[GreenKeys] SITOR / AMTOR / NAVTEXT protocols

[Sam Hallas]

tony j. podrasky wrote:
> SITOR / AMTOR / NAVTEXT is different: there are different
> modes: you've got FEC, ALIST, etc.
>
> Does anyone know where I can find out what the protocols are?
As noted in some of the replies AMTOR is an error correcting protocol 
and normally works point to point, though it does have a broadcast FEC 
mode. It was originally deveoped by Peter Martinez (G3PLX?) and his 
article appeared in the RSGB magazine, RadCom, sometime in the 1980s. 
There are a number of programs available to decode it - search on Google.
Cheers, Sam
Here's what Wikipedia has to say:

AMTOR is a specialised form of RTTY protocol. The term is an acronym for 
AMateur Teleprinting Over Radio and is derived from the commercial SITOR 
system (Simplex Telex Over radio) developed primarily for maritime use 
in the 1970s. AMTOR was developed around the SITOR protocol in the early 
1980s and is used by amateur radio operators today

AMTOR improves on RTTY by incorporating error detection or error 
correction techniques. The protocol remains relatively uncomplicated and 
AMTOR performs well even in poor and noisy HF conditions. AMTOR operates 
in one of two modes: an error detection mode and an automatic repeat 
request (ARQ) mode.

The AMTOR protocol utilizes a 7-bit code for each character, with each 
code-word having four mark and three space bits. If the received code 
does not match a four-to-three (4:3) ratio, the receiver assumes an 
error has occurred. In error detection mode, the code word will be 
dropped; in error correction mode, the receiver requests that the 
original data be reset. AMTOR also supports FEC in which simple 
bit-errors can be corrected.

While still in use today, alternative protocols such as PSK31 are 
becoming favored by amateur operators for real-time text communications. 
AMTOR is still used for broadcast bulletins.