There are three methods for expansion, you can change the 19Mhz crystal for a permanent shift,or build my crystal switch to use both bands ( the plans are in the build it pages ), or you can change the programming on the PLL.

I am going to describe the programming method as the others are easy enough to do.

This will give another band of 40 channels 64 channels above the existing band

Cut the track that goes to pin 11 on the PLL and run a wire to each side of the cut, attach the other ends of the wires to a switch.

When the switch is closed the set is on the normal band, when the switch is open the set will be on the new band 64 channels above the old one.

This set is capable of having a greater amount of channels because of the PLL's abilities but you will loose the original band because the tuning won't stretch too far.