Bird - The RF Experts
3126A, 3127A and 31278A Single Carrier, Wattcher RF Monitors

3128A, Single Carrier, Wattcher® RF Monitor
The 3128A Wattcher RF Monitor/Alarm; when installed with a dual port Thruline Line Section and two elements, is designed for the protection and monitoring of radio frequency transmission systems. The line section is selected to be compatible with the RF coaxial line used in the transmission system.

The elements are selected by the user to cover the desired power levels and frequency ranges. Purpose and Function Abnormal loading conditions cause the transmitter to quickly shutdown, a user selectable audible alarm to sound, and an alarm LED to flash. Remote access is available for resetting audible and visual alarms. Fail-safe or non fail-safe modes are user selectable and the reflected power trip level is adjustable.

3126A, 3127A and 31278A Single Carrier, Wattcher RF Monitors
product specifications:
Item No
Item Name
Single Carrier, Wattcher® RF Monitor
Power Range
100 mW to 10 kW using Bird® Plug-in Elements
Frequency Range
450 kHz - 2.7 GHz
Insertion VSWR
with N connectors 1.05 max. to 1000 MHz, 1.1 max. to 2700 MHz
± 5% of full scale
Meter Scales
FWD and RFL 25, 50, 100 W
Meter Sensitivity
30 µA/1400 ohm
Front Panel Buzzer and Red LED
Response Time
Activate Forward
Front Panel Controls
Reset push-button, reflected power limit display button, adjust alarm level recessed screw
Rear Panel Features
FWD/RFL DC signal inputs (BNC), DC power/remote reset connector, DPDT interlock relay connector, fail-safe/nonfail-safe selector, alarm buzzer disable, AC line voltage selector, safety fuses and IEC 320 AC receptacle
Includes two 25 ft. DC cables
AC Power
115/230 VAC, 50/60 Hz @ 0.125A
DC Power
9 - 16 VDC @ 1A
Gray Powder Coat
19” x 5 7/32” x 3 3/4” (W x H x D)
483 x 133 x 95 mm
5 lbs. (2.28 kg)
Required Products
Line Section: 4522-002-5
QC connectors: Two
Calibration Cycle
Two from Tables 1, 2, 3, 3A, 4, or 6
compatible devices:
7/8" Line Section
Table 1 - Standard Elements
7/8" Line Section - Standard Elements
Table 2 - Low Power Elements
7/8" Line Section - Low Power Elements
Table 3 - High-Frequency Elements, Entire Table ±8% FS
7/8" Line Section - High-Frequency Elements, Entire Table ±8% FS
Table 4 - Low Frequency Elements
7/8" Line Section - Low Frequency Elements
Table 6 - Milliwatt Elements
7/8" Line Section - Milliwatt Elements