47 C.F.R. § 90.214
Transmitters designed to operate in the 150-174 MHz and 421-512 MHz frequency bands must maintain transient frequencies within the maximum frequency difference limits during the time intervals indicated:
| Time intervals1 2 | Maximum frequency difference3 | All equipment | |
| 150 to 174 MHz | 421 to 512 MHz | ||
| Transient Frequency Behavior for Equipment Designed to Operate on 25 kHz Channels | |||
| t14 | ±25.0 kHz | 5.0 ms | 10.0 ms |
| t2 | ±12.5 kHz | 20.0 ms | 25.0 ms |
| t34 | ±25.0 kHz | 5.0 ms | 10.0 ms |
| Transient Frequency Behavior for Equipment Designed to Operate on 12.5 kHz Channels | |||
| t14 | ±12.5 kHz | 5.0 ms | 10.0 ms |
| t2 | ±6.25 kHz | 20.0 ms | 25.0 ms |
| t34 | ±12.5 kHz | 5.0 ms | 10.0 ms |
| Transient Frequency Behavior for Equipment Designed to Operate on 6.25 kHz Channels | |||
| t14 | ±6.25 kHz | 5.0 ms | 10.0 ms |
| t2 | ±3.125 kHz | 20.0 ms | 25.0 ms |
| t34 | ±6.25 kHz | 5.0 ms | 10.0 ms |
1on is the instant when a 1 kHz test signal is completely suppressed, including any capture time due to phasing.
t1 is the time period immediately following ton.
t2 is the time period immediately following t1.
t3 is the time period from the instant when the transmitter is turned off until toff.
toff is the instant when the 1 kHz test signal starts to rise.
2 During the time from the end of t2 to the beginning of t3, the frequency difference must not exceed the limits specified in § 90.213 .
3 Difference between the actual transmitter frequency and the assigned transmitter frequency.
4 If the transmitter carrier output power rating is 6 watts or less, the frequency difference during this time period may exceed the maximum frequency difference for this time period.
47 C.F.R. §90.214