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Re: [TowerTalk] Min spacing to 80m yagi ?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Min spacing to 80m yagi ?
From: GALE STEWARD <k3nd@yahoo.com>
Date: Wed, 6 Oct 2010 13:20:10 -0700 (PDT)
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
As K4WJ pointed out the 3.5mhz to 14mhz is actually 4X (not 3X) in frequency. 

That's what I get for too much multi-tasking!

73, Stew...




--- On Wed, 10/6/10, GALE STEWARD <k3nd@yahoo.com> wrote:

> From: GALE STEWARD <k3nd@yahoo.com>
> Subject: Re: [TowerTalk] Min spacing to 80m yagi ?
> To: towertalk@contesting.com
> Date: Wednesday, October 6, 2010, 11:55 AM
> I also think you would have problems.
> Some years ago we tried a 5el 15M about 8ft above a 2el 40
> (full length elements). The 40 worked fine but the 5el 15
> was almost useless - higher VSWR, gain & FB both
> severely degraded. Replacing the 15 with a 5el 10M yagi and
> both antennas performed well. 
> 
> The harmonic relationship between 40 & 15 has always
> been a problem if the antennas are too close. The ratio
> between 40/15 (7mhz X 3 = 21mhz) and 80/20 is the same
> (3.5mhz X 3 = 14mhz).
> 
> I think that the 20M will have real problems in this case.
> 
> YMMV!
> 
> 73, Stew K3ND
> 
> 
> 
> --- On Wed, 10/6/10, TexasRF@aol.com
> <TexasRF@aol.com>
> wrote:
> 
> > From: TexasRF@aol.com
> <TexasRF@aol.com>
> > Subject: Re: [TowerTalk] Min spacing to 80m yagi ?
> > To: jim.thom@telus.net,
> towertalk@contesting.com
> > Date: Wednesday, October 6, 2010, 8:48 AM
> > Jim, wouldn't you think that the 20m
> > yagi would suffer pattern degradation  
> > while the 80m yagi would be ok?
>
> > 73,
> > Gerald K5GW
>
>
>
>
> > In a message dated 10/6/2010 7:35:00 A.M. Central
> Daylight
> > Time,  
> > jim.thom@telus.net
> > writes:
> > 
> > How  close can you get a 20m yagi, below a 2-el 
> > 80m yagi ? 
> > I have an  option to use a F-12  Sigma 
> > 280-S  shortened 80m yagi
> > at  the top of the mast, with the F-12 
> > 340N  at the bottom of the mast.  
> > Spacing between the two of them would be  10.5' 
> >   If  possible,  I 
> > would like to sandwich my  F-12 
> > 520   [20m yagi]  between the 
> > 80 and 40m yagi.    Apparently, you  can
> > mount any other F-12 HF
> > yagi within 36"  of the 3-el  340N 
> > yagi.    If I put the 20m yagi
> > 4'  above the 40m yagi...  that would leave 
> > 6.5' between the 20m yagi
> > and the 80m  yagi.   Will this work
> > ??    If it doesn't, one option  is
> > to remove the 20m yagi.   Another option
> > is  to   place the 80 and 40m
> > yagi's at right angles to each other [ no 20m yagi
> at 
> > all] .   I don't 
> > think this
> > is required, but would minimize the  total wind
> load.
> > 
> > 
> > Plan B  would be to replace the 2-el 80m yagi 
> > with a
> > 80m rotary dipole...with dipole inline with 20m/40m
> > booms   below it.  IE: 
> > dipole
> > is then at right angles to both yagi's below 
> > it.   Due to  day time height 
> > restrictions,
> > the above  options are strictly an after dark
> > scenario.   I don't have any  
> > software on hand
> > to model any of the above.
> > 
> > Thanks....  Jim   VE7RF
> > 
> > 
> > 
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> > 
> 
> 
>       
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> 
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