Tetra: Secure Digital Radio

Spannerman14

When is Tetra being rolled out? Who will be using it?

watty

Now.
The services (Garda, Fire, Ambulance), in theory. But they are not obliged to.

BravoMike

If you scan between 390 and 395 Mhz you may hear a buzzing sound (No Voice). This is range where the Tetra base stations operate. If you hear continuous buzzing you will know if tetra is active or at least being tested in your area.

deaglan169

ive noticed most of the garda stations up around me in monaghan have been kitted out already but they are still using analouge for the moment, the new antennas appear to be white not like the old green sigma antennas and are a continous diameter not tapered and usually have sever cable ties on the support arm to stop birds roosting there

Dankoozy

can you set up a tetra network for personal use?

hows direct-mode on those things, whats the range like?

watty

You need a licence from Comreg and a lot of money.

Direct mode would be someway between a CB and a PMR446. Not great. Only for people at same incident out of touch of base repeater.

Dankoozy

watty wrote: »

You need a licence from Comreg and a lot of money.

Direct mode would be someway between a CB and a PMR446. Not great. Only for people at same incident out of touch of base repeater.

how dare they keep such an awsome technology out of reach for ordinary people. the handsets are nice and solid too.


is there any decent digital 2-way radio for ordinary folk?

watty

Only with licence.

SSB still performs better for range and poor signal than Digital Voice. Digital Data can perform better, though for really poor signal or long range the speed is very low. SSB isn't easy to encrypt as it's analogue.

Shannon's limit.

Tetra is pretty rubbish and obsolete really. I'd not want a pair.

Digital Radio Mondail like digital system would perform better and is the only commercial Digital radio system with better than SSB performance. It could easily be encrypted to meet the needs of Tetra and supports faster data. Tetra data mode is worse than GSM GPRS never mind EDGE. I think the data mode must be related to original GSM (which is 14.4k, GPRS is up to 70k and EGDE 240k, EDGE2 1200k).

Dankoozy

ah sure as long as it supports the 2.4 kibbles required for AMBE or Speex

how is AMBE as a codec, besides the proprietaryness of it all how is it for quality

deaglan169

Dankoozy wrote: »

how dare they keep such an awsome technology out of reach for ordinary people. the handsets are nice and solid too.


is there any decent digital 2-way radio for ordinary folk?

there is some digital pmr446 radios you can buy similar idea to tetra but not so secure only need another person with one then they can listen in on you, but for experiementing with digital im sure they would give you and insight into digital think icom are doing them

Dankoozy

deaglan169 wrote: »

there is some digital pmr446 radios you can buy similar idea to tetra but not so secure only need another person with one then they can listen in on you, but for experiementing with digital im sure they would give you and insight into digital think icom are doing them

digital pmr yea, fairly limited and watty said the range was crap. is there anything better? but digital. dont care about encryption.

i dont believe there is a crypto the gubberment cant break so encryption seems fairly pointless to me. only one-time pads have half a chance

watty

There is Dstar for Amateur use. But it is poorer quality/range than FM in reality. SSB for same power beats FM x5 for range. (Licence needed) uses proprietary AMBE

Why you want digital? There is a huge advantage for Video, but none for voice unless you are using OFDM with iLBC or AAC
http://en.wikipedia.org/wiki/High-Efficiency_Advanced_Audio_Coding for Digital Radio Mondial
http://en.wikipedia.org/wiki/Digital_Radio_Mondiale
Useful bit rates with DRM range from 6.1 kbit/s (Mode D) to 34.8 kbit/s (Mode A) for a 10 kHz bandwidth (+/- 5 KHz). It is possible to achieve bit rates up to 72 kbit/s (Mode A) by using a standard 20 kHz (+/-10kHz) wide channel[4]


http://en.wikipedia.org/wiki/ILBC
At 13.33 kbit/s iLBC is superior to GSM, speex codecs and similar to G.729 (which need higher overall bit rate). iLBC unlike G.729 copes with packet loss. Unlike AMBE and G.729 it's free.

http://en.wikipedia.org/wiki/D-STAR uses obsolete codec tech,.AMBE which including overheads is 4.8kbps. But it sounds rubbish and needs better SNR than FM to work.

D-Star is a way to sell Icom Radios.

The future for personal two Way Digital Radios is some form of OFDM with iLBC or HE AAC. There is a open source two way version of Digital Radio Mondiale which uses only 4.5KHz bandwidth.

You can't break a one time pad at all. Ever.