PMR/8 Channel Radios

Rew

Theres alot of differnat radios knocking around but the most common type your likely to see is a PMR446. These are the ones that Lidle, Aldi. Agros etc sell.

PMR stands for Personal Mobile Radio. Its standard laid down in European law for licence free/exempt 2 way radios. The idea is that any one can buy them but you have to except that anyone else might be using the same channel as you, unlike licenced radio where its your own bit of the spectrum to use.

The work on a specfic set of fequencies within UHF 446MHz band:

Channel Frequency (MHz) 
1 446.00625 
2 446.01875 
3 446.03125 
4 446.04375 
5 446.05625 
6 446.06875 
7 446.08125 
8 446.09375

Another key feature of PMR446 is that the output power is limited to 500mw/0.5w. Anyone can make and sell a radio as long as it adheres to these frequencies and output power. That means that you get everything from cheap €20 radios up to €300+ ones. You will see some radios are advertised as having 304 channels. This is a marketing white lie. They still have 8 channels but a CTCSS (Continuous Tone-Coded Squelch System ) tone is used to make virtual sub channels. Each real channel is devided in to 8 sub channels. The CTCSS is a sub-audible tone (ie you cannt hear it) that acts like a key to unlock/open the channel only when that tone is part of the transmission.

CTCSS	Frequency
1	67
2	71.9
3	74.4
4	77
5	79.7
6	82.5
7	85.4
8	88.5
9	91.5
10	94.8
11	97.4
12	100
13	103.5
14	107.2
15	110.9
16	114.8
17	118.8
18	123
19	127.3
20	131.8
21	136.5
22	141.3
23	146.2
24	151.4
25	156.7
26	162.2
27	167.9
28	173.8
29	179.9
30	186.2
31	192.8
32	203.5
33	210.7
34	218.1
35	225.7
36	233.6
37	241.8
38	250.3

Does the price really make a diferance?

Yes and no

You can get bargin radios and pure ****e at the cheap end of the market like anything else. The quality/sensitivity of the reciver makes a huge difference to the how weak a signal you can hear. The over all build quality comes in to play with how robust the unit will be to knocks and the quailty of the components like speaker and mike will make an obvious differnace as well. TBH its very hard to tell at the cheaper end of the market how good or bad they may be. Hopefully some reviews and experiences posted up here will help with that.

Extended featues I have seen in more expensive radios are things like a voice scrambler/inverter, vibration, alert tones (plays a tone on the channel when a button is pressed), VOX, backlight, stop watch, and other misc stuff.

Any PMR radio will talk to any other PMR radio. The standard in the US is differnt so those radios won't talk to our ones and the frequencies they use would be illeagle without a licence here.

Headsets. Alot of radios now come with ear-bud headsets like older mobile phone handsfree headsets. They often have a PTT (push to talk) button on the headset so you dont have to go to your radio to talk. Depending on the pin setup of the radio it may be easy or impossible to buy other headsets for them. Big brands like Motorola are ok but even with Motorola there is single pin and dual pin depending on the model you buy. There are a few differant types of headset.

1) Earbud. as described above
2) Throat Mike. uses the vibrations of your thraot to pick up the sound, noramlly has a clear tube going up to the ear to hear but I have seen ear bud style ones
3) Boom mikes. They have an ear piece with a long bar coming out to the mouth with the mike on the end.
4) Remote Mike/Speaker. A square plastic box with a spearker and a mike, handy way to keep your radio protected but not very subtle as everyone around you will hear the speaker go off.

VOX. VOX is a sstem that activates the radios's transmit when you speak without you having to press a button. Sounds great but in practice it can be very troublesome as anything from noise around you to the wind could set off the channel.

Hope this helps I'm open to corrections/addtions.

Usefull Links:
http://en.wikipedia.org/wiki/PMR446
http://en.wikipedia.org/wiki/CTCSS