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measuring RF energy spectrum

measuring RF energy spectrum

measuring RF energy spectrum

(OP)
I'd like to measure the spectrum of the RF energy a motor is putting out.  Putting an antenna on a spectrum analyzer seems easy but how would I account for the antenna gain at its resonant frequency?  Maybe I need to do the measurements with several antennas of considerably different lengths?  How do laboratories examining RF noise handle it?

RE: measuring RF energy spectrum

Check
MIL-STD-461E
20 AUGUST 1999
________________
SUPERSEDING
MIL-STD-461D
11 JANUARY 1993
MIL-STD-462D
11 JANUARY 1993
DEPARTMENT OF DEFENSE INTERFACE STANDARD
REQUIREMENTS FOR THE CONTROL OF ELECTROMAGNETIC INTERFERENCE
CHARACTERISTICS OF SUBSYSTEMS AND EQUIPMENT

RE: measuring RF energy spectrum

bobm2
Typically a lab has a number of different antennas each
one calibrated for a range of frequencies. Your largest
trouble will be isolating the motor EMI from other sources
of EMI. Labs will place the motor in a chamber that eliminates outside RF and has walls that do not reflect
the RF energy from the test device back to the measurment
antenna. This gives the approximation of the motor by itself in an open area without reflected waves. You can buy
these calibrated antennas from places selling EMC test
equipment. Be prepared for some sticker shock.
If your motor is not too large to move the best solution may be to take it to a testing lab and get the results.
Rodar

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