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!
--- On Wed, 10/6/10, GALE STEWARD <firstname.lastname@example.org> wrote:
> From: GALE STEWARD <email@example.com>
> Subject: Re: [TowerTalk] Min spacing to 80m yagi ?
> To: firstname.lastname@example.org
> 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.
> 73, Stew K3ND
> --- On Wed, 10/6/10, TexasRF@aol.com
> > From: TexasRF@aol.com
> > Subject: Re: [TowerTalk] Min spacing to 80m yagi ?
> > To: email@example.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
> > Time,
> > firstname.lastname@example.org
> > 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
> > all] . I don't
> > think this
> > is required, but would minimize the total wind
> > 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
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