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Re: [TowerTalk] 40M rotary dipole and CM current

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 40M rotary dipole and CM current
From: Wes Stewart <wes_n7ws@triconet.org>
Date: Fri, 22 Sep 2017 05:31:07 -0700
List-post: <mailto:towertalk@contesting.com>
Yeah, but...

This thread started with a question about whether to just coil up some coax or to wind a balun at the feed point to "keep RF off the coax." This sounded like a valid transmitting concern to me.  It then morphed into something else completely when the salesmen for CM chokes hijacked it.

Wes  N7WS

On 9/21/2017 5:43 PM, Drew Vonada-Smith wrote:
Wes,

For transmit, yes.  The note below was with regards to receive.

Transmit CM issue - Unbalance of patterns, RF where it shouldn’t be, etc.

Receive CM issue:  Noise pickup from non-antenna sources.  Common example - 
noise from sources in your home heard loudly when antenna not pointed there.  
It's not because they are close to the radio, it can be because your cables 
pick them up and sends them around as CM.

We have to be careful what aspect we are talking about...

73,
Drew K3PA
------------------------------

Message: 2
Date: Thu, 21 Sep 2017 15:20:06 -0700
From: Wes Stewart <wes_n7ws@triconet.org>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 40M rotary dipole and CM current
Message-ID: <d9cfff41-03fa-9951-f48c-1607d735d133@triconet.org>
Content-Type: text/plain; charset=utf-8; format=flowed

I thought the CM current in question came from the antenna in the first place.

Wes? N7WS

On 9/21/2017 3:03 PM, Drew Vonada-Smith wrote:
Doug,

...

But, these common mode currents on the shield travel and radiate.  Therefore, 
they get to your antenna, and THEN they ARE on the center conductor.  You hear 
them.

73,
Drew K3PA



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