Here's my experience with expanding the TRC-459.
You can't just run long wires from the original crystal's holes in the main pc board to a convenient switch you can reach from the outside of the cabinet. The wire length will throw the radio off frequency. The error will be so much that the trimmers you use to set channel center on the clarifier won't travel far enough to compensate.
The added wires will also make the radio even more unstable than it was on the stock 40 channels. It does tend to drift. Any mods to the oscillator circuit make the drift worse. Especially any mod that serves to increase the clarifier's range
When you finally go to the trouble of using diodes or a relay to switch the new and old crystal you will find that the new crystal is hard to get centered on the clarifier, even if you provide a separate trimmer cap for the new crystal. The original crystal is not correlated to the marked frequency with the standard "32 pf" compensation. If you order a custom-made crystal using that spec, it won't want to line up with the radio's original crystal.
Even if you get one mode lined up on the clarifier, the other two modes will be offset to one side or the other from that one.
The only cure I can see is something like the Galaxy Viagra kit. Not only does it have the added crystal for a new band, but a separate trimmer coil for each of the radio's 3 modes, one set of 3 for each new band.
And fitting a hand-built perfboard with all that stuff on it into this radio and getting it mounted close enough to the crystal's location on the main pc board is a whole 'nother challenge. Good luck with getting it crammed in there.
The true cost of modding this radio for upper channels will pay for a used radio that came with 6 bands.
Another one of those "Yeah you could, but why?" kinds of a mod.
73
