Yes very much needed, depending on antenna heights ofcourse.
Forexample, I once had a 5/5 20m stack at 100/47 ft then it
wasn´t needed. My current 20m 5/5 stack is at 130/65 ft and
I couldn´t be without it. One example, during sun spot maximum
if 5/5 Yagis BIP it could be 15 dB down compared to a 4 el
Yagi at 70ft (on east coast USA) then when flipping to BOP
it could be 5 dB better at least.
73 Jim SM2EKM
PS: I remember VE3GK, it was a good fellow and a big signal.
-------------------------------------------------------------
Tim Duffy K3LR wrote:
> Hello John!
>
> Yes, BOP can be useful for high angle paths to Europe on 14 and 7 MHz.
> It is most useful in high sunspot years in the early afternoon.
>
> 73!
> Tim K3LR
>
> -----Original Message-----
> From: john@kk9a.com [mailto:john@kk9a.com]
> Sent: Monday, October 08, 2007 6:28 PM
> To: TOWERTALK@contesting.com
> Cc: Tim Duffy K3LR
> Subject: Re: [TowerTalk] VE3GK stacking drawing
>
> When do you find the BOP useful - is it useful for DX contest?
>
>
>
> To: towertalk@contesting.com>
> Subject: Re: [TowerTalk] VE3GK stacking drawing
> From: "Tim Duffy K3LR"
> Reply-to: k3lr@k3lr.com
> Date: Sun, 7 Oct 2007 23:38:40 -0500
> List-post: <mailto:towertalk@contesting.com>
>
> Hello Stein!
>
> Starting on page 130 of Volume 7 of the ARRL Antenna Compendium shows the
> mono band stacking schematics I use. They are built from 1/4 wave sections
> of RG213, RG11 and RG83. The book is available from the ARRL.
>
> My two high stack switch design is simple using only RG-83 (35 ohm coaxial
> cable) to match 2 parallel 50 ohm loads and another 1/4 wavelength of RG213
> is used when feeding the single Yagi's so that the line length to the
> amplifier is not changed regardless of antenna selection. This keeps the
> VSWR at the same point which keeps the amplifier happy regardless of antenna
> combination.
>
> I also have a design that incorporates a both-out-of-phase (BOP) selection.
> This creates a high angle lobe. We use this feature on 40 and 20 meters.
>
> I use these designs for all of my 2,3 and 4 high stacked Yagi arrays.
>
> The secret to good Yagi monoband stacking is using exact ODD quarter
> wavelength feedlines (current forcing) to feed the individual Yagis.
>
> I would be happy to scan my two high design and email it to you if you like.
>
> 73!
> Tim K3LR
>
> http://www.k3lr.com
>
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