PMR446 “UHF CB”

PMR446 is a license free radio service in the UHF portion of the radio spectrum, almost all radios for this band are battery powered handheld radios, though there are two notable exceptions which although still portable can be used as base stations.

PMR446 is divided into 16 channels, though older radios tend to make use of the first 8 as per the previous version of the standard. The radios have a fixed antenna (though in some cases they are just glued on and can be unscrewed), and a transmit power of 500mW.

Some radios for this band are cheap to buy and run off a set of rechargeable batteries, usually AAA or AA sized batteries.

Radios

The radios for this band are divided into two categories

  • Handheld – the most common and widely used type of radio on PMR446, they are available almost anywhere and can be obtained cheaply
  • Portable base – these run off batteries and the mains, the first attempt was the XT1000, then the cosmetically similar Intek DRS-5070 (of which a handheld version, the MT-5050 also exists), and then there is the Midland Base Camp446, which is designed to be able to be charged from an internal hand cranked generator, it is supplied with a hand microphone, an ideal option if you wish to use these as a base station.

No matter what type of radio you buy, they all have a fixed antenna, and transmit at 500mW within 8 or 16 channels, though some radios cover the LPD433 channels which is 10mW, it should also be noted however that LPD433 frequencies are shared with other higher powered licenced users, so you may receive interference from them

Accessories

There are a few accessories for PMR446 radios, these are as follows

  • Speaker microphones – if you use your PMR446 as a base station, you can use one of these with the radio, these may have one or two pins depending on radio they are designed to fit.
  • Headset – this is for use when out and about, again with the one or two pins to connect to the radio, the microphone is usually in-line on the cable with a PTT button there
  • Motorcycle helmet headset – these are designed for use on motorcycles, and are designed in such a way so as to include a PTT switch in a convenient place so as not to take your hands of the handlebars, although the radio may also be operated with VOX turned on but this can lead to the issue of not stopping transmission after you have spoken
  • Drop-in charger – this is to quickly charge your radio, usually these are supplied with the radio but more expensive radios such as the Intek MT-5050 are usually supplied with a charger that directly connects to it that slowly charges the batteries. A drop-in charger allows for quick charging of the batteries and no cables to unplug

Most specialist radio dealers will also supply replacement belt clips for some radios, replacement batteries for radios that require battery packs as opposed to regular batteries, and even antenna socket kits plus suitable antennas, though it should be noted that you need to know how to solder before installing such a thing and also ensure that the radio will still transmit within acceptable levels to keep it compliant

Unofficial UHF CB on PMR446

For information only, you do anything outlined below at your own risk, I take no responsibility for use of none-standard equipment on PMR446 or use of channels other than the 16 legal channels

The unofficial UHF CB service is PMR446 at higher power, some older standard PMR446 radios can be expaned to cover the 16 channels, the Intek MT-5050 and DRS-5070 are two of the more popular radios for this, both of which are opened by cutting 3 jumpers in the battery compartments, this also gives you 4 watts transmit power and a scrambler feature.

70cm Amateur radios are often converted for use on these channels, and some other UHF radios are often reprogrammed as well. Add to that that there are many cheap UHF handhelds available from China via the likes of eBay, particular the Baofeng BF-888 as it is extremely cheap, that can be programmed to use on PMR446, often with up to 4 watts transmission power and replaceable antennas. Some people convert PMR446 equipment to accept external antennas by fitting a BNC or SMA socket to them. This allows the use of high-gain antennas. Any antenna designed for the 70cm band is suitable to use on PMR446 as these channels form part of the bandplan of the 70cm band in the USA and Canada.  If using an external antenna do use low loss coaxial cable, do not use RG58 as it is very lossy at UHF frequencies and avoid, where possible, using PL259s as these don’t tend to work well at UHF frequencies.

This band isn’t affected in the same way as the 11m CB band down on 27MHz is by the solar cycle and thus is not as noisy, if your antenna is mounted above everything else you should be able to get a good range and local contacts will also be easier to obtain. Though if you want to do this legally I advise getting an Amateur radio licence and using the 70cm simplex channels instead though it requires you give a callsign at appropriate intervals, it is straight forward and easy to obtain a foundation licence.