"Ken" wrote in message
news
I am building the Ramsey Electronics DDF-1 doppler DF. This uses
four 1/4 wave whip antennas on the corners of a square approximately
1/4 wavelength on a side. These are connected to a rooftop switcher
that activates each antenna in sequence. See:

http://www.ramseyelectronics.com/cgi...ction&key=DDF1

My question is, How dependent is this rig on proper whip length to
function properly? Does sensitivity suffer if my whips are
significantly too short, or does the thing simply stop working
properly?

I want to use it for 6M. I have the room for the 55" antenna spacing,
but my antennas are only around 24" long.


shorter whips would reduce sensitivity, just as they would for a simple
receiver. the whip spacing can also be reduced, it will just reduce the
direction detection sensitivity as the spacing shrinks. one important thing
is that you don't want to use one that is spaced for 6m on a higher
frequency band... if the spacing gets too much more than 1/4 wave or
approaches 1/2 wave the detector may not respond properly and the direction
indication could be unstable or 180 out from where it should be.