OT: RF Choke question

[Terry]

I need some advice from someone with experience in dealing with RF problems.
I have an in-home elevator that is putting out RF hash in harmonic locations
on the ham bands, especially 80 meters.  I've gotten tired of dealing with
the noise.  I have both a 240V circuit and a 120V circuit feeding the
control panel.  The 120V circuit powers the cab lights and elevator
switches.  The 240 feeds the motors the raise and lower the elevator.  The
cab is 3 ft. by 4 ft. so it isn't a small residential elevator.  We had our
house designed for it when we built two years ago.

 

I have two 4 in. inside diameter RF toroid chokes that I bought specifically
for the ham bands.  I plan on putting these RF chokes on the electrical
supply lines for each circuit right before they enter the control panel to
see if it helps my RF issue.  I have two questions.

 

1. Is rapping 10 turns of the electrical wires of each circuit around
the toroid enough?

 

2. The electrical wires are individually connected to the control
panel.  In the case of the 120V, there is a white, black, and ground.  In
the case of the 240, there is 3 reds, a black and a ground.  Do I have to
wrap the ground wires of these circuits around the toroid as I do the other
electrical wires?

 

It will be interesting to see how much better my K4 will be when I get it,
in rejecting RF noise, compared to my KX2, KX3, and K2.  

 

Thanks and 73,

 

Terry, N7TB

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[Jim Brown-10]

On 7/2/2020 9:54 AM, Terry Brown wrote:
> 1. Is rapping 10 turns of the electrical wires of each circuit around
> the toroid enough?

Use the recommendations in  http://k9yc.com/2018Cookbook.pdf as a
starting point, and study k9yc.com/RFI-Ham.pdf to understand concepts.
>
>  
>
> 2. The electrical wires are individually connected to the control
> panel.  In the case of the 120V, there is a white, black, and ground.  In
> the case of the 240, there is 3 reds, a black and a ground.  Do I have to
> wrap the ground wires of these circuits around the toroid as I do the other
> electrical wires?

ALL conductors must be wound around the ferrite. Chokes must be right at
the noise source (the elevator motor's variable speed control
electronics), NOT near the panel. Choke both the AC line side and the
wiring between the motor's controller and the motor.

Also, make sure that the green wire between the AC line and the motor is
the only ground for the elevator.

If possible, make all wiring associated with the elevator twisted
triplet (for 120V or pure 240V) and twisted 4-conductor for combined
120/240V wiring.

73, Jim K9YC

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