Mike,
I plan to make YouTube video about this, but did you read the modelling section
of my 80-40m Yagi paper?
Perhaps that is exactly the message in the bottle if you are looking for?
https://drive.google.com/file/d/1IksvND0LfeSBcH6j7UEWkyjkIvexDIgX/view
<https://drive.google.com/file/d/1IksvND0LfeSBcH6j7UEWkyjkIvexDIgX/view>
There I show and explain the relationship between driver tuning relative to the
parasitic tuning and effect on SWR bandwidth.
Also, I really think this particular video I made is vital to understanding how
a 2 el Yagi works:
https://youtu.be/2DcvmGPLdT0 <https://youtu.be/2DcvmGPLdT0>
73, steve ve6wz
> On May 23, 2021, at 2:31 PM, Mike Zak <mike@brookblue.com> wrote:
>
> Is there a paper, article, YouTube video, Powerpoint deck, chapter in a book,
> website, message-in-a-bottle, or anything else, that clearly and succinctly
> describes the trade-offs and interactions between yagi gain, pattern, and
> match?
>
> A 15 minute session with EZNEC, and a candidate yagi design, is plenty
> adequate for showing that there’s some serious systems engineering involved
> in coming up with the right set of trade-offs, starting with “which problem
> are we trying to solve?” But few of us are ever going to capture the ideal
> design and then fabricate it. So maybe if there was some insight around
> these tradeoffs we could all do a better job with our selections of
> commercially available products.
>
> Did W4RNL ever do anything along these lines? Or W2PV? How about the Telrex
> archives? Anyone have any suggestions for something that is readable by mere
> mortals?
>
> Mike, W1MU
>
>
>
> From: TowerTalk <towertalk-bounces@contesting.com> on behalf of Jim Brown
> <jim@audiosystemsgroup.com>
> Reply-To: "jim@audiosystemsgroup.com" <jim@audiosystemsgroup.com>
> Date: Sunday, May 23, 2021 at 3:11 PM
> To: "towertalk@contesting.com" <towertalk@contesting.com>
> Subject: Re: [TowerTalk] OptiBeam OB2-40M
>
> YES! SWR is NOT an indicator of antenna performance.
>
> 73, Jim K9YC
>
> On 5/23/2021 9:40 AM, Richard (Rick) Karlquist wrote:
>
> On 5/23/2021 7:29 AM, VE6WZ_Steve wrote:
> I have received a few direct email questions about this thread…..
> Just to be clear, the reason for inductor switching at the Yagi
> elements is NOT only to get a “good, low SWR" match at the driver.
>
> The “SWR” and “matching” at the feedpoint is really NOT the issue.
>
> The real issue is tuning the REFLECTOR across the band. That is what
> determines the gain and F/B performance.
> The PARASITIC element needs to be incremented across the band to
> maintain maximum gain and F/B performance.
>
> Yagi SWR has very little to do with performance.
>
> Steve, ve6wz
>
>
> Another great posting from Steve. It seems like this point
> has to be constantly repeated on TT to counteract marketing
> hype and wishful thinking. When I first got my MonstIR,
> I did some experiments where I set the tuning for 40 CW
> and then QSY'ed to 40 phone, without retuning the MonstIR.
> Of course the SWR went way up. I then used the custom
> tuning feature to tweak just the driven element for SWR.
> This did improve the VSWR somewhat, but the gain and F/B
> were still lousy. SWR bandwidth doesn't equal pattern
> bandwidth. And the MonstIR is a full size 3 element
> design (yes, 70 foot elements), so it will tend to do
> better than a shortened 2 element.
>
> Rick N6RK
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