25 April 2005

Whadja say Donald??

This post is in response to several emails we've received from listeners monitoring the live scanner feed (who are lucky enough to get an open port...), who have written in to inform us that from time to time, the feed's audio gets 'garbled' and is unintelligible. First, we appreciate your concern, and second, we also appreciate you writing to us for any reason about the feed, as responses are still few and far between.

Now, with regard to the audio "problem"....
(Seasoned scanner listeners can fade here if desired)
Folks, what you're hearing when the scanner feed's crisp, clear audio suddenly sounds like Donald Duck as a deep sea diver trying to talk under water at 200 fathoms (without a mask...), is what's known as 'DIGITAL ENCRYPTION'. This is a feature of the new radio system which allows the users to encode or scramble their conversations by either pushing a button on their radios or switching to an 'always encrypted' talkgroup. The radio units, being micro computers in addition to 2-way radios, break down the users voice into digital 1's and 0's even when not operating in scrambled mode. The 1's and 0's that represent the voice are transmitted from one end of the conversation to the other, and are then reassembled to form the audio that comes out of the speaker. (By the way, this is the primary reason your old 'analog' trunking scanner will not allow you to listen to the new system). When in encrypted mode, the "sender's" radio 'scrambles' the order of the 1's and 0's before transmitting them. It also adds additional information to the signal which further complicates the encryption code, and that helps the receiving radio at the far end to unscramble the signal (a sort of virtual key to unlock the code). Private conversations over the airwaves using digital encryption are not brand new, and also have an analog cousin ('speech inversion') that has been around and in use for quite a while. There are no scanners on the market that have the ability to unscramble this type of code, and there probably will never be, as this method is virtually impossible to 'break into' from outside the system.

That is probably the most simplified explanation of digital encryption that you will ever find, but for the purpose of answering this question posed by those needing something less than a 15 page NASA-like dissertation, it should suffice.

In order to satisfy the seasoned scannists mentioned above who I know are going to write in to "correct" some this....
Yes, there are times when a bad signal between the "sender's" radio & the radio tower will cause a very similar sounding 'scrambled' audio. Basically, the signal in this case IS being scrambled, but is due to unintended signal weakness/interference and not by the intentional encryption method just described. This phenomenon can be easily distinguished from actual encryption as it usually only affects bits and pieces of a single transmission, allowing some of the words to come through normally.

Anyone that would like to add their 2 cents worth, please do so by clicking the 'Comments' link below.

Hope that clears the mud some....