[TowerTalk] Symptoms of antenna interaction?

[W0MU Mike Fatchett]

Do you need to be careful when turning antenna 90 degrees that your boom 
is not a fundamental length of the band you are concerned about or you 
might create other pattern issues?

W0MU

On 3/23/2021 9:08 PM, David Propper wrote:
> Al,
>
> I have had a 6 mtr beam mounted above my TA-33 tribander in several different installations for the past 40 plus years.  There has been no significant interaction between the two antennas (50 MHZ DXCC and WAS/WAC are the proof…………DXCC Honor Roll on HF as well, all antennas never higher than 45 feet).  The 6 mtr beam has been either a 4 or 5 element beam on a 12 foot boom.  My rule of thumb has always been to mount the 6 mtr beam 5 feet above the tribander.  If you need to mount the two meter beam on the tower, you could follow Chuck’s recommendation below or extend the mast by coupling a smaller diameter mast to the top of your existing mast.  The two mtr beam has minimal wind loading, so shifting down to a smaller diameter mast coupled to your main mast would be ok for the 7 element beam.
>
> FYI, when you mentioned that you tuned the antenna on the ground, just how close to the ground was the antenna ? Was it in a horizontal plane, or was it tuned on the tower and the tower folded over, so that either a director or reflector was close to the ground ?
>
> Good luck and hope to hear you on 6 mtrs once the Sporadic E season starts.
>
> 73,
> Dave, K2DP
> St. Louis, MO
>
>
>
>> On Mar 23, 2021, at 6:00 PM, Chuck Dietz <w5prchuck at gmail.com> wrote:
>>
>> Try the 6m perpendicular to the C3 to see if that helps. It could be placed
>> at the top of the mast for best separation and the 2m in the middle.
>>
>> Chuck W5PR
>>
>> On Tue, Mar 23, 2021 at 2:30 PM Al Kozakiewicz <akozak at hourglass.com> wrote:
>>
>>> Still have a foot of snow on the ground, so I'm not quite ready to climb
>>> yet.
>>>
>>> See photos on QRZ page.
>>>
>>> I have 3 antennas on a 10' mast sticking a total of 8' out the top of the
>>> tower. From top to bottom, 2M7, 6M3 and a C3, all equally spaced.  All were
>>> tuned to resonance on the ground.
>>>
>>> Now up in the air, the C3 and 2M7 are fine, but the 6M3 is useless. The
>>> SWR is about 3:1 and Z=~70 ohms at the minimum for both.
>>>
>>> Is this symptomatic of interaction, i.e. feed point characteristics change
>>> while resonance frequency remains the same? If so, what is a recommended
>>> solution? The one possibility I haven't checked yet as it requires climbing
>>> is a bad rotor loop cable.
>>>
>>> Al
>>> AB2ZY
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