[TowerTalk] HyGain 205CA OPTIMIZED

[john at kk9a.com]

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.

John KK9A




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  
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