[TowerTalk] Exploring another option re interaction 40/15 on

[StellarCAT]

Thanks Jim,

Yes - a rotating tower so all antennas are fixed to the tower

yes - the Optibeam and the F12 as well as the JK are all designed to play 
nice with a 15... M2 not so much.

The 80 is already turned to the tower to avoid issues with 20 (they WILL 
interact I'm told per Tom at F12) ... so the 26' T bars are in the plane of 
the 15 elements and 34' from the top one (but only 10' from the 20) ... by 
making the 40 90 degrees to the rest of the tower only its boom would impact 
the 15 or the 20.

That stated I am going to test this out - I have the test tower - I have 
both antennas - I'm going to put the 40 at 37' - the 15 6 element at 11' and 
range test it for FB with the 40 on axis and off ... compare and at least 
THEN I'll have some info on whether or not they play nice together.

Gary


-----Original Message----- 
From: Jim Thomson
Sent: Friday, June 3, 2016 1:43 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Exploring another option re interaction 40/15 on

Date: Fri, 3 Jun 2016 11:15:22 -0400
From: "StellarCAT" <rxdesign at ssvecnet.com>
To: "tower" <towertalk at contesting.com>
Subject: [TowerTalk] Exploring another option re interaction 40/15 on
same tower

Ok ... so the plan is to have 6/6 on 15M at 90/45 and I?m worried about (the 
unknown) interaction from a 4 el 40 mounted 34? above the top 15.

One option I have is to simply rotate the 40M 90 degrees and mount it that 
way. I already have the 80/75 dipole turned that way so the rotor has to 
have an ?offset? reading capability (Green Heron) ... so why not just 
?extend? that to 40 as well. I have a rugged mount that will allow it to be 
mounted on the 1.5? leg of the Rohn 45 with an arm that goes out to a second 
leg for added reinforcement ...

I don?t know if there is an adverse effect between 80 and 40 ? the 80 dipole 
is ~76? long with hi-Q coils at the center and 26? T bars out 2/3rd of the 
way to the end...

There might still be an issue of the boom of the 40, 42? long, interacting 
with the top 15 but it would be considerably less than the full antenna I?d 
guess... but only a guess.

does anyone have any issues with this? I know the wind load is going to be 
changed to put it lightly ... but with 6 antennas on this tower ? all 
substantial in size that might actually be a good thing making it less 
susceptible to the desire to ?point it in to the wind? (for as we all know 
we can?t always do that).

thoughts?

Gary
K9RX

##    Does the entire tower rotate ?   If so, just mount the 40m yagi 90 
degs to the pair of 15m yagis below it... problem solved.   The  42 ft boom 
of the 40m yagi will not screw
up the top 15m yagi..nor the lower 15m yagi.    If your  80m rotary dipole 
is  mounted so its  inline with the 40m boom, the 80m  will not affect the 
upper /lower 15M.
The  26 FT long  T bars  on the 80m   will now be  90 deg  from the  15M 
eles.... which is good.    Those  26 ft T bars will resonate around  18 
mhz....which might affect the top 15M array,
but that’s a moot point, since the T bars will be   90 degs to the 15M eles. 
( ditto with the 40M eles...also 90 degs to the 15M eles).

##  optibeam used 8 x stubs to detune their version of the 4 el 40M.   That 
plus their coils are not very far out from the boom.     F12 N type  40M 
eles  use LL rods,  but again,
they are not far out from the boom, only 7 ft 9 inch.  f12 didnt use any 
decoupling stubs..... however it resonates around 24 mhz... which will screw 
up a 12m  ant.... but solves the 40 + 15m interaction issue. ( without 
having to offset the booms  by 90 deg).

##  If ur sleeve idea works...and shifts the 3rd harmonic resonance up in 
freq a bunch.....( like way up..as in 24+ mhz)..... then u  wont have to 
rotate the  40 /15m booms by 90 deg.

##  If u have a top rotor for the 40 + 80....and side mount rotors for the 
pair of 15s... then  you might have to rotate the  80/40...but only when 
operating on 15m.   If ur sleeve ide works good, then u wont have to do 
that, and
everything can rotate independent of each other.

Jim   VE7RF