[CQ-Contest] New RBN Pattern File for fall contests

[Pete Smith N4ZR]

As many of you may be aware, the RBN uses CW Skimmer, and CW Skimmer 
uses what's called a pattern file to distinguish between legitimate 
callsigns and scraps of other CW communications.  The files identify 
patterns consisting of up to 3-character explicit prefixes and 1-3 
character numeric and alphabetic wildcards. Here's a tiny sample:

+ CE6@
   CE6@@
+ CE6@@@
   CE7#@@
   CE7@@
+ CE7@@@

So for example, CE6A (or any other CE6 plus one letter) is judged to be 
reasonably common, and Skimmer would only need to "hear" it twice before 
deciding to spot it. This doesn't mean in a single transmission - 
Skimmer "listens" to a 50-hz wide decoder, using a 256-character FIFO 
buffer, so as long as a station doesn't QSY more than that, it's treated 
as one transmission.  CE7AA does not have a "+", and would need to be 
heard three times.  CE7@ (that is, CE7A or any other single letter) does 
not appear on the list at all, and would have to be heard 4 times before 
it would be spotted.

My impression is that the rash of odd callsign prefixes of the last 10 
years or so has abated considerably, but it's always possible that there 
are still new calls out there that would require a revision to the 
pattern file.  For example, if a BY4AA (random example), were to acquire 
BY4A, they would go from being spotted after two repetitions to 
requiring four.

If this is your situation for the upcoming contest season, please e-mail 
me by September 25, and I will put out a new pattern file on October 1.  
Thereafter, each time any RBN node-op who starts the Aggregator to 
connect to our server and hasn't yet done so will be prompted to 
download the new pattern file, and take a few seconds to be fully 
up-to-date.


-- 
73, Pete N4ZR
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