Re-posted.
Would a coax fed dipole then be less likely to pick up this sort of
noise than say a center fed doublet with open wire feed?
This is the only group I have to do a "reply to all". Sorry Tom. I
didn't mean it just for you.
On 21, Nov 2006, at 18:00, Tom Rauch wrote:
>> I think the idea is that if the supply and return from the
>> dimmer to the lamp are essentially a pair, then the
>> magnetic fields cancel, and it's sort of self shielding (a
>> balanced pair), since they are right next to each other,
>> and the "loop area" is small.
>
> They are always the same distance apart, assuming the wire
> is the same wire.
>
> Perhaps the assumption is the RFI is caused by differential
> currents, but in most cases for us they are either common
> mode or turn into common mode elesewhere in the system and
> radiate to the receiving antenna. If someone's antenna is
> not the primary source of ingress, they need to work on that
> first. We all know RFI is a lot different than ingress into
> audio systems, and audio systems are where sharing common
> outlets is a big problem.
>
>> A shared neutral has more potential for having the supply
>> and return form a loop with some area, and making a better
>> radiator.
>
> BPL advocates seem to think RF won't radiate from power
> lines with single returns also. Any line excited with RF
> currents will be a problem because eventually it will become
> unbalanced no matter how it is wired. In my experience
> worrying about wire routing is largely a waste of time when
> dealing with radio frequencies. Audio is another story, but
> again it is best handled by proper interconnects in audio
> lines.
>
> If you excite anything other than a real transmission line
> that is properly installed, terminated (for balance), and
> fed.... it will radiate. And that is how things get into our
> receivers unless our stations happen to be messed up. For
> example people use longwire or other Marconi antennas with
> less than perfect grounds, and the power lines become part
> of the ground system. This allows ingress by "pumping" the
> ground with noise. In a case like this the antenna should be
> fixed. The same is true for Windoms or OCF dipoles or even
> regular dipoles without baluns.
>
> The fact is we can run wires anyway we want through the
> house, and if a trashy device is connected to the line we
> will hear it. The system is so messed up it's pure dumb luck
> if a wiring change makes it better or worse.
>
> The only sure cure is to make sure the antenna and feedline
> have minimal response to noise on house wiring, and make
> sure the things in our houses don't generate RFI. I sure
> wouldn't go rewiring anything to try to cure noise!
>
> 73 Tom
>
>
>
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