Topband: Elimination of Treadmill RFI on 160 meters

[Brad Rehm]

Don,

FWIW, today, W5UJE and I dealt with a treadmill problem similar to yours by
installing a commercial line filter between the line and the treadmill
electronics.  A Corcom/TE Connectivity 20VR1 filter reduced the 40m and 75m
noise at his receiver from S9+10db to less than S2 (his noise floor this
morning).  The 20 Amp rating was needed because the manufacturer's
published current requirement for the treadmill was 15 Amps.

In measurements we'd made earlier, we found that this was a common-mode
problem and that the noise spurs were about 20 kHz apart when the treadmill
was operating under a moderate load.  The spectrum scope on his radio
showed 20 kHz-spaced broadband noise up through 29 MHz, peaking between 1.8
and 15 MHz.  The line filter we chose offers 10-20 dB of supperssion below
50 kHz and 60-80 dB of suppression between 300 kHz and 29 MHz.  No
additional filtering with torroids or capacitors was needed.

In other words, our results were similar to yours, and one wonders how
manufacturers can say these things meet Part 15 requirements for conducted
emissions.

Brad  KV5V

On Mon, Jan 26, 2015 at 7:22 PM, Don Kirk <wd8dsb at gmail.com> wrote:

> Treadmill combination filter update.
>
> Today I replaced the 10 amp commercial filter with the 20 amp version of
> the filter, and the results are similar.  Below are a few measurements on
> 160 meters and 80 meters showing how effective the combination of the two
> filters are (14 turn toroid choke, and commercial filter model 20DRGG5 made
> by Delta) in reducing my treadmill RFI.
>
> *1.8068 Mhz*
> No Filters : 19db over S9
> With Filters : S7 which is my noise floor
>
> *1.8291 Mhz*
> No Filters : 15db over S9
> With Filters : S7 which is my noise floor
>
> *3.5250 Mhz*
> No Filters : 28db over S9
> With Filters : S6 which is my noise floor
>
>
> *3.5475 Mhz*
> No Filters : 25db over S9
> With Filters : S6 which is my noise floor
>
> The 3.5250 Mhz readings indicate the filter is knocking the signal down at
> least 46db (and probably more).
>
> 73,
> Don (wd8dsb)
>
>