Hi Gramps98,

1) Yes, AM is still usable for aircraft, but the main drawback would be it's susceptibility to interference. The 4L is not legal for use if it has not been converted over to "narrow band". If you do not see an AMA gold sticker on the back of the transmitter, it is not narrow banded and thus illegal per the FCC for use.

2) To match up a flight pack, you would just need to make sure that the transmitter is legal for use today, and if it is, then most current flight packs will work as long as they match up to the transmitter in modulation and frequency. You may want to check our website at: http://www.futaba-rc.com/faq/product-faq.html, for some helpful information on older and current systems.

3) It is not legal to change the frequency of a transmitter, you can change the channel on a receiver as long as the change does not cross the Low or High band range. Either our service center or an authorized service center can change the channel on the transmitter for you and make sure that the transmitter is correctly tuned.

I hope you find this information helpful. You can also reach our Futaba support technical team at 217-398-8970, or via fax at 217-398-7721.

Sincerely,
Krysta
Lead Futaba Customer Service and Programming Technician
Also you may want to check our Website at (http://www.futaba-rc.com)