[TowerTalk] Stacking offset compensation

[HA3LN]

Hi All,

HNY to All!

Seems my provider went for holidays too, got the replies only yesterday 
night in bulk.
(hope my address is not bouncing ;-)

Thanks a lot for the explanations and hints to All.
As ON4UN always said every tenths of a dB counts so trying to minimize 
the offset effect in the system. It will be difficult to measure the 
upper coax on the mast but will find a way to the closest estimate of 
the feeder length.

In the 10m case the offset is ~2 feet so just at the border but better 
to fix this as well.
Anyway, the stack usage will aim direction diversity as well as more 
gain into the US to utilize the next layer of stns for the WRTC 
qualification (and bigger fun).

John KK9A,
Actually great idea to pull back a bit the DE to line them up but due to 
the local wind "patterns" I'm not that brave to load the mast further. 
So will make the coax length play for equal electrical feed-lines.


I read in the archive that the excess feeder can be winded up without 
any negative impact.

Thanks a lot once again.

73!
Csaba  HA3LN / HG3N







On 2023-12-27 19:41, HA3LN wrote:
> Dear All,
> 
> Turning into the final stage lifting the stacks for 10m and 15m before 
> ARRL-DX contests
> I need a bit of guidance regarding the feed-line setup.
> 
> I read in the ARRL Antenna book that if 2x vertically stacked Yagi's
> are not exactly in the same vertical plane feed-line length compensation 
> is needed to avoid stacking performance degradation.
> 
> Both band setups will have similar OWA Yagi types via coax chokes + WX0B 
> like stackers.
> 
> However, due to the tower geometry it is not possible to position the 
> lower antennas to the proper vertical position "below" the upper one.
> 
> ...for 15m (crank-up tower), is OK to have the lower one "underneath" 
> the upper one but with a ~60cm offset to the side direction.
> ...for 10m (freestanding tower), not only the side ~80cm offset but due 
> to the element positions it needs to be pulled a bit back with ~80cm as 
> well. So in this case the offset is two dimensional.
> 
> - are these less than 1m offsets are serious enough the compensate (with 
> aiming for max performance)?
> - is it possible/needed to compensate the "side only" offset in 15m case 
> as the driven elements will be in vertically same plane?
> - these calculation formulas can be used to determine the extra coax 
> needed?
> (Driver element offset length) / WL x 360 = degrees of delay required
> (Driver element offset length) / VF = extra coax length required
> 
> 
> Thanks in advance.
> 
> 73!
> Csaba  HA3LN / HG3N
> 
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