Bird - The RF Experts

Multifunction Power Meters

Dual Sensor Display

The Model 4421A is a Multifunction Power Meter to be used in combination with Bird’s Precision Power Sensors to display RF power readings with up to 0.5% accuracy. This intuitive display unit clearly identifies the Forward and Reflected power measurements within the RF path. In addition, return loss readings can also shown to provide additional insight into the RF system being monitored.

The 4421A is the next generation replacement for the industry standard Model 4421. Building upon the original model’s high level of accuracy and its ease of use, the new 4421A enhances the meter’s functionality by utilizing a smaller/lighter design, and by providing the ability to have dual sensor inputs.

  • Compatible with the full line of Bird's 402x-, 702X- and 703x-series sensors.
  • Automatic sensor detection for seamless integration.
  • Large 9.7" full color LCD touchscreen display for easy readability.
  • Dual sensor option expands measurement capabilities.
  • Compact, lightweight and portable design enhances functionality.
  • Forward Power in W or dBm
  • Reflected Power in W or dBm
  • Return Loss in VSWR, RL, or Reflection Coefficient

Product Selection Guide
Model Number # of Sensors # of Sensor Channels Remote Computer Interfaces  
4421A-10-00-0 Single 402x Sensor 1


4421A-20-00-0 Dual 402x Sensors 2 None
4421A-10-11-0 Single 402x Sensor 1 RS-232, LAN
4421A-20-11-0 Dual 402x Sensors 2 RS-232, LAN 
4421A-12-11-1 Single 402x Sensor
*Dual 702x / 703x Sensors 
2 RS-232, LAN

* 702x/703x Sensors are currently supported for Average Power measurements. Pulse Power parameter measurements will be added with a free, in-field installable software update by the end of 2023.

product specifications:
Item No
Item Name
Multifunction Power Meter
Compatible Bird Power Sensors
4021, 4022, 4023, 4024, 4025, 4027 Series, 4028 Series, 702x Series, and 703x Series
Power Range
Sensor dependent
Frequency Range
Sensor dependent
Sensor Channels
Model dependent: 1 or 2
VSWR Display
1.0 to 199.9
Return Loss Display
0 to 40 dB
9.7 in TFT full color LCD with touch screen
AC Power
100-240 VAC, 50-60Hz, 30 W
Fuse Rating: 1A, IEC (5 x 20 mm), Time-Delay
Type: Internal, rechargeable
Life: Up to 7 hours
Changer: Built-in. Approximately 4 hours to fully recharge.
95% max (noncondensing)
4,600 m (max)
Operating: 0 to 40 °C

-10 to 50 °C, < 1 month
-10 to 35 °C, < 6 months
-10 to 25 °C, > 6 months

1 - Storage temperature limited by battery specification. Storage outside this range may degrade battery performance. For best performance, a full recharge is recommended every 6 months or if stored below 0 °C.
10.6 in x 9.7 in x 3.6 in
(269 mm x 246 mm x 91 mm)
Less than 5 lb
CE Compliant
Shock and Vibration: MIL-PRF-28800F Class 4
compatible devices:
RF Calibration Kit
4020 Series
Directional Power Sensors
4027A Series
Precision Directional Power Sensors
4027F Series
Filtered Precision Directional Power Sensors
4028 Series
High Power Precision Directional Power Sensors
Coiled Latch-N-Lok Interface Cable
Carrying Case - 4421A Series Wattmeter and Power Sensors