On Jan 2, 12:45*pm, Richard Clark wrote:
On Sat, 2 Jan 2010 09:08:16 -0800 (PST), mr1956
wrote:

I suppose my question is this: Is there a longer multiple of
wavelength I can use for the impedance matching 75 ohm sections to
develop a more practical design for what I need? Or, am I stuck with
the 2.1" length due to the frequency?

Hi Curt,

To answer your last question first: you can use odd multiples (1, 3,
5, 7...) if your initial computation was correct. *Consider, if your
computation contains errors, they, too, will multiply.

Computations aside, a receiver rarely needs exact matching when "close
is good enough." *Two 50 Ohm antennas in parallel or series are not
seriously off. *The mismatch loss would probably amount to less than 1
dB whereas your using two crossed antennas is in an effort to recover
from the loss of polarization mismatch that can exceed 20 to 30 dB.

As a practical matter, have you tried testing these antenna issues at
ground level? *There are certainly complications that ground proximity
can introduce (reflection from ground being principle among them). *As
a first pass approximation, however, you can come to some feeling for
many issues without having to loft anything into the air. *Insofar as
polarization mismatch goes, ground's proximity would tend to dilute my
suggestion as ground and anything that is in proximity would tend to
offer many reflections some of which don't come anywhere near your
final application.

73's
Richard Clark, KB7QHC

Richard:

Yes I have tried testing one of the antennas at ground level but that
is not really representative of the reality. I suppose the bottom line
for me, is that how much of a loss and I looking at if I simply hook
these two 50 ohm antennas in parallel to a tee section, then on to the
receiver? The whole reason to have the two yagis to begin with is to
increase overall gain and insure that the polarization between the
transmitting and receiving antennas is good enough to maintain a link.

If I elect to do a multiple of 1/4 wave, then how does that work out
with the formula regarding frequency?

Thanks,

Curt Newport