[TowerTalk] Mounting 10m/15m/20m monobanders -- single mast.

[KT2Q]

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