On 4 Aug 2012 13:06:16 GMT, Allodoxaphobia
wrote:

I've yet to see anyone question the pattern/lobes/nulls
of the _transmitter_.

Good point. That may be the problem. I run into it all too often.
The WISP decides to use a very high gain omnidirectional antenna.
Something like 15dBi with an 8 degree vertical beam width. If your
house is at the exact same altitude as the WISP antenna, everything
works just great. However, if the house is at the same distance, but
at a different altitude, the house will be outside the antenna pattern
and you'll get little or no signal as most of it will be going
overhead.

Even worse, end fed colinear antennas tend to have some uptilt in the
pattern. A 15dBi omni (which incidentally is about 8ft long), might
have ALL the RF above the horizon if nothing is done about the uptilt.
If the house is below this omni antenna, you'll get very little
signal.

Ease of downtilting is one reason why WISP's use panel or sector
antennas with patterns like:
http://802.11junk.com/jeffl/antennas/AMOS-7/index.html
120 degree horizontal beamwidth. 8 degree vertical. 14dBi gain.
Three of these antennas, wrapped around a pole, pointed 8 degrees
downward, put all of the signal on the ground in a wide pattern, with
very little being lost sending RF above the horizon. Note the
adjustable downtilt:
http://www.qsl.net/yu1aw/ANT_VHF/Amos_Ant/3InvAmosa7c.JPG

Hint: If it doesn't work on paper, it's not going to work when
installed.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558