Well I thinking a little more simple than that. I was measuring RF current
into a telephone handset. (Remember those, before cordless. Kids that was
"Back in the day".) I plugged the filter into the cord at the wall, then I
plugged the filter at the phone and checked which reduced the RF current the
most. All of which can be done with a relative reading RF Meter.
Good information Jim. I especially like the part about the possibility of
turning the remaining wire into a half wave.
Mike
AD6AA
--- On Wed, 2/2/11, Jim Brown <jim@audiosystemsgroup.com> wrote:
> From: Jim Brown <jim@audiosystemsgroup.com>
> Subject: Re: [RFI] Clamp on RF meter
> To: rfi@contesting.com
> Date: Wednesday, February 2, 2011, 10:45 AM
> On 2/2/2011 10:26 AM, Michael Germino
> wrote:
> > I only used it if I have a problem. I used it to
> see where the best placement of the ferrite was.
> Sometimes where you think the placement is best, isn't.
>
> Not necessarily. Every wire (or conductor) is an antenna,
> whether we
> like it or not. A good ferrite choke acts like an open
> circuit, whereas
> a poor one (not enough turns) acts like an inductor,
> and one with too
> many turns can look capacitive. A choke simply ADDS its
> impedance in
> series with the existing antenna. If it's an optimum choke
> (near its
> resonance and a high impedance), it acts like an insulator
> to stop
> current AT THAT POIINT, but if the wire is long enough, the
> choke might
> turn the remaining wire into a half wave and increase the
> current in
> that part of the wire. Ditto with the choke that is L or C
> -- it simply
> shifts the current maxima and minima along that particular
> antenna.
>
> Bottom line -- measuring (or sensing) current in these
> conductors is
> certainly a worthwhile thing, but it's easy to
> mis-interpret the results
> if you don't view what you see in the light of the
> fundamental concepts
> of antennas.
>
> 73, Jim K9YC
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|