[RFI] Motors/controllers and something to think about

myles landstein myles.landstein at gmail.com
Thu Aug 16 02:04:11 PDT 2012

You are very correct.  Maybe 4yrs ago my co op which consists of about 15 buildings in a few block radius upgraded its original elevator systems.

The originals were just  relay racks and motors, most were dated back to 1960s and were in mint condition. The law here mandated replacement.

The new system throws out wide-band RF  mostly from 1 to 18mhz at S9+ and slightly less from 18-54mhz.

I checked the equipment, and as Roger stated it was now based on a PWM unit.  Specifically a Magnatek 600 motor controller.  I measured all the components and found that inside the cabinet just that unit itself is radiating  the cables etc are mostly clean.  So the power lines in/out data lines  etc  no problems.

Contacted the company that makes that  specific part and their answer was " we have a Canadian certification, which is higher, so we don't need an FCC cert.

Obviously, I am not a lawyer but I presume that isn't quite true, and there radiating more RF then you can believe  can't be legal either.  So clearly I haven't worked a lot of HF since.  The local elevator installers tried everything in the book to help, they installed  filters  tried to  do any shielding  i suggested  

I can't make to many complaints as my antennas  on the roof   are at the whim of the co op and am lucky to have gotten there approvals for so many antennas up there.

As I find various  devices PWM based  it's amazing how RF dirty they are,  yet not all of them are, clearly if the company builds them correctly""  , they can be fine.

Clearly the larger issues, with us being hammered by 3rd parties that want to take our frequencies, and manufactures that are polluting the bands with poor (rf) designs I blame the FCC that turns their back and enforces little in that regard.

On Aug 16, 2012, at 1:30 AM, Roger (K8RI) wrote:

> The issue has dealt with specific makes and models with and without RFI, 
> but as PWM is by its nature an RFI generator we need to stop and think 
> About how companies (any company) acquires the motors and speed controllers.
> It's already been mentioned that one company was using PWM speed control 
> On a motor that ran at a constant speed.
> Do each of these companies use the same controller on the same model?
> Do they build the controller, or do they contract out the motor and 
> controller, or do they, like many stores contract out parts on a 
> periodic basis so that this year company A builds the controller for 
> company B's motors while next year company C builds the controllers. IE 
> can you, or can you not depend on the same motor and controller 
> combination for a specific model furnace/air conditioner?
> Perhaps when purchasing a system we should contract it out and stipulate 
> that the system generate no RFI.  I've had companies that would do it 
> for a complete GEO Thermal installation and some that refused. IE you 
> install it and if it works as the contract stipulates I'll pay you, 
> otherwise fix it or take it out.  Turns out our old system is so 
> efficient that it'd take nearly 50 years (47 point something) to reach 
> the payback at current rates. With the average system life of 25 years 
> or less ... we kept the old system.  OTOH with the extreme spring and 
> summer temps we've had this year it would have been quite a bit less, 
> but still not enough.
> You might have to pay a bit more, but as long as the final price is 
> within reason it would be worth it and there would be no haggling about 
> whether their system created RFI or not.
> 73
> Roger (K8RI)
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