[TowerTalk] HyGain 205CA OPTIMIZED

Steve Maki lists at oakcom.org
Fri Jun 28 23:05:56 EDT 2019

I agree with KQ2M that there probably is an intermittent someplace in 
order for such a large change to occur, even though it's a given that 
measurements at 5' aren't very predictive. Put the Beta match where the 
manual says and track down what's really wrong.

Not to get you on a completely different path, but a very nice 4L OWA on 
that 34' boom can be assembled without much effort. You throw away the 
beta match and one element (well store the element for spare parts). 
Adjust DE and D1 positions and lengths, and R & D2 lengths. You get 
virtually flat 1:1 VSWR across the band with NO tuning required. Similar 
gain as the 205CA. You give up some FB - it's around 17-18 DB across the 
band. I've been testing one here for a while and love it.

GL, Steve K8LX

On 06/28/19 16:28 PM, Steve Walters K4IKM via TowerTalk 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…..

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