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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