data over PMR radio uk

hippy

Technical Support
Staff member
It used to be "Speech Only, No Data" and I'm sure it still is, but since the Radio Authority got assimilated by Ofcom I've found it harder and harder to find definitive documents which don't refer to some other, and round and round it goes.

Start digging from here ...

http://www.ofcom.org.uk/radiocomms
 

xstamp

Senior Member
If you mean legal limits, these can probably be found by downloading a copy of ‘UK Radio Interference Requirements, 2030 Short Range Devices’ from the Ofcom website.

 

hippy

Technical Support
Staff member
Found it ... OfW57 is the old RA 357 ...

http://www.ofcom.org.uk/radiocomms/ifi/licensing/classes/business_radio/information/ofw57/ofw57.pdf

"Please note that it is for speech transmissions only" - So you would not be licensed to send data over PMR446 in the UK. There are however at least two grey areas ...

1) What is Data ? Any stream of data can be represented by a sequence of spoken words (speech) which would be licensed for transmission. This is I believe one way in which CB has been used for data transmission in Australia.

2) "You may also use speech privacy measures, including speech inversion, with PMR
446 radios" - What happens when that speech privacy measure is achieved in a way ( overlaying FSK/DTMF tones for example )where data could be transmitted and extracted as well as the original speech ?

I'm not going to advocate either.
 

Dippy

Moderator
Mmmm... sounds like you are wrestling with semantics there :).

I would have thought that modulating digitally would have introduced high harmonics which may be undesirable - I haven't looked at the band separation.

But, as it says, "voice only".
 

hippy

Technical Support
Staff member
And arguing semantics with a body which can take people to a Court which can impose fines and other penalties.
 

BeanieBots

Moderator
It was quite clear the last time I read up on it. "Voice only, not encoded" and that includes "no speaking in coded messages".
The reasoning is so that "someone" listening in can fully understand what is being said "without the need for any decoding device". So, you can't even have your own secret terminology.
Big Brother at its best!
 

Dippy

Moderator
This is the first (and probably last) time I've read it.
Suggest BB has another read - he sounds out of date. Hippy's (2) is a quote.

Anyway, to cut a very long story (and thread) short; stick to voice , then you won't get a knock on the front door.

Digitise at your peril...

PS. We at Thames House love listening to Beaniebot's phone calls.

Edited by - Dippy on 01/03/2007 16:00:04
 

BeanieBots

Moderator
Dippy, just for, I went and searched my library and found the document.
By my standards, it's up to date, 1976 !
(yes, that's right, POST war).

According to my copy, the rule about no encoding OR "secret language" is applicable to ANY voice only channel.

That was when the GPO was in charge, maybe things have changed a little since ;-)

P.S.
If you have been listening to my calls, then you'll know that I've also been listening to yours.
 

moxhamj

New Member
As an Australian, I presume this would be the British government worried about coded messages in speech. I suppose they are the experts at that, given the huge number of military campaigns co-ordinated through WW2 via coded speech on the radio. They wouldn't want anyone else getting in on the act.

So don't encode it! Use a free speech synthesizer on a PC to say things like "The temperature today is 25 degrees which in morse code/binary is beeep - bip - beeep etc. Use a picaxe to decode the morse bit, using a sound/no sound low pass filter/recitifer circuit. No secrets, nothing hidden. Only catch would be if you actually wanted to send a secret...
 
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