Features: 
1) Power readout directly in digital form without any calibration. 
2) Maximum measurable power range up to 20W. 
3) Check your Radio power output watt radio frequency under a second.
4) Easy connection with handheld Radio 

Specifications: 
Measurable power range: 0.1-20W 
Maximum power input: 20W
0-10W  (Measuring can not be continue for more than a minute )
10W-20W (Measuring can not be continue for more than a 30 second )
20W or more  (Measuring can not be continue for more than a 5 second  )

Caution :

RF power over 20W may damage the 50 Ω dummy load.

Metal body is heated while working.

Features function

Hold the red button for only 2 seconds then let go
Hold red button -" Power on " and "Frequency counter "mode
Push red button -" Power Meter "mode
Push red button -" Signal Level "mode
Push red button -" Battery Level "mode

1.1) How to use Frequency counter .
Two ways to use the frequency counter meter : 

A) Connect walkie-talkies with BNC

B) Receive radio signals from the top sma antenna

Hold red button --" Power on " and "Frequency counter "mode

Connect the antenna to sma .

20.000MHz to 999.999 MHz

1.2) How to use Power meter .
Hold red button -switch on
Push red button once to mode "POWER "
Connect the BNC to the radio output .

1.3) How to use signal input level .
Hold red button -switch on
Push red button twice to mode "receive "
Connect the antenna to sma.

1.4) How to check Battery level .
Hold red button -switch on
Push red button 3 times to mode "BAT "

Package Contents 

1x SF-20 POWER METER / FREQUENCY COUNTER
1x English User Manual
1x USB charger cable 
1x USB AC adapter 100-240V