How to make H-777 with RT21 RT-5R compatible?

The necessary condition for Retevis H-777, RT21 and RT-5R compatible is same frequency and same CTCSS. H-777:400-470MHz UHF analog radio RT21:400-480MHz FRS analog walkie talkies RT-5R:136-174/400-520MHz dual band keypad programmable hand-held transceiver Therefore, there is a common frequency range between the three of them. By programming them, they will be changed to same frequency and […]