Simple Frequency checking machine

This machine can detect the frequency of wireless remote control. The user only need to hold the little size machine near the remote controller less than 10cm, then its frequency will be desplayed on the screen.

Frequency rage: 250-450MHZ.
Operating voltage: DC7.5V-10V
Static current: 40mA
Operating current: 52mA
Detecting rage: less than 10cm between the machine and the remote controller