This one will be short as I don’t have a lot of time and there isn’t so so much to report. I have been able to identify the EPROM checksum routine and was able to trace where in the code the frequency entry code checks the entered frequency for correct range.

Thus, I was able to patch the bounds checking routine as well as the checksum to get this when entering 28 MHz:

Looks good as a first step!

Unfortunately, after several seconds I get this:

So there is a second bounds checking. Tomorrow I will try and trap on that message to find where that code is and do another patch.

At least I have verified that I found the data entry bounds checking code and know how to patch the checksum to not produce a BITE error.

So far, promising, and progress.