[RTTY] Skimmer spots dropped at VE7CC cluster node

[Lee Sawkins]

Since most of the RTTY spots in my dropped lists were listed twice, the actual real number of dropped spots was closer to 20,000 rather than the 37,000 listed. Out of 922,000 RTTY spots over the weekend I was dropping about 2%. A lot of them were not busted, but simply too close to a similar valid call sign. This is how the "Levenshtein distance algorithm" works. Calls that are 60% or greater similar to another call are said to be busted. ie 3 letters the same and 1 or 2 changes will be a busted call. Any 5 letter call beginning with VE7 will be detected as busted if on or almost on my frequency (VE7CC). 

I think it is ok to drop similar calls on or next to a running station. It will help encourage contesters to make sure the frequency is clear before they start CQing. If they don't get any answers to their CQs, they will probably move! I also got a direct complaint from S56A that he was being dropped when he was right next to S51A. This sort of thing happens all the time. 

Lee 

----- Original Message -----
From: "VE3NEA Alex" < alshovk at dxatlas.com > 
To: rtty at contesting.com 
Sent: Monday, October 5, 2015 2:38:28 PM 
Subject: Re: [RTTY] Skimmer spots dropped at VE7CC cluster node 

Hi Jim, 

Your callsign was spotted 273 times on the first day of the contest. It also appeared 41 time on the VE7CC list of the dropped 
spots, but this does not necessarily mean that your call was busted. This just means that another callsign, similar to yours, 
was copied on a frequency close to yours. In 18 cases it was W7DRM, and in another 18 cases it was W7RN. Both callsigns belong 
to the active contesters. Decoding errors are random, it is extremely unlikely that 18 spotters made exactly the same error. 

In the remaining 5 cases, the callsigns were W7CY, W7RYY and DW7GY, which seem to be the busts. Therefore, the error rate for 
your callsign was 5/273 = 1.8%. 

73 Alex VE3NEA 

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