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October 30th 03, 07:56 AM

On 30 Oct 2003 06:27:42 GMT, (ARDUJENSKI) wrote:

Richard
I agree in that you need to chose either focusing on F/B or forward gain, just
like the YAGI. I guess from a practical point of view how is this accomplished?
I am not quite sure how far the field strength reading need to be to be of
value. I guess a little trial and error is in order here.

As you noted computers will get you in the ballpark but the real proof is in
actual testing which takes into account other variables.

I am a little surprised that there is not quite a bit of literature on this, or
at least not what I have found (tuning parasitics). Maybe some reading up on
the YAGI may help shed some light

As an aside I have worked on arrangements that do not employ radials such as
the inverted half square for 20 and 40m. This is where you have two 1/4wl
verticals elevated about 0.05wl and spaced about 1/2wl and the phasing line is
at the bottom vs the top. This enables you to have a rotatable half square and
get about 2 S-unit rejection off the ends (just like the calculations). The
nice thing is portability and not radial dependent. I got off the subject.

I wil try the strength meter at varying distances to see if it makes a
difference.

Thanks---Alan KB7MBI

Hi Alan,

Comparisons to yagis is intriguing, but likely going to be harder to
obtain equal results barring considerable ground development.
However, your comments about elevated structures brings back the
symmetry I discussed earlier and their equivalents. The relation of
director/reflector is bound to be a useful paradigm, and using tuning
to enforce that relationship would pay off. Just remember it is all
about phase; and phase is a product of both distance and electrical
delay within the resonant structures. These phase relationships are
more quickly experimented with in the computer to answer your question
about gain/F/B; but in all reality, with just two elements the F/B is
probably going to yield more dramatic results. In other words, the
best you will do by gain would be 3dB, but the F/B may easily find
10dB variation or more.

I think Roy's work on phasing antennas is in one of the ARRL Antenna
Compendiums and it should be sought as a source for you to reference
in these matters.

73's
Richard Clark, KB7QHC