[TowerTalk] OWA Yagis was 40m 4el KLM - replacing linear loading with coils

[sawyered at earthlink.net]

Rich.  Can’t comment on the STEPPIR.  However the performance degradation of the yagi as you discuss at the band edges should be unaffected by the OWA feed.  Its more a function of the element spacing decisions of the rest of the yagi.  Makes the Transmitter happy, but doesn’t change some of the F/B or Gain vs frequency curves of the traditional yagi I don’t believe.  More of an expert on OWAs might offer some additional guidance.

Ed  N1UR

-----Original Message-----
From: Richard (Rick) Karlquist <richard at karlquist.com> 
Sent: Thursday, April 30, 2020 8:07 PM
To: sawyered at earthlink.net; towertalk at contesting.com
Subject: Re: [TowerTalk] OWA Yagis was 40m 4el KLM - replacing linear loading with coils



On 4/30/2020 4:15 PM, sawyered at earthlink.net wrote:
> In my view, the discussion on OWA yagis is about the element count and 
> the

> I have all conventional yagis.  The 2:1 bandwidth of the my yagis are 
> 28000
> - 28750.  2100 - 21375.  14000 - 14300.  7000 - 7185.  The amp is at 
> full power up to 3L1 SWR.  And I have most of my runs using LDF5-50.  
> So in my opinion, for a given boom length, the trade of the OWA isn't 
> worth the gain loss outside the 2:1 edges of the band.  Especially 
> because I am almost never running in those sections of the band - where gain is most important.

Unfortunately, the pattern of a Yagi can go all to hell as you move away from the design center frequency, no matter what your ability of match it.  The "2:1 VSWR bandwidth" doesn't tell you much about how the pattern holds up across frequency.

I can easily illustrate this with my MonstIR.  If I set it up for the bottom end of 40, then drive it at the top end of the band, I can use the driven element tuning (independent of the parasitic elements) to somewhat mitigate the VSWR.  But the pattern degrades considerably and I lose several dB or more of gain.


> Like everything, there is no free lunch in engineering trade-offs.

At least in terms of performance ONLY, the SteppIR is a free lunch.
AFAIK, it beats anything else in terms of gain across the entire band, given a boom length and number of elements.  Yes, there are various non-performance tradeoffs, but a properly working one is tough to beat.  YMMV, but my MonstIR has worked perfectly for over
10 years.  BTW, the SteppIR driven element has an impedance of
22.2 ohms, and the loss in the transformer/balun is extremely low.  I measured in on a VNA before I put up the antenna.

There are alternate designs that emulate the SteppIR in a monobander by individually tuning the elements using various modalities, such as motor tuned or relay switched capacitors or inductors.  They produce similar results if properly implemented.

> Ed  N1UR
> 

Rick N6RK