1qtrflash,
First off, welcome to RCU. I hope that we can help you get into the great hobby of RC. Now for your radio question. I'm more than likely going to be "rationalizing" that DX-7 for you. Any radio from the 80's is more than likely going to be illegal. Back in the early 90's the FCC mandated that all 72 Mhz radios be narrow banded, and this made most of the radios that were made in the 80's (and earlier) illegal. You can look on the bottom or back of the radio and see if there is a gold sticker on there that certifies that it's narrow band, but my advice would be to donate that radio to a museum and get a new radio. I'm about 99% certain that you can't legally use that radio. And if you do there is a good chance that you can knock others planes out of the air. Those old radios can take up 3-5 (or more) channels on our current day frequency chart. Get a new radio and don't worry about it.

Hope this helps

Ken