In the ARRL Antenna Book 21st and 22nd editions (and possibly other editions),
there is a section on optimized yagi designs for each band and at the end of
that there is a section titled “Modifying Monoband HyGain Yagis”. This
discusses the strategy HyGain took in their BA and CA designs, the CA being a
better design, but goes on to give dimensions that improve the F/R and SWR of
the CA design.
I have built a 105CA and now a 205CA to these dimensions. the 10M design worked
out nicely however (so far) we have not been able to obtain a good match /
resonance / SWR with the 205CA optimized design dimensions.
My question is this: If you have actually BUILT this antenna did you adjust
anything other than the Beta Match (such at tip lengths)? If so, what distance
did you set your Beta match (and / or tips)?
So far, we’ve pulled this antenna up to about 45’ probably 20 times or more
making gradual adjustments to the Beta Match but we get a 5:1 SWR across the
entire 20M band all the time. Tomorrow I’ll get the analyzer to see if there is
a resonance somewhere outside the band which will give me more to go on. This
was using the specified lengths / positions in the Optimized design. We’ve
checked and rechecked the dimensions and we are in very close agreement with
the measurements.
We were able to get an excellent 1.03 SWR with the antenna 5’ off the ground by
shortening the tips by 4” on each side and adjusting the Beta Match. So maybe I
don’t need a tower? Ha ha! Just kidding, this is exactly what the antenna
should be like at 5’ off the ground. The reason I mention this is that the
choke balun and feed line connections appear to be a-ok. We also tested the
feed and choke balun separately with open / short and 50 ohm loads. All looks
good.
I’m hoping someone has BUILT this antenna and got it tuned. I guess I’ll get it
eventually but so far nada…..
Tnx es 73!
Steve…. K3SW
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