Hi Grant,
Treadmills are notorious RFI generators due to their variable speed
drives. I suspect you are onto something regarding what outlet it's
plugged into versus how long the run is relative to resonance. On my wifes
treadmill I had to add a choke on the power cord for common mode rejection,
as well as a commercial input power filter for differential mode
suppression. Here is a link to a youtube video showing my treadmill RFI
and the two filters I used.
I always knew when my old neighbor was on her treadmill, and had a lot of
fun telling her so.
73,
Don (wd98dsb)
On Fri, Jun 26, 2020 at 3:35 PM Grant Saviers <grants2@pacbell.net> wrote:
> Any surge protectors on the problem circuit? Degraded MOV's can cause
> problems. GFI outlets also.
>
> Grant KZ1W
>
> On 6/26/2020 10:30, Gary Peterson wrote:
> > Periodically, I have been plagued with RFI from an unknown source. It
> sounds like a washing machine, as far as the cadence is concerned, with a
> swish, swish, swish sound. It will show several tracks on the 80 meter
> waterfall. It will end abruptly. Every previous time it has come on, it
> has quit before I could get to my gear together and DF it. I had my
> equipment ready to go and when it came on and I dropped what I was doing
> and went outside. My loop gave me a beautiful, deep null toward the
> neighbors house, about 300 feet away.
> >
> > I gave my neighbor a call and told him what I discovered and asked him
> if he had been running any appliances a few minutes earlier. He told me
> his main squeeze had been on the treadmill. My neighbor is a ham, who has
> not been active for about a decade. He turned on the treadmill and there
> it was! Source found. The treadmill is a PowerTread, I was told.
> >
> > I gave him an EMI filter to try, that I had found in a box of assorted
> electronic parts purchased some time ago. The filter is a TDK, model
> ANF-106U. My neighbor plugged it into the outlet and plugged the treadmill
> into the EMI filter. The filter knocked the RFI down by a couple of S
> units, but I could still hear the swishing. Next, he plugged the
> treadmill, via an extension cord, into a different outlet, without the EMI
> filter. No interference whatsoever was heard or seen on the waterfall.
> >
> > Is it possible that the wiring from the nearest outlet, back to the
> service panel, is resonant on 80 meters? Or, is it more likely that a
> connection might need tightening in the outlet box or breaker panel? He
> does not know whether the troublesome outlet and the good outlet are on the
> same circuit or not. I had him check both outlets with an outlet tester,
> thinking that he might have a mis-wired outlet. Both checked OK. He is
> afraid to get into the troublesome outlet box or his electrical panel. I
> volunteered, but he doesn’t want me to take the risk. When I was in
> broadcasting full time, I was inside more electrical panels than I can
> count, but I respect his wishes. Before I hire a licensed electrician to
> check my neighbor’s wiring, I would like to have a better handle on the
> probable cause.
> >
> > Any thoughts as to the explanation for this rather odd behavior will be
> most appreciated.
> >
> > Gary, K0CX
> >
> > _______________________________________________
> > 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
>
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|