Technical information
new era black and red capsFRS radios are limited to 500 milliwatts according to FCC regulations. Channels 1 to 7 are shared with low-power interstitial channels of GMRS, the General Mobile Radio Service. A license is required for those channels if the power output is over FRS limits.
Unlike Citizens' Band (CB) radios, FRS radios frequently have provisions for using sub-audible tone squelch (CTCSS and DCS) codes, filtering out unwanted chatter from other users on the same frequency. Although these codes are sometimes called "privacy codes" or "private line codes" (PL codes), they offer no protection from eavesdropping and are only intended to help share busy channels. Tone codes also do nothing to prevent desired transmissions from being swamped by stronger signals having a different code.
FRS stations on channels 1 through 7 may communicate with GMRS stations on those shared channels; the GMRS stations may use up to 5 watts of power, while the FRS stations are restricted to 0.5 watts.
The use of duplex radio repeaters and interconnects to the telephone network are prohibited under FRS rules, unlike GMRS which allows repeaters, and unlike the Amateur Radio Service. FRS radios must use only permanently-attached antennas. This limitation intentionally restricts the range of communications, allowing greatest use of the available channels.
FRS manufacturers generally claim exaggerated range. The presence of large buildings, trees, etc., will reduce range. Under exceptional conditions, (such as hill-top to hill-top) communication is possible over 60 km (40 miles) or more, but that is rare. Normal conditions, with line-of-sight blocked by a few buildings or trees, mean FRS has an actual range of 0.5 to 1.5 km (1/3 to 1 mile).
FRS/GMRS hybrid radios in the United States
Motorola FV150 FRS and GMRS handheld radio
Hybrid FRS/GMRS consumer radios have been introduced that have 22 channels. Many of these radios have been certified for unlicensed operation (on the 14 FRS frequencies, channels 1-14) under FRS rules.
The FCC rules and statements regarding the use of hybrid radios on channels 1-7 stipulate the need for a GMRS license when operating under the rules that apply to the GMRS. Many hybrid radios have an ERP that is lower than 0.5 watts on channels 1-7, or can be set by the user to operate at low power on these channels. This allows hybrid radios to be used under the license-free FRS rules if the ERP is less than 0.5 watts and the unit is certified for FRS operation on these frequencies.
Owners of hybrid radios should be aware that in the United States of America it is illegal to operate on channels 15-22 without an FCC GMRS license. Most radio manufacturers do not make this sufficiently clear to customers. Consequently, this can cause unlawful interference to GMRS licensees. As GMRS licenses cost money to obtain, such interference is a source of frustration for duly-licensed operators.
Channels 8-14 are exclusively for FRS. Accordingly, GMRS operation is not allowed on these channels. Channels 15-22 are reserved exclusively for GMRS. As noted, FRS operation is not allowed on these channels.
List of FRS channels
Channel
Frequency (MHz)
Notes
1
462.5625
Shared with GMRS.
2
new era black and red caps462.5875
Shared with GMRS.
3
462.6125
Shared with GMRS.
4
462.6375
Shared with GMRS.
5
462.6625
Shared with GMRS.
6
462.6875
Shared with GMRS.
7
462.7125
Shared with GMRS.
8
467.5625
FRS use only
9
467.5875
FRS use only
10
467.6125
FRS use only
11
467.6375
FRS use only
12
467.6625
FRS use only
13
467.6875
FRS use only
14
467.7125
FRS use only
Some clubs have recommended FRS Channel 1 as a national emergency/calling channel, such as REACT International, Inc. and the National SOS Radio Network.
Channel 2 is typically used by geocaching groups when trying to connect with other geocachers.
Similar services in other regions
Personal UHF radio services similar to the American FRS exist in other countries, although since technical standards and frequency bands will differ, usually FCC-approved FRS equipment may not be used in other jurisdictions.
Taiwan
Some manufacturers in Taiwan have radios that carry both FRS and GMRS frequencies, using channels 1 to 99. Channels 1 to 14 are well-known, while channels 15 to 99 are less popular.
没有评论:
发表评论