[TowerTalk] HyGain 205CA OPTIMIZED
john at kk9a.com
john at kk9a.com
Fri Jun 28 20:29:41 EDT 2019
I have no experience with this antenna however something sounds very
wrong connectionwise, Even Hy-Gain beams with broken parasitic element
tips have a better SWR:) If the coax and element connections are
indeed OK, finding the correct match/DE settings without some type of
analyzer is a crapshoot. Back when I designed Yagis with hairpins on
YO/AO, I used coax that was 1/2wl multiples and an analyzer so I knew
the actual measured impedance and resonant frequency. It was a bit of
a pain to adjust because the element length and the hairpin length
effect each other and I usually did this work solo. I am so glad that
I switched to OWA antennas where it might take one minor DE adjustment
to have nearly perfect SWR across the band. BTW, also make sure that
you are raising it in a clear area when testing.
Steve Walters K4IKM wrote:
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
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!
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