Topband: Beet Antenna Choice?

[Joe Subich, W4TV]

On 2018-09-27 5:01 PM, Edward via Topband wrote:
 >
 > I have three crank-up towers spaced 35' apart. T

With towers spaced 1/16 wavelength, they will almost certainly
all be coupled to each other.  The coupling will be greatest
when they are nearest to resonance.

Your "tower #3" is probably very close to resonant on 160 meters
depending on the top loading.  As a first approximation, take
1/2 the boom length of the longest boom yagi and add it to the
height of its attachment to the mast.  If, for example, you have
a 32' boom 6 meter yagi 15' up the mast -> 106 + 15 + 16 = 137'

I would strongly consider gamma (or omega) matching the 160' tower
and then using skirts to detune the other two towers.

 > What kind of separation is needed  for 2 ele array?

Typically somewhere between 0.20 and 0.25 wavelength.  If they are
phased it is much easier if they are identical (otherwise one needs
unequal currents to account for the differences in height and
impedance).

73,

    ... Joe, W4TV


On 2018-09-27 5:01 PM, Edward via Topband wrote:
> Jon,
> 
> I have three crank-up towers spaced 35' apart. Tower #1 is 89' plus 20' mast, with some antenna top loading. Tower#2 is 70' crank up with 20' mast with minimal antenna too loading. Tower #3 is 106' crank with 20' mast plus top loading.
> 
> What kind of separation is needed  for 2 ele array?
> 
> Thanks,
> Ed NI6S
> 
>> On Sep 27, 2018, at 11:00 PM, Jon Zaimes <jz73 at verizon.net> wrote:
>>
>> Either crank up should work fine with adequate radial field.
>>
>> Inverted L may suffer from interaction with the towers.
>>
>> Depending on tower spacing and orientation, you may be able to feed both in a 2-element array.
>>
>> 73/Jon AA1K
>> Www.aa1k.us
> 
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