[TowerTalk] [re: TowerTalk] 40/30 antennas on same mast

[Grant Saviers]

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 at 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 at contesting.com>
> Subject:	[TowerTalk] 40/30 antennas on same mast
> From:	N1BUG <paul at 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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