From the FAQ on the Futaba website.
http://www.futaba-rc.com/faq/service-faq.html
The FCC requirements for the width of the signal output by RC radio equipment on 72 and 75 MHz was narrowed effective 3/1/91. MOST radios made before 1991 did not meet these new standards. MOST radios that did not meet the new standards could be 'narrowed' by authorized service centers from 3/1/91 to 3/1/98, thus making them legal to use. Canadian standards were changed effective 6/1/02 to comply with the same narrowband standards as the US.
How do I know if my transmitter is legal?
The easiest way to answer this is through a series of questions. If you answer YES to any of questions 1 through 6, you do not need to continue. Your radio is legal to use in the U.S. You may use a printout of this FAQ to show your club officials to avoid any confusion or concerns.
1. Is your TX on 27MHz? If so, it is legal, no matter what model or brand. ALL TXs on 27MHz are exempt from this rule. Note: Please check the actual frequency on YOUR transmitter. (For example: 72.590 is on the 72MHz band.) Many models of transmitter are produced on multiple bands, so just looking in your instructions to see what band it was produced on will probably not answer this question.
2. Is your TX either FM (PPM) or PCM or both? If so, it is legal, no matter what Futaba model it is. ALL Futaba FM and PCM transmitters met the standard.
3. If your TX is AM, does it have a label listing it as "Narrow Band", "1991" or similar? If so, it is legal because it either was legal at time of production or was upgraded to make it legal.
4. If your TX is AM, and it was manufactured on an odd numbered channel? Then it is definitely narrow band and legal. (Simply changing a crystal does not make the radio safe, narrow band, or legal.)
5. If your TX is AM, and it was manufactured on a channel below 38? Then it is definitely narrow band and legal.
6. If your radio is AM and is in the list below, it was narrow band and legal at time of production and is legal to use:
* 2NBL
* 2NCS
* 2NBR
* 2V
* 2VR
* 2CR
* 2DR
* 2PB
* 2PBKA
* 2PC
* 2PCKA
* 2PD-AM
* 4NBL
7. Is your TX on any of these frequencies: 72.080, 72.160, 72.320, 72.400, 72.960 or 75.640? If so, it is a very old 80 kHz unit and is not legal and cannot be made legal.
8. Gold sticker: If your radio is AM and is not on the list in step 4 AND does not already have a gold sticker on it (see photo), we cannot narrow band it for you. Unfortunately, under FCC regulation, we are no longer able to narrow band these old transmitters or otherwise provide any parts, information or service for these radios as of 3/1/98.