHF antenna books but "half the boom
> length with a 1/2 wave minimum" will get you "in the ballpark".
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 2014-09-18 1:11 PM, Marv Shelton wrote:
>> I'm about to complete my annual tower work and have added a few new 
>> antennas to the mast.  I have done some reasearch but found 
>> conflicting information on how far apart to seperate antennas on one 
>> mast. The info that makes the most sense talks about the capture area 
>> of the antenna.  I am looking at a "stack" consisting of a tribander, 
>> a 6m beam, and beams for 144, 220, 440 and 1296 MHz.
>> Does anyone here have experience or a link to so e good reference 
>> material about how far apart to place these antennas? I have about 15 
>> - 17 feet of mast to work with.
>>
>> Marv - WA2BFW
>> _______________________________________________
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>>
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-- 

73

Roger (K8RI)


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