MURS

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Multi Use Radio Service


MURS, American VHF CB, also rendered as "Multi-Use Radio Service" - not to be confused with similar services such as FRS/GMRS, regular old 26-27 MHz CB, VHF marine or licensed land mobile (business radio) services.

Short distance voice and data service for use by the general public for personal and business communications. Included in Part 95 of the FCC rules (Personal Radio Services) along with the more familiar services such as CB, FRS, GMRS, etc. Since it is a VHF CB service, MURS fills the gap between the UHF FM services (FRS/GMRS) and the original "Class D" HF AM/SSB 26-27 MHz CB service.

MURS is similar in function and intended use to the Freenet 149 MHz VHF CB service available in Germany and the "VHF 245" 245 MHz VHF CB service in Thailand, among other similar CB-like services worldwide. Many MURS users are business, commercial or industrial users.

Motorola RMM2050, a commonly used MURS handheld radio often found on construction sites, retail stores, and for similar purposes.


Contents

MURS Frequencies / Channels:

MURS Channel Identifier Frequency Maximum Bandwidth Remarks
MURS Channel 1 MURS-1 151.820 MHz 11.25 kHz Unofficial MURS calling channel
MURS Channel 2 MURS-2 151.880 MHz 11.25 kHz Recommended simplex repeater/crossband repeater channel
MURS Channel 3 MURS-3 151.940 MHz 11.25 kHz Recommended prepper/emergency management/disaster response calling/working channel
MURS Channel 4 MURS-4 Blue Dot 154.570 MHz 20.00 kHz Old Business Radio Service frequency, heavily used by stores, construction sites, etc.
MURS Channel 5 MURS-5 Green Dot 154.600 MHz 20.00 kHz Old Business Radio Service frequency, heavily used by stores, construction sites, etc.

MURS regulations, restrictions and other information

Maximum transmitter output power is 2 watts. No limit on effective radiated power (ERP). Antenna height is limited in FCC rules and the highest point of the MURS antenna must not be more than 18.3 meters (60 feet) above the ground or 6.10 meters (20 feet) above the highest point of the structure on which it is mounted.

Maximum bandwidth on 151.8200 MHz, 151.8800 MHz and 151.9400 MHz is 11.25 kHz and maximum bandwidth on 154.5700 MHz and 154.6000 MHz is 20 kHz. A3E and A2D emissions (AM voice and AM data) are limited to 8.0 kHz maximum bandwidth on all 5 MURS channels.

MURS is unique among the American (FCC Part 95) personal radio services (CB, FRS, GMRS, etc) in that AM, FM, CW, and data modes are allowed. F2D modulation and A2D modulation (digital using FM or digital using AM) are also permitted on the MURS frequencies. Voice inversion scrambling is permitted and offered as an option on radios such as the Motorola RMM2050 MURS portable radio. CTCSS and DCS are often used to facilitate frequency sharing. Because of the permissible data usage on the MURS frequencies, there are often data link networks heard on the MURS frequencies during VHF band openings.

Digital voice modulation (for example, DMR or MotoTRBO, Project 25 or APCO-25 P25, C4FM, D-STAR) or other digital voice modes may be used legally on the MURS frequencies - provided their emission bandwidth is less than or equal to the 11.25 kHz (for the 151 MHz frequencies) or the 20 kHz (for the 154 MHz frequencies) bandwidth restrictions. The 11.25 kHz narrowband is the same as the regular narrowband FM voice - known as NFM - required for frequencies above 150 MHz by the FCC since 2013.

Repeaters are not allowed on the MURS frequencies per FCC rules. This includes duplex and simplex repeaters, also known as "store-and-forward" repeaters. Store-and-forward packet operation is explicitly prohibited. Unattended data (or voice!) transmission (for example, telemetry) is permitted. MURS stations may not operate in continuous carrier mode (in other words, nonstop transmissions are not allowed). FCC rules specifically mention listen-before-transmit requirements for MURS systems, including datalink networks, to reduce the likelihood of interference. Even with modest outdoor antennas, MURS data link and telemetry systems can cover impressive range and cause annoying "squelch breaking" effects on FM voice radios on the MURS frequencies, especially in urban areas and rural areas with heavy farming or light industrial users where telemetry systems are common.

The 154 MHz frequencies were moved from the Business Radio Service (Part 90 of the FCC rules) and stations previously licensed to use these frequencies with higher power levels are considered grandfathered users and may legally transmit high power transmissions. Wal-Mart, Costco, Sam's Club and other retailers that started using 154.600 MHz and 154.570 MHz back when licenses were required have continued to use these frequencies after they were made license-free. Technically this means they're "grandfathered" users and enjoy primary status on the frequency - although this is murky in the FCC rules. Wal-Mart has a habit of using 154.57 and 154.6 with carrier squelch (CSQ), even in radio congested environments like large shopping malls and urban or suburban areas. This can lead to interference issues when multiple stores are using MURS frequencies in a small area.

CB networks on MURS, high power, militia groups, MURS repeaters, etc.

