December 2017 11
OPEN COMMUNICATION ; BY LOU FRENZEL W5LEF
Like all the other personal radio services, MURS is
approved and regulated by the Federal Communications
Commission (FCC). Its intended users are individuals
and businesses who need to have some type of wireless
communications service. It won’t replace your smartphone,
but it will provide a two-way communications capability for
some special situations.
You can read all the nitty gritty regulatory details in
the Code of Federal Regulations (CFR) 47, Part 95. You
can get that online from the FCC at www.fcc.gov. If you’re
going to use MURS, you should have a copy of this just to
familiarize yourself with the guidelines (see Part 95 Subpart
J, 95.1301 through 95.1317, and 95.632 through 95.639).
Some new guidelines are covered in the revised Part
95 from 95.2700 to 95.2799. It sounds complex and
legal, but it’s all very short and easy to read. Not bad for a
You can use MURS for voice or data applications. It
works like any other two-way voice radios such as those
used for CB, GMRS, or FRS. It’s a half-duplex service with
push-to-talk (PTT) convenience. You can also transmit serial
binary data to link computers, collect and send telemetry
data, or perform remote control.
Maximum output power for a MURS transmitter is two
watts. That’s not as much as GMRS permits, but lots more
than the 0.5 watt of FRS units. This translates to longer
range and greater reliability.
Frequency of Operation
MURS operation is permitted on five channels. The
channel designations and approved bandwidths are shown
in Table 1.
These radios will typically be frequency modulation for
voice or frequency shift keying (FSK) for data. You must use
narrow band frequency modulation (NBFM) on channels
1 through 3 with a deviation not to exceed 2. 5 kHz. You
can use a deviation up to 5 kHz on channels 4 and 5.
According to the regulations, you can also use AM or ASK,
or even Morse code communications if you know it.
With bandwidth and modulation restrictions, the data
rate is pretty low. For most industrial applications, the low
data rate is okay. Depending on the modulation, there is a
maximum data rate of about 5 kbps.
This depends so much on the environment between
n my April article on Personal Radio Technologies, I covered three types that
individuals can use. These are Citizens Band (CB), General Mobile Radio
Service (GMRS), and Family Radio Service (FRS). However, I forgot one. It
may even be a better choice for you than any of the others. It’s called MURS
which stands for Multi-Use Radio Service. Let’s take a look at the details here.
Services: The MURS Option
Another radio you can use license-free.
Channel Frequency (MHz) Max. Bandwidth (kHz)
1 151.82 11.25
2 151.88 11.25
3 151.94 11.25
4 154.57 20
5 154.60 20