[TowerTalk] dipole question

[Al Williams]

Thanks for the response.  Actually I put this posting in my outbox thinking 
that I could at a later time edit  it for a more clear posting, but 
apparently the outbox is the place to hold things for later sending!  Sorry.


----- Original Message ----- 
From: "David Robbins K1TTT" <k1ttt at arrl.net>
To: "reflector -tower" <towertalk at contesting.com>
Sent: Friday, July 22, 2005 11:42 AM
Subject: Re: [TowerTalk] dipole question


> Its not really a loss.  It is current that would otherwise be on the other
> side of the dipole.  The problem with it is:
> 1. it takes away from the desired pattern
> 2. is often the wrong polarization
> 3. adds lobes where there shouldn't be in the pattern
> 4. and worst of all, brings rf closer to or even back into the shack or
> house and since it is much closer than the rest of the antenna can easily
> cause tvi and other nasty problems like rf burns.
> 5. and just the opposite on rx, it picks up rf from surrounding devices it
> is close to and couples that into the antenna adding to rx noise.
>
>
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
>>
>> -----Original Message-----
>> From: towertalk-bounces at contesting.com [mailto:towertalk-
>> bounces at contesting.com] On Behalf Of Al Williams
>> Sent: Friday, July 22, 2005 16:15
>> To: TOWERTALK at contesting.com
>> Subject: Re: [TowerTalk] dipole question
>>
>>
>> ----- Original Message -----
>> From: "Tom Rauch" <w8ji at contesting.com>
>> Sent: Wednesday, July 20, 2005 3:56 AM
>> >
>> > Since you attach the
>> > grounded shield to one half, the outside of the cable
>> > elevates in voltage in an attempt to get current flowing in
>> > the grounded half of the dipole. That causes some current to
>> > flow down the outside of the shield, and the cable to
>> > radiate. The outside of the shield actually becomes part of
>> > the antenna when the feedpoint isn't properly designed!
>> >
>> > > It actually is a bit more complex than this, but this is a
>> > good rough idea of what is happening.
>> >
>> I appreciate the explanation given, but (I and maybe others) would like a
>> follow-on of what is happening to this outside-of-the-shield current and
>> how
>> significant is it?
>>
>> 2. The current flowing on the outside of the shield must have an opposite
>> current (charge) flowing somewhere.  Is it the portion of the antenna 
>> that
>> is connected to the center conductor.
>>
>> 1. If for example, 100 watts is output but 10 watts is diverted to the
>> outside, that still leaves 90 watts to the intended antenna--an
>> insignificant (?) loss.
>>
>> 3.
>>
>> _______________________________________________
>>
>> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
>> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with
>> any questions and ask for Sherman, W2FLA.
>>
>> _______________________________________________
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>> http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
> any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>