Some CB and ham radio operators also use the MURS frequencies due to favorable propagation characteristics, often with high power. This is against the FCC regulations but is widespread in certain areas due to the availability of open-band VHF/UHF radios, easily modified ham radio equipment that can transmit on the MURS frequencies and the adoption of the MURS frequencies by militia and prepper groups. MURS-based VHF systems range from simple handheld radios programmed with the MURS and FRS frequencies (for example, the Baofeng UV-5R and UV-82 series) to high powered mobile and base station simplex networks to simplex and duplex repeater networks.

There are reports of cross-band repeaters using the FRS frequencies and MURS, in addition to high powered MURS simplex repeaters located on mountaintops or tall buildings in urban areas. See also: CB repeaters.

MURS repeaters simplex repeaters cross-band MURS repeater listing

Reported MURS simplex repeater frequencies and tones include:

  • 151.8200 MHz MURS Channel 1 118.8 Hz CTCSS/PL - crossband with GMRS channel 22 462.725 118.8 Hz CTCSS/PL (New Jersey) (possibly off the air)
  • 151.8800 MHz MURS Channel 2 CSQ? - Monee, Illinois (grid square DM09) - unknown CTCSS/PL (possibly carrier squelch)
  • 151.8800 MHz MURS Channel 2 156.7 Hz CTCSS/PL - Mount Jackson, Virginia
  • 151.8800 MHz MURS Channel 2 156.7 Hz CTCSS/PL - Richmond, Virginia (low power, 2w transmitter, around 5w ERP - located in downtown Richmond, VA)


Please use MURS channel 2 if possible when setting up a MURS simplex repeater "parrot" or MURS cross band repeater.

It is recommended that MURS simplex repeater and cross-band repeater users use 156.7 Hz or 167.9 Hz as these CTCSS tones are used for interoperability and emergency purposes. MURS simplex repeater and MURS GMRS FRS crossband repeater operators should monitor frequency usage in their area, ideally for several weeks or more, to ensure they do not select a PL or DPL (CTCSS or DCS) tone that is used by another MURS user. Use of carrier squelch (CSQ) is strongly discouraged. If you decide to use MURS channel 4 (154.57 MHz) or MURS channel 5 (154.6 MHz) please verify that there are no Wal-Mart, Costco, Wawa or other similar stores in your area using those frequencies, as those stores use 154.570 and 154.600 MHz nationwide.


Emergency preparedness radio and communications guides, including the interoperability guide, recommend programming the MURS and FRS frequencies into radios for compatibility with these systems.

MURS Calling Frequency - Prepper/Militia Users - MURS Channel 3 151.9400 MHz

There is an effort (the AmRRON CH3 Project) to standardize the use of "channel 3" as a general "prepper" or emergency preparedness "calling" channel across the three Part 95 services, MURS, CB and FRS (MURS channel 3 - 151.94 MHz, CB channel 3 - 26.985 MHz and FRS channel 3 - 462.6125 MHz) in conjunction with HF/VHF/UHF amateur frequencies. MURS channels 1, 2 and 3 often have less activity on them compared to channel 4 and 5.

Emergency preparedness recommendations include monitoring channel 3 (CB, FRS and MURS) for 3 minutes at :00 (top of the hour), :15, :30 (bottom of the hour) and :45, so 3 minutes every 15 minutes - for emergency calls/communications. FRS users may also use channel 1 as the "default" channel or de facto calling channel, while higher power GMRS users officially use 462.675 [141.3 Hz CTCSS/PL]. See the FRS and GMRS pages for more information.

Militia and prepper users on MURS, MURS networks, simplex repeater discussion continued

Militia groups are encouraged to set up simplex repeaters on the MURS and FRS frequencies, ideally more than one (one for general use and another for "private" or "discrete" use). With CTCSS and DCS, there are literally hundreds of options and repeater access protection is possible even in urban areas with congested MURS and FRS/GMRS frequencies. You can use a different CTCSS or DCS (aka PL or DPL) tone for input and output, making the input tone "discrete" and only available to certain persons.

The cautionary statement above still applies. Prospective MURS repeater operators should monitor the channel they intend to use for an extended period of time. They should make note of any/all activity heard on the channel, with special attention paid towards the CTCSS/DCS (PL/DPL) tone squelch tones or codes in use. Even if a channel appears to be quiet with casual listening...that is often not the case. Some users only appear during specific times of the day/week. Make a list of all the CTCSS and/or DCS tones in use on your intended channel and exclude these from any simplex MURS repeater programming/channel plans you intend to use.

Data bursts on MURS, telemetry systems MURS datalinks

Because the FCC rules allow for any mode on the MURS frequencies (as long as the bandwidth restrictions are followed), MURS is becoming more and more popular for unlicensed fixed or point-to-point data link and telemetry systems. Someone scanning the MURS frequencies will often hear short data bursts (often just breaking the radio's squelch). Sometimes multiple systems can be heard on the same frequency during favorable band conditions and depending on the height of the receiving (and transmitting) antennas.

Short range on-site paging and one-way voice driveway sensors are also found on the MURS channels. Due to the favorable propagation characteristics of the 150 MHz VHF band, telemetry systems using MURS are sometimes used as an alternative to unlicensed 26 MHz/27 MHz telemetry systems. However, FCC rules permit higher power for telemetry, data links and telecommand purposes on the six 27 MHz R/C frequencies. The MURS rules specifically permit use of all 5 MURS channels for telemetry or telecommand.