Asking for help,gp2000s sp66 p020 expand frequency

[bg4lma]

I am from China's ham, bg4lma, 30 years ago I learned a little English, poor, but I believe you can understand what I mean.

I have a Motorola gp2000s, also known as sp66 or p020, model: azh49ndk8aa9, 216-223Mhz, and I want to extend its frequency range.

Programming software can only enter numbers between 216 and 223. I downloaded a small program called "gp2000be.exe" on the Internet. It changed the UHF band GP2000S from 435-480 Mhz to 425-480 Mhz through the com port.

I connected the programming cable, ran the small software, and pressed "expand" to prompt for errors. I opened the EXE file with "hex-workshop" ,I want to find the keyword "425" and changed it to "210", but I couldn't find it.

Unable to do so, I used "hex-workshop" to modify the save files of the programming software, and changed a channel to 223.125 Mhz for both RX and TX. Fortunately, the programming software accepted it, without checksum, and successfully wrote it to the radio. After testing, the receiver is good, but press the TX button radio will emit a "beep" sound, not transmitting. The frequency is out a little bit of range and should be able to work. I would like to ask you to help me expand the frequency range of this radio, for example, is it necessary to short or add a diode or resistor near the CPU?

Good wishes to you.

[bg4lma]

After several nights of calculation, the problem has been solved successfully.

Because of the limitations of the forum rules, I can only explain a few key points simply, depending on your own understanding. Hope to help everyone.

1:(838.86075-freq）*20000=hexadecimal, the results must be arranged in reverse order, for example 12 34 56, in fact 56 34 12.

2:freq(MHz)*2.and then add four "0"=hexadecimal,the order is the same as above.

3:1 no need check, 2 need checksum16.