Stacking TH-7 & TH-5

[Tony Brock-Fisher]

I'd have a couple of concerns about what you proposed on stacking
the TH-7, TH-5, and TH-3 as follows, Larry:

1. Stacking works because signals arriving at the two antennas add in
phase and are of approximately the same strength. Noise arriving from
directions other than the desired one is out of phase on the two
antennas and doesn't sum the way the desired signals do. 

2. Different antennas have a different phase relationship between
the incoming signals and the resultant voltage on the feedline.
Therefore simply phasing different antennas with equal length
coax does not guarantee phase alignment. It may work, or it
may have a maximum gain at some awful elevation angle.

3. The signal strength from the two antennas needs to be close
to equal, or the net gain is not worth the trouble. I'd really
suspect that the signal strength from a TH-3 at low height
will be well below that of the TH-5 or TH-7 above it.

My advice - trade the TH-5 and TH-3 for another TH-7 and
phase the pair of like antennas.

-Tony, K1KP, fisher@hp-and2.an.hp.com