• Frequency range 1.5 MHz to 2 GHz
• AM and FM measurement over full range
• Automatic tuning and level setting
• LED lock indication
• Weighted measurements
• Overload protection
• Compact and light weight

4561D is an Automatic AM-FM Modulation Meter designed for extensive use in accurate AM-FM measurements in development, production, testing, servicing and maintenance of static and mobile communication systems. This instrument provides high sensitivity of the order of 10mV upto 2 GHz with useful response upto 4 GHz. De-emphasis facility is also provided. Eleminating the need to manually tune a local oscillator and make level adjustments, this instrument speeds up measurement and improves accuracy. Being compact, light weight and portable it is an ideal instrument for field work.

Specifications

Frequency Range : 1.5 MHz to 2 GHz continuous coverage. Useful response upto 4 GHz.
Input Level : 10mV to 1Volt.
Overload : Upto 7 volts. (rms)
Input Impedance : 50 ohms (nominal)
Acquisition Time : 1 sec. (Typical)
Lock Indication
& Level Monitor : LED.
Display : 3 digit LED display

Audio Filters
Ranges : 25 Hz - 60 KHz
25 Hz - 15KHz
300 Hz - 3 KHz
Response : +0.5 dB with respect to 1 KHz
De-emphasis : Selectable 50µs. 75µs or 650µs

FM Measurements
FM Ranges : 10 KHz, 100KHz
FM Resolution : 0.01 KHz for 10 KHz range
0.1 KHz for 100 KHz range
Accuracy : +1% of FS +2% of reading at 1 KHz rate, plus deviation error of approximately +20 Hz at carrier frequencies upto 100 MHz and thereafter increasing at 6 dB per octave (over the temperature range 5°C to 45°C)
Residual FM : Less than 100 Hz at 500 MHz
Distortion : Less than 1% for 100 KHz deviation at 1 KHz rate.
AM Rejection : At least 80% in FM mode with 100 KHz deviation at 1KHz rate.
Measurement : - Peak Positive deviation
Modes - Peak Negative deviation
- Mean of positive and negative measurements.
- Difference between positive and negative measurements.
- Speech average to indicate relative loudness of audio.
- Selection of Psophometric filter (CCITT).

Signal Output
IF Output : 420 KHz, 100mV (Nominal) through
50 Ohms BNC Connector on rear panel.
AF Output : 0.5 V at FS, 600 Ohms BNC Connector on front panel for 10 and 100 AM/FM range.
Power Requirement : 230V AC + 10%. 5VA typical.
Dimensions : 112mm x 226mm x
(Approx.) 303mm (HxWxD)
Operating
Temperature : 0°C to 55°C
Humidity : 95% RH at 40°C
Weight (approx.) : 3Kg.
Accessories : N to BNC Adaptor, BNC-BNC cable,

AM Measurement
AM Ranges : 10%, 100%
AM Resolution : 0.01% for 10% FS range
0.1% for 100% FS range
Accuracy : +1% of FS, +2% of reading & residual AM (over the temperature range 5°C to 45°C)
Residual AM : Less than 0.5% with a 15 KHz bandwidth selected.
Distortion : Less than 1% for 80% at 1KHz
Measurement : - Peak
Modes - Trough
- Mean between peak & trough
- Difference betwen peak & trough
- Speech average to indicate relative loudness of audio
- Selection of Psophometric filter (CCITT)
Optional Features : - 200 KHz FM range
- Dual Battery operation