PMR 446 radio. What’s it for? Apart from school kids, teachers, local shops and offices, crane drivers and building site workers, 446 is for anyone who wants to chat locally. It’s licence free, but there are restrictions such as a maximum of 0.5 Watts ERP. Also, a modified aerial or radio is prohibited.
The radios have a CTCSS, continuous tone controlled squelch system, facility which will block out all signals other than the ones you want to listen to. For example, a school with 10 radios might use a tone of 88.5kHz. This means that the radios will only hear other radios that are transmitting that tone. Anyone else who might be transmitting on the same channel will not be heard by the school’s radios. Although the school radios block out other transmissions, others on the same channel will be able to hear the school radios.
There are people who use illegal equipment which covers the 446 channels. Running high power, 100 Watts or more, with outside aerials will allow communication over many, many miles. But this totally defeats the object of the system. It’s for local communication, perhaps from shop to office or head teacher to staff. Some people seem to be using the Baofeng hand held radios which pump out 5 Watts. Again, this is illegal but they are far superior on receive when compared with the average priced dedicated 446 radios. I suppose it’s rather like the old CB days when people used so-called burners to increase the power. Where will it all end?
PMR446 can be quite interesting to listen to. There are 16 channels and there’s usually something going on somewhere. I heard a chap the other day asking for more A4 paper to be brought up to the office. A woman replied, ‘get it your bloody self!’.
Baojie BJ-218 radio.
Pictured below is the Baojie BJ-218 VHF UHF radio which many people use for PMR446. Capable of 25 Watts, it’s totally illegal so don’t even think about using it to transmit! Having said that, it’s great for 2 metres and 70cms.
Homebrew 6 element beam.
Below is a 6 element beam for 446mHz made by a friend of mine. This is for receiving only as, obviously, it’s illegal to use such as aerial for transmitting. Channel 8 seems to be known as the DX frequency and, when conditions are good, French stations come booming in! I’ve heard ships at sea chatting on the 446 channels. In fact, anyone and everyone seems to be on the air using a variety of radios.
My XYL installing the aerial in the loft. Job done, pointing west, and working really well! Doesn’t she look happy!
Below is my new Sirio CX-440 PMR Antenna. The aerial covers 440 to 455MHz and doesn’t need setting up. It’s only about 20 feet high but it works extremely well. I’ve used RG214 coax to cut losses to a minimum. You can see the size of the 214 coax in the lower photo. The clamp type PL259 plug was advertised as suitable for 214 coax but it’s too small. I had to bodge it! It’s well worth investing in decent coax, I’m now hearing a lot more with this new set up. The gutter looks filthy… I haven’t got time to clean it.
Here is the manufacturer’s spec on the aerial…
- Type = 3/4 Wave Coax J-Pole
- Impedance = 50 Ohms
- Unbalanced Radiation (H-Plane) = 360 degrees
- Omnidirectional Radiation (E-Plane) = Beamwidth at -3 dB = 60 degrees
- Polarization = Vertical
- Gain = 2 dBd – 4.15 dBi
- Bandwidth at SWR 2:1 = 33.5 MHz
- Max Power = 200 Watts
- Feed System / Position = Gamma Match / Base Connector = N – Female
- Wind Load / Resistance = 25 N at 150 Km/h / 180 Km/h
- Height = 625 mm
- Weight = approx 450 grams
- Mounting Mast = 35 – 42 mm