Topband: Elimination of Treadmill RFI on 160 meters

[Brad Rehm]

Yes.  Remember, the test is conducted with the EUT taped to a grounded
copper plate on the table top.  The LISN is taped to a grounded plate on
the floor of the test chamber.  This is not how we set up and use equipment
in our homes.

Like many compliance tests, this one is accepted as "sufficient" to allow
us to measure emissions.  My experience this morning shows that in some
cases it is sufficient.  Don's experience shows it may not be in others.
In any case, I think there's a good chance both of these treadmills would
fail a CE re-test.

Brad

On Tue, Jan 27, 2015 at 6:08 PM, Tom W8JI <w8ji at w8ji.com> wrote:

> are talking about current that is flowing in the same direction on three
>> conductors."  In my case the additional Toroid core choke had a very
>> noticeable impact, and I now can't tell when the treadmill is on when
>> using
>> the combination of both filters.
>>
>> P.S. I sent an e-mail to the manufacturer of our Treadmill, and they never
>> responded.  I am now going to call them on the phone in an attempt to get
>> in touch with their design engineers, and likely will also file a
>> complaint
>> with the FCC regarding treadmills in general.  There are a couple more
>> treadmills near my home that generate very strong RFI, but fortunately
>> they
>> normally use their Treadmills during the day, and I operate mostly at
>> night.
>>
>
> The FCC requires testing of power line conducted emissions with a line
> sample unit that connects from each conductor to ground. One LISN is
> specified to go from each current-carrying conductor to ground. The safety
> ground, since it does not carry current, is grounded.
>
> The flaw in this system is that differential voltages between current
> carrying wires are not measured, and anything on the safety ground isn't
> measured.  Noise voltage is only measured from individual current carrying
> conductors to ground, and the safety ground is grounded and not measured.
>
> Filters inside devices and many outside filters often route the noise
> right out on the safety ground, in differential to the equipment case (if
> large it acts like a groundplane) or other connecting wired systems like a
> Telco line or data interface cable.
>
> Since the FCC mandates the safety ground and other grounds be grounded to
> the test equipment RF measurement groundplane, that path or ground loop
> paths are not measured. This allows some pretty ratty stuff to pass FCC
> tests.
>
> The FCC should have created a better test, instead of assuming all grounds
> in the real world were common-connected with near zero impedance.
>
> 73 Tom
>