Amplifier Research NM-21FFT Radio Noise Meter–EMI Pollution Detector
Description
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.
Features
- Designed for use by the Power Industry
- Accurate measurements for broadcast EMI pollution
- Single frequency capability
- Rugged construction
- Hand-held portable device
Specifications
|
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 μV |
|
Sensitivity, Broadband* |
Conducted: 50 ohm impedance –0.07 μV/kHz *Signal plus noise to noise ratio of one with Quasi Peak detector. |
|
Output Meter |
Two 5-inch scales are provided. 1 to 1000μV scale in Logarithmic increments 0 |
|
|
to 60 dB above 1μV 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 |
