[aprssig] Error checking within APRS packets

[Guido Trentalancia]

On 20/06/2011 21:56, Guido Trentalancia wrote:
> Example (CRC-16-CCITT calculated with initial value 0xFFFF is appended 
> at the end after the pipe "|"):
>
> this is a normal packet which ends here|0x7886
>                  THIS IS A LOUD INTERFERER PACKET WHICH BEGINS A BIT 
> LATER THAN THE "NORMAL" PACKET AND WHICH IS SO LOUD THAT YOU CANNOT 
> FINISH READING THE "NORMAL" PACKET|0x520A
>
> time flows from left to right. What the receiver would decode is: 
> "this is a nTHIS IS A LOUD INTERFERER PACKET WHICH BEGINS A BIT LATER 
> THAN THE "NORMAL" PACKET AND WHICH IS SO LOUD THAT YOU CANNOT FINISH 
> READING THE "NORMAL" PACKET|0x520A".

Apparently, the alignment produced by my email client while composing 
the message is not the same as when the same message is read from the 
list...

So the second packet in the example might not be aligned (to the left) 
exactly as intended. When I read my own message now through the list, 
the loud packet begins at the "p" of the word "packet" in the first one.

Sorry about that, I hope it won't change much to the meaning (just 
suppose that the loud packet in the example above begins at the "o" in 
the word "normal")...

73,

Guido IZ6RDB