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Amplifier Research NM-21FFT Radio Noise Meter-EMI Pollution Detector

Amplifier Research NM-21FFT radio noise meter provides highly accurate measurements for broadcast band EMI pollution. The NM-21FFT operates at one fixed frequency, either 834 kHz in the Northwest or 1000 kHz in the Northeast. These particular frequencies were chosen because there is virtually no broadcasting activity at these bands, allowing for surveys to be performed at power generator and transmission installations. It is also available at a fixed frequency anywhere in the range of 600 kHz to 1500 kHz.

Due to the single frequency capability, the instrument is inherently high in sensitivity and simple to operate. The absence of broad frequency coverage eliminates all tuning and calibration requirements. It also enables the circuitry to be designed for high image rejection, high IF rejection, low spurious response and high overall accuracy. The NM-21FFT conforms to NEMA-107 and ASA C63.2 specifications for single frequency RFI instruments and is compatible with the NM-17/27A and NM-25T for all pulse repetition rates above 50 pulses per second. The instrument is hand portable, withstands rough field use and has low (5 watt) power consumption.

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Feature Specification

Designed for use by the Power Industry
Accurate measurements for broadcast EMI pollution
Single frequency capability
Rugged construction
Hand-held portable device

Frequency Range	Single frequency, crystal controlled. Standard frequencies available are 834 kHz and 1000 kHz. Other special single frequencies are available in the range of 600 to 1500 kHz.
RF Input Impedance	50 ohms standard, Input VSWR is less than 1.25
Bandwidth	The 6 dB bandwidth is 5 kHz ±10%. The 60 dB to 6 dB overall bandwidth ration is 3.5 max.
Detector Function	Quasi Peak detector only. Time constant of one millisecond charge and 600 millisecond discharge.
Sensitivity, CW	Conducted: 50 ohm impedance -0.10 Î¼V
Sensitivity, Broadband*	Conducted: 50 ohm impedance -0.07 Î¼V/kHz *Signal plus noise to noise ratio of one with Quasi Peak detector.
Output Meter	Two 5-inch scales are provided. 1 to 1000Î¼V scale in Logarithmic increments 0
	to 60 dB above 1Î¼V linear scale, divided into 60 equal increments
Measurement Range	60 dB (Output meter range) in the lowest step attenuator position. An additional 60 dB of attenuation is provided in 10 dB steps for a maximum voltage of 120 dB.
Measurement Accuracy	±2 dB
Oscillator Radiation	Less than 50 Pico watts
Shielding Effectiveness	80 dB min.
Image Rejection	Greater than 90 dB at standard frequencies
IF Rejection	Greater than 90 dB at standard frequencies
Other Spurious Responses	Greater than 90 dB at standard frequencies
Loud Speaker	A small loud speaker with front panel level control is provided
Recorder Output	1.5 VDC across a 1500 ohm resistive load at full scale meter deflection. Recorder output is proportional to meter deflection.
IF Amplifier	Operates at 455 kHz
Size	152.44 H x 279.4 W x 304.8 D mm (6 H x 11 W x 12 D in)
Weight	Approx. 5.4 kg (12 lbs)
Power Supply	AC Power supply standard
AC Line Voltage	105/125 Volt, 50 to 70 Hz
Power Consumption	5 Watts