[RFI] Comments on RFI from Ductless Air Conditioning Units?

[Larry Benko]

Jeff,

I am a retired EE and worked for years designing communications 
equipment for AT&T, medical equipment, and the general aviation industry 
communications.  All the equipment needed to meet various emissions 
standards (FCC part 15 A & B, CISPR 16, 17, 22, DO-160 etc).  At 
frequencies below 30MHz RF emissions are based on conducted currents and 
not field strength measurements with FCC part 15B being slightly less 
than 10uA (QUASI peak detector in 9KHz bandwidth).  A compliant FCC part 
15B device will generally not be heard at distances more than 20-30' 
away.  Of course there are so many exceptions to any generalizations in 
this area but this is a good starting guideline.

I happen to have all the equipment necessary to measure these currents 
and I realize that most folk don't so you need an alternate plan.  First 
of all it is your money and you dictate the terms to a contractor and if 
they don't like it find another contractor. Contractors deal with many 
suppliers and they need to talk to the manufacturers as to which ones 
will stand behind their products as being RF clean.  "Green" electrical 
appliances do not need to emit RFI that is objectionable.  To appease a 
contractor get them to take you to a place where they installed the same 
product you are interested in and let you listen for interference.  In 
this case they need to swear to you that you will get the exact same 
product and it will be installed the same.  That may appease the contractor.

If we don't return noisy appliances (such as the Whirlpool Duet) and 
demand better we lose.  The FCC seems to have no interest going after 
the bad lighting devices which are supposed to meet FCC part 18 and may 
actually be 10,000 times (40dB)over the limit. See 
http://www.w0qe.com/RF_Interference/grow_light_electronic_ballasts.html 
as an example.  Devices such as direct drive motors in furnaces and 
washing machines are not subject to any requirements in the US but they 
are in Europe and many companies who primarily deal in Europe will 
design products that are more RF quiet.

73,
Larry, W0QE


On 5/12/2013 11:37 AM, Jeff Stevens wrote:
> Has anyone had success specifying a term such as 'RFI Free' when
> dealing with a contractor?  Whenever there is AC (or worse yet, square
> waves) there is going to be SOME level of RFI, no?  The question
> becomes what level is acceptable for a particular installation.  In my
> case, if it's VLF/ELF noise or HF noise below the noise floor on
> antennas some distance away, I don't really care.  I can't, however,
> provide a more specific acceptable level such as a particular maximum
> field strength.  Something like 'RFI Free' seems rather amorphous and
> if I were a contractor, I'd be reluctant to accept such a term.
> However, if my customer provided concrete criteria (such as a maximum
> field strength) I might actually be able to get some specs from the
> manufacturer and have some reasonable confidence that I can perform
> the install in such a way as to meet my customer's needs.
>
> Just curious if anyone has brought RFI issues up, in writing, with a
> contractor and how that worked out.
>
> -Jeff
> W7WWA
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