Although the frequencies of Channels 1 to 40 remain the same, the breadth of the frequency peak is narrower on the 80 Channel set. They refer to it as "narrow band". This allows them to squeeze the extra channels in between (ie Ch 41 sits between Ch 1 & 2 etc). Newer 40 Channel sets should be OK but older ones may be a bit too "broad" and interfere with the adjacent new channel. That's why they want to phase out 40 Channel sets. I doubt you can convert 40 to 80, although just before the introduction of 80 Ch they were selling the new sets with Ch 41-80 de-activated. After Day One of 80 Channels you could enter a code to open up the extra channels.