On 8/16/2011 3:16 PM, Dave Platt wrote:
In ,
Jeff wrote:

With the cardioid pattern, there's no ambiguity. With a deep null,
and a non-reflective environment, it's easy to use. However,
reflections off buildings and hills are a problem. The antenna is
roughly an omnidirectional antenna, and reflections will appear to
fill in the deep null. Not much can be done about that except to move
and try a different location. My favored method is by using a map.
Find a position, determine a bearing, and draw a line of position on
the map. Then, find a different location, and do it again. Repeat as
often as practical generating as many LOP's as possible.

I have seen recommendations that one do this by proceeding in a
straight line, taking bearings at positions of around 1/4 wavelength
or so. The effects of multipath will tend to cause the measured
bearing to wobble back and forth across an arc (as you go down the
line) and the true bearing will tend to be close to the center of that
arc.

I haven't tried this approach myself... but it might combine well with
your "take readings from lots of different locations" approach, by
helping cancel out some of the effects of multipath.


There's a photograph of this technique on a field with little flags at
different distances all oscillating around a single line illustrating it
in some ARRL publication (probably an antenna compendium, but maybe the
handbook or antenna book).