How to Extend Retevis RT85 Frequency Range?

Retevis RT85 Full Power Dual Band Ham/Amateur Radio, Dual Band, 200 Channels of Storage. But if you want to write frequencies other than 144-146MHZ and 430-435MHZ but cannot write the frequencies, you must perform spread spectrum. There are two methods, please do as follows:
The first is to turn off the walkie-talkie, press button 1 and button 7 at the same time, then turn it on
The second is to turn off the walkie-talkie, press the F key and the 1 key at the same time, and then turn it on again.


More details:https://www.youtube.com/watch?v=XUulc3oN-Oga