WD8DSB Elimination of treadmill RFI on 160 meters

For numerous years I have encountered approximately 15 db over S9 RFI on 160 meters that makes 160 meters useless when my wife uses our treadmill which is located in the basement and run on a dedicated 120 volt, 20 amp circuit. I previously tried using a common mode choke on the treadmill power cord with no noticeable improvement (14 turns of the power cord on a 2.4" OD Fair-Rite #31 mix toroid core (based on the K9YC hams guide to RFI document).

The treadmill is a Vision Fitness T9500 Deluxe and it has a 3 HP motor and uses PWM for motor control.

Today I decided to try a commercial power line filter that I had on hand that provides both differential and common mode filtering, and to my amazement the RFI was greatly reduced when using this filter by itself, and when used in combination with the common mode toroid choke filter mentioned above the RFI totally disappears. The commercial filter I used is a Delta 10DRCG5 filter that is only rated for 10 amps, and the treadmill full load rating is 20 amps so I did not run the treadmill at full speed during my tests but I did run it at speeds that my wife typically uses. I will now purchase the same style filter rated for 20 amps (model 20DRGG5) with hopes that it will be as effective as the 10 amp version when used in combination with the toroid choke filter.

Link to youtube video showing the effectiveness of the filters : http://www.youtube.com/watch?v=VO5DcVSw3M0

Picture of the common mode toroid choke filter (on the left), and the commercial power line filter (on the right) that were used together to eliminate my treadmill RFI. **** Note: ground (green) wire on both the load and line side of the Delta filter are attached to the frame (case) of this filter as shown in the second picture below. ****

Treadmill combination filter update (Jan 26, 2015).

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 this filter combination is knocking the signal down at least 46db (and probably more).

Picture of the common mode toroid choke filter (on the left), and the 20 amp dual stage commercial power line filter model 20DRGG5 manufactured by Delta (on the right) that were used together to eliminate my treadmill RFI.

Website created and maintained by Don Kirk (wd8dsb) Jan 8, 2015