One way to get control over the common mode current is to place a good common
mode choke between the tuner and the transceiver and let the tuner "float"
electrically. Don't ground the tuner and leave it far from any grounded
equipment. You don't stop the contribution from the feeder to the radiated
feild but you reduce the RF in the shack generated by the common mode current.
Hans - N2JFS
-----Original Message-----
From: Kelly Taylor <ve4xt@mymts.net>
To: Jon <kd5sfa@gmail.com>
Cc: towertalk <towertalk@contesting.com>; Mike Ryan <mryan001@tampabay.rr.com>
Sent: Fri, Dec 9, 2016 11:28 am
Subject: Re: [TowerTalk] OCF Dipole Questions
Setting aside the question of whether an OCF is a good design (I'll let K9YC
take that question), it's important to note that even if you could get a good
pattern off it (owing to feedline radiation), it would only behave like a
dipole at the frequency for which it's a half wavelength.
At higher frequencies, it will start to have more and more lobes as it
approaches a full wavelength.
If your friend experiences RF problems in the shack, its most likely because
the OCF is inherently unbalanced (it is fed off centre, after all) and it's
forcing common-mode current down the coax. A good choke is a must. And by good,
that usually means not store-bought.
73, kelly, ve4xt
Sent from my iPhone
> On Dec 8, 2016, at 17:49, Jon <kd5sfa@gmail.com> wrote:
>
> It should not matter which end is connected to the tree or tower as long as
> they are insulated from them.
>
>
> Where does it make best sense for the feedline to connect and be supported?
>
> I have mine offset from the tower with a fiberglass pole about 5 feet with
> the feedpoint at the apex and run it as an inverted V with no problems.
> This way the weight of the feedline is supported by the tower.
>
> The apex of mine is about 55' up.
>
> If installed flat it would likely be as directional as a standard dipole as
> far as I know.
>
>> On Thu, Dec 8, 2016 at 16:13 Mike Ryan <mryan001@tampabay.rr.com> wrote:
>>
>> A local here is about to put an offset center fed dipole up in the air. I
>>
>> think this antenna claims to work 10-80m. This is most likely going to be
>>
>> in the 40-45ft high range at best. A couple of questions came to mind when
>>
>> he mentioned that this was going to go up.
>>
>>
>>
>> If one end is in a tree, the other off a tower or some other support
>>
>> structure such as a tower, WHICH end would be in the tree..the SHORTER
>>
>> section or the LONGER section.does it matter?..(should the short end be in
>>
>> the tree or the long end?) .again, does it matter?
>>
>>
>>
>> The manufacturer had recommended the antenna be installed FLAT and not as
>> an
>>
>> inverted vee. At the aforementioned height, should this make a difference?
>>
>>
>>
>> At the aforementioned height, will the antenna have broadside properties or
>>
>> more unidirectional?
>>
>>
>>
>> Start the flames.thanks for reading in any event. - Mike
>>
>>
>>
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>>
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>>
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>>
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