At 01:57 PM 3/13/07, Rudy Bakalov wrote:
>I am planning my "small pistol" contesting station that I will build
>next year. After reading tons of books and articles on antennas, I
>believe I do want to stack tribanders to cover for the most likely
>angles of arriving signals.
>
> I have some very specific questions, though:
>
> 1. Assuming flat terrain, do I have to run HFTA analysis or there
> are some "generic" rules of thumb I can use for stacking- say 60/90
> or 70/100? I plan on having a single 90' tower.
One rule of thumb for stacking two antennas is H and H/2. With two
tri-banders on a 90' tower, that's likely to be too wide a spacing on 10m.
So a fall back rule of thumb is 30' to 40' spacing is usually a good
compromise with tri-banders.
For a more definitive answer than that, run HFTA.
> 2. Do I need to calculate arriving angles for my specific
> location (45N, 79W) or can use existing data?
No. The data computed by Dean N6BV in the ARRL Antenna Book is more
than sufficient.
> 3. Assuming buying stacking gizmos from Array Solutions to make
> my life easier, do you anticipate any problems due to stacking
> different antennas- C31XR on the top and 4el SteppIR at the bottom
> (will take care of 80 and 40 m by using phased dual-band verticals)?
Feeding that combination may be tricky. With the open sleeve feed on
the C31XR, you'll probably have a different zero phase offset for
each band. How big an effect that is and how much a compromise
feeding with the same length line on all three bands wpild be, you'll
have to model.
73,
Mike K1MK
Michael Keane K1MK
k1mk@alum.mit.edu
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