I have always been curious why someone would invert the stack. It seems
that the mechanical disadvantage of the larger antenna on top of the
mast would be more of a problem than any advantage. There is really no
height advantage as you are usually only talking about a few feet one
way or the other out of say 100 feet or so tower height.
Is there any advantage as far as higher vertical radiation angles go
either way?
Why invert?
73
Gary K4FMX
Don Havlicek wrote:
> My preference, as always, is to INVERT the Xmas-tree, with the 20m on
> top, 15m below it, and 10m below that. Used that arrangement for many
> years in the 1980's and early 90's.
> Don
> N8DE
>
> KT2Q wrote:
>
>>All:
>>
>>Thanks for the replies regarding the mounting of 15 and 20 meter monobanders
>>on a single mast. Although there might be exceptions, the general agreement
>>seems to be that there is a slight detuning effect in F/B with mounting
>>distances no less than 8 to 10 feet between the 20m/15m antennas.
>>
>>John, KK9A / P40A explained that his 15 meter monobander shows a slight F/B
>>loss with the antenna 8 feet above the 20m monobander. His 20 meter
>>monobander seems unaffected from the 8 foot spacing.
>>
>>It would be interesting to model the effect to find the best spacing (within
>>reason) for mounting monobanders on the same mast. I have a 20 foot mast and
>>can mount 20m and 15m monobanders 10 feet apart and have enough room to
>>mount my existing 10/12 meter Force12 Yagi about 10 feet above the 15m
>>monobander. But the question is what effect the third antenna might have on
>>the others? Which is the least effected etc.
>>
>>The 4 and 5 element M2 / Force12 monobanders for 20 meter and 15 meters seem
>>like a good idea for improved performance over shorter-boom multi-band
>>interlaced designs that utilize 2/3 or so of actual boom length. But there
>>is the expense and tower loading to consider.
>>
>>Obviously, the improved F/B and forward gain would depend on how long a boom
>>length you're willing to go with or can afford. When you look at the
>>numbers, it's obvious that it takes quite a bit of additional boom length to
>>add an extra 3db.
>>
>>Any additional suggestions on mast mounting distance for monobanders would
>>be greatly appreciated. Comparisons between different monobanders would be
>>appreciated as well.
>>
>>73 Tony KT2Q
>>
>>
>>
>>_______________________________________________
>>
>>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>>questions and ask for Sherman, W2FLA.
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk@contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
> questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
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