Quite a few sellers are offering TETRA radios for sale on eBay and a few are promising SECURE DMO transmissions. I am a serving MOD police officer and while not an expert on TETRA radios I have a working knowledge of the system (Airwaves) and would hate to see someone spend upwards of £300 on a defunct system or one that won't give whats promised.
TETRA is basically a Push To Talk (PTT) mobile phone, using the mobile phone network (O2 in UK for Airwave), hence an authorization code is required to use the system.
Any second user radios offered on eBay will not be authorized to use the system, as the codes will have been removed before the radios were decommissioned, so no national coverage or data transmissions.
Any radios released with the codes intact can be remotely disabled if an unauthorized user attempts to access the system. Some high end radios have GPS tracking systems, so an unauthorized user may get a visit from the authorities!!!
This leaves you with a basic hand held "walkie talkie". Most TETRA radios have a Direct Mode Operation (DMO), this is a fallback mode if the network fails and offers short range use between units. Some newer radios retain their digital transmission capabilities most revert to analogue. The power output is in the range of 500mw to max 1w, similar to 446 pmr. The car/base units can have up to 10w.
Note: even if the unit keeps it's digital capability in DMO, there are digital scanners available to the public that are capable of intercepting the signals ( yes, very expensive but available non the less), also the Security Services use highly sophisticated systems ( I've seen them and believe me, I know what they can do), so without the encryption your transmissions are NOT completely secure.
Now on to the claims of "secure encrypted transmissions". The radio manufacturers and The End Users spend millions of pounds developing these systems, hence the encryption keys and algorithms (E2EE, ETSI, TEA1, TEA2 etc) are a closely guarded secret. Do you really believe a radio is going to be decommissioned with these keys intact?, I don't !!!!. You may be lucky and get a US radio with the basic End To End encryption intact, but ANY TETRA radio designed to be used in the UK and possibly Europe WILL (I repeat WILL) have the encryption disabled. This leaves you with a £300, 500mw, unencrypted walkie talkie on a non standard, illegal analogue (possibly digital) frequency, not a good buy!
People are still advertising radios as "totally secure", but all someone needs is the same type of radio, on the same frequencies and guess what?..... they will be able to hear you.... YOU WILL NOT GET ANY SECURE ENCRYPTION OPTION WITH ANY UNLICENSED, SECOND USER RADIO SOLD ON EBAY. You are buying digital handsets only, that CAN be monitored by ANYONE with the same type of equipment. The ONLY way you will get TOTALLY SECURE communication, is to be a licensed, authorised, fully paid up user of the networks. Two used handsets from Ebay, WILL NOT I repeat, WILL NOT be secure. If you don't believe me look at the manufactures websites, where they state that full encryption is the only option for secure comms. ALL encryption algorithms WILL have been REMOVED from all of the radios for sale on Ebay.
UPDATE: 02/10/08 Some IDIOT has just paid £3100 for a single Motorola handheld unit because the seller said it was popular with Government Agencies and it could be reprogramed to all their own needs, (hint, hint, you could listen to the police). If people are that gullible then they deserve all they get!!!
NO TETRA RADIO AVAILABLE ON EBAY IS ABLE TO AND NEVER WILL BE ABLE TO LISTEN TO POLICE TRANSMISSIONS REGARDLESS OF ANY CLAIMS MADE
Well that's my Two pennies worth. As I've stated I'm not an expert but I would hate to see buyers duped into buying a very expensive doorstop.