Most UHF radio licenses in the US are for the 450-470 MHz band. In the past the FCC divided this 20 MHz band into 800, 25 kHz-wide channels in order to allow each user to operate with his own licensed frequency. Federal frequency coordinators have allocated these 800 channels to users in various geographic regions around the country. As UHF usage increased, some regions ran out of channels. Accordingly, in 1995 the FCC announced a three-phase plan to double the number of channels to 1600 by licensing operation in narrower, 12.5 kHz channels. The three phases are:
Phase I: Restrictions on the certification of new radios
Phase II: Restrictions on new licenses
Phase III: Restrictions on all licenses
The FCC implemented
Phase I in 1997 when they began certifying radios only if they were capable of operating in 12.5 kHz or narrower channels, or with spectral efficiency equivalent to 4800 bps in a 6.25 kHz channel. This “spectral efficiency” clause means a radio can operate in a 25 kHz channel if it transmits at least 19200 bps. All Pacific Crest radios certified since 1997 have met this narrowbanding definition: they either operate in 12.5 kHz channels or they transmit 19200 bps in a 25 kHz channel. Some can do both.
On 1/1/11, the FCC implemented Phase II of the narrowbanding plan and started issuing new 25 kHz licenses only in rural areas or for special purposes. These licenses were rare. When 25 kHz licenses came up for renewal, they were almost always replaced with 12.5 kHz licenses. Pacific Crest believes it is prudent to assume that the FCC will not grant any 25 kHz licenses after 1/1/11. But if you do get a 25 kHz license, it will require you to transmit at least 19200 bits per second.
On 1/1/13, the FCC will implement Phase III of the narrowbanding license plan and require all users to transmit in 12.5 kHz channels at any speed or in 25 kHz channels at 19200 bps. Transmitting more slowly than 19200 bps in a 25 kHz channel will be illegal in the US. Furthermore, we expect that licenses for 25 kHz / 19200 bps operations will be very rare, if there are any at all. Unless you are a very special case, you should expect to be restricted to 12.5 kHz channels when any of the following occurs: you get a new license, your existing license is renewed or 2012 ends.
Here are answers to some common questions specific to Pacific Crest radios:
Q: I have a 25 kHz PDL radio. Is it 25 kHz only?
A: Yes. Only ADL-generation radios are user-configurable for operation at both 12.5 and 25 kHz. You can continue to use 25 kHz HPBs, LPBs, EDLs, RFMs, etc. until your license expires. However, you probably will not be able to renew your 25 kHz license and so will have to stop using your 25 kHz radio.
Q: I have a 25 kHz PDL radio. Can I legally use it after 1/1/13?
A: Only if you have a license after 1/1/13 for this mode of operation. These licenses will be hard to get and you will be restricted to a radio link rate of 19200 bps.
Q: How can I tell if my PDL radio transmits in 12.5 kHz or 25 kHz channels?
A: For LPBs, Sitecoms and EDLs, look at the model number on the side of the radio. If it ends in “12″ it’s a 12.5 kHz model. If it ends in “25″ it’s a 25 kHz model. For HPBs, look at the part number on the label. The following are 25 kHz HPB part numbers:
- A02531
- A02533
- A02535
- 56651-42-00
- 56651-44-00
- 56651-46-00
- 56651-44-10
- 56651-46-03
All other HPB part numbers are 12.5 kHz models. You can also connect your PDL radios to PDLCONF configuration software. The channel bandwidth is displayed on the Identification screen.
Q: All of my radios are receivers. How does any of this affect me?
A: It doesn’t directly affect you because the new regulations only restrict transmission. However, if you use a 25 kHz radio to receive data from a 12.5 kHz transmitter, you will pick up the desired signal but you also will receive signal from any radio within range that is transmitting on an adjacent 12.5 kHz channel. The mixing of the two signals will make both unintelligible. In practice, using a 25 kHz radio to receive a 12.5 kHz transmission doesn’t work well.
Q: Will I be able to continue using an ADL radio after 1/1/13 even though it is capable of transmitting in a 25 kHz channel?
A: Yes. Even if the FCC decides to forbid use of a radio that is physically capable of transmitting in a 25 kHz channel (not likely), Pacific Crest will release a version of firmware that will prevent such transmissions. The bottom line is that your ADL radio will remain legal even according to the most conservative interpretation of the FCC policy for 1/1/13.
Q: How fast can I operate in 12.5 kHz channels?
A: : This depends on the protocol and modulation type you select. The following table shows what link rates are supported by various combinations of protocol and modulation types:
| Protocol Type | Modulation Type | Radio Link Rates (bps) |
| Transparent FST | 4FSK | 9600 |
| Transparent EOT/EOC and Packet Switched | GMSK | 4800 |
| Transparent EOT/EOC and Packet Switched | 4FSK | 9600 |
| TRIMTALK 450s | GMSK | 4800, 8000 |
| TRIMMARK II/IIe | GMSK | 4800 |
| TT450S (HW) | GMSK | 4800 |
| TRIMMARK 3 | GMSK | 9600 (USA) |
Q: How does the narrowbanding policy affect my GPS receiver?
A: If your GPS receiver includes an internal UHF radio transmitter, the same FCC rules apply to it as to stand-alone transmitters: no more licenses after 1/1/11 and no more use (probably) after 1/1/13. To see what type of radio you have, use the receiver’s radio configuration software to connect to the radio. The channel bandwidth is usually displayed on an identification screen. If your GPS receiver’s internal radio only receives, there is no effect as the FCC’s narrowbanding policies affect only transmitters.
Q: My 25 kHz radio can transmit data at 19200 bps. This is the “equivalent efficiency” of 4800 bps in a 6.25 kHz channel, which satisfies the FCC’s narrowbanding requirement. So why do I need to switch to 12.5 kHz radios?
A: It is true that the FCC has defined narrowbanding as operating in 12.5 kHz or narrow channels OR transmitting at least 19200 bps in a 25 kHz channel. But that doesn’t mean they will automatically license any 25 kHz operation. In fact most observers believe they will NOT issue any more 25 kHz licenses except in special cases. The FCC has always been clear that their goal is to allow more licenses to be granted. The only way to do this in a limited frequency band is to require narrower channel bandwidths. Therefore, Pacific Crest believes it is prudent to switch to 12.5 kHz-compatible radios on or before the expiration of your 25 kHz license.
Q: Will there be a Phase IV – a requirement to use only 6.25 kHz channels?
A: Perhaps, but the FCC has issued no statements on this. Note that the FCC continued to license 25 kHz operation for 16 years after they announced the plan to migrate to 12.5 kHz. Will they issue only 6.25 kHz licenses beginning 16 years from today? Time will tell. You can be sure, however, that if this day ever comes, we’ll have a radio waiting.
Reproduced from Pacific Crest FCC Narrowband Requirements 022012.pdf document
Posted by Stakemill 
