[RFI] Ladder Line and RFI/Noise

[Michael Coslo]

On Oct 19, 2010, at 2:48 PM, Rick Karlquist wrote:

> Jim Brown wrote:
>> This discussion applies to differential coupling. There's also common
>> mode coupling, of course, and antennas fed with ladder line rarely have
>> a common mode choke. But they NEED a common mode choke, because nearly
>> all ham antennas have at least SOME unbalance by virtue of asymmetry in
>> their surroundings, their length, etc.  Yes, coax has more loss and it
> 
> Then there is always the exception to the rule:
> 
> I use common mode chokes at both ends of my open wire line.
> It never occurred to me to build it any other way.
> Maybe that is why I don't have any trouble with it picking up
> noise.


I certainly don't want to be contrary, but I think that the coax good vs ladder line bad case is overstated a bit. I live in a residential neighborhood, the neighbors are 25 feet on either side of us, and yet my dipole fed with ladder line has performed well for me, doesn't radiate in the shack, doesn't pick up noise from the neighbors or give them any noise problems - no complaints anyhow. I've used a similar coax fed antenna with similar results.

- 73 de Mike N3LI -