You might consider these as a two band fan dipole fed at a common
point. If the tip of the 30m was 24 to 30" from the 40m that reduces
the interaction, but modeling is still advised. Make a mast/antenna
mounting plate that has one tips up and one tips down.
See ac6la.com for advice about modeling a fan.
Grant KZ1W
On 7/15/2018 20:43 PM, john@kk9a.com wrote:
I am not familiar with MMANA but this is quite easy to model using EZNEC.
There is no need to model your exact tubing diameters, certainly there must
be a dipole example that you can alter. I doubt that there will be much
interaction. What else is on the mast?
John KK9A
To: towertalk reflector <towertalk@contesting.com>
Subject: [TowerTalk] 40/30 antennas on same mast
From: N1BUG <paul@n1bug.com>
Date: Sun, 15 Jul 2018 21:06:11 -0400
I have been trying to model this (using MMANA) but I have a hard
time getting my head around modeling.
I have a full size 40 meter rotatable dipole which I plan to install
at 105 feet.
I want to put 30 meters on the same mast if possible. I had
considered two options but am not sure if there will be problems
with either or both.
Option 1 would be to add a 30 meter element to the existing 40 meter
rotatable dipole, making two parallel elements with one a few inches
above or below the other, common feed. I am not certain how well
this works on bands that are not widely separated in frequency.
Option 2 would be to put a full size 30 meter rotatable dipole
higher on the mast. The maximum achievable vertical separation would
be 10 feet with 40 meters at 105 feet and 30 meters at 115 feet. I
am not convinced this won't become a two element beam pointing
straight up!
Has anyone modeled these or similar configurations?
Thanks,
Paul N1BUG
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