[TowerTalk] 40M rotary dipole and CM current

Joe Subich, W4TV lists at subich.com
Thu Sep 21 21:07:45 EDT 2017


> As I've tried to emphasize, the most important reason for using a
> choke is to suppress RX noise, but by suppressing common mode current
> during TX, we minimize crosstalk to other antennas.
By suppressing common mode current in TX you prevent the "random radial"
phenomenon.  In doing so, you mitigate the "pin 1" problem by reducing
the RF voltage on equipment cases/connecting cables and avoid issues
of a "biting mic" (if you're old enough to remember RF burns to the lips
from the case of a D-104).

73,

    ... Joe, W4TV


On 9/21/2017 8:26 PM, Jim Brown wrote:
> On 9/21/2017 3:20 PM, Wes Stewart wrote:
>> I thought the CM current in question came from the antenna in the 
>> first place.
> 
> It depends whether it's receive or transmit. The principle of 
> reciprocity applies. As I've tried to emphasize, the most important 
> reason for using a choke is to suppress RX noise, but by suppressing 
> common mode current during TX, we minimize crosstalk to other antennas.
> 
> 73, Jim K9YC
> 
> 


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