[TowerTalk] "Small pistol" contesting station- how many tribanders and how high?

[Michael Keane K1MK]

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 at alum.mit.edu