[Skimmertalk] Bad Skimmer Spots

Pete Smith n4zr at contesting.com
Fri Feb 4 13:18:21 PST 2011 

I thought everyone might enjoy seeing a little slice of actual RBN data, 
from a small part of the first minute of February 3 (Z time):

callsign 	de_pfx 	de_cont 	freq 	band 	dx 	dx_pfx 	dx_cont 	mode 	db 	date
DK9IP 	DL 	EU 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	15 	2/3/2011 0:00
G4HSO 	G 	EU 	3523.9 	80m 	E77AW 	E7 	EU 	CQ 	28 	2/3/2011 0:00
DL2CC 	DL 	EU 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	30 	2/3/2011 0:00
S50ARX 	S5 	EU 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	34 	2/3/2011 0:00
SV8RV 	SV 	EU 	3523.9 	80m 	E77AW 	E7 	EU 	CQ 	22 	2/3/2011 0:00
ES5PC 	ES 	EU 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	26 	2/3/2011 0:00
ES5PC 	ES 	EU 	7014.2 	40m 	OK2KJU 	OK 	EU 	CQ 	20 	2/3/2011 0:00
WZ7I 	K 	NA 	7014.2 	40m 	OK2KJU 	OK 	EU 	CQ 	16 	2/3/2011 0:00
SV8RV 	SV 	EU 	7014.2 	40m 	OK2KJU 	OK 	EU 	CQ 	32 	2/3/2011 0:00
DL0LBS 	DL 	EU 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	22 	2/3/2011 0:00
OL5Q 	OK 	EU 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	22 	2/3/2011 0:00
HB9SOF 	HB 	EU 	3523.9 	80m 	E77AW 	E7 	EU 	CQ 	11 	2/3/2011 0:00
K8ND 	K 	NA 	7011 	40m 	LZ2VU 	LZ 	EU 	CQ 	19 	2/3/2011 0:00
UA9CLB 	UA9 	AS 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	9 	2/3/2011 0:00
WA7LNW 	K 	NA 	7029 	40m 	K7DCG 	K 	NA 	CQ 	29 	2/3/2011 0:00
NC7J 	K 	NA 	7029 	40m 	K7DCG 	K 	NA 	CQ 	23 	2/3/2011 0:00
N7TR 	K 	NA 	7029 	40m 	K7DCG 	K 	NA 	CQ 	39 	2/3/2011 0:00
K3LR 	K 	NA 	7029.1 	40m 	K7DCG 	K 	NA 	CQ 	17 	2/3/2011 0:00
VA7DZ 	VE 	NA 	7029.1 	40m 	K7DCG 	K 	NA 	CQ 	20 	2/3/2011 0:00
TF3Y 	TF 	EU 	3523.8 	80m 	E77AW 	E7 	EU 	CQ 	12 	2/3/2011 0:00

As you can see, a legitimate station can easily get as many as ten spots 
from different Skimmers, in a single minute, even on a mid-week 
non-contest day.  What we really need is both de-duping (same frequency, 
same callsign, same minute) and de-junking (10 spots on a frequency, 9 
calls spotted the same, same minute, one different).  We think the RBN 
can develop means to take care of the second.  N1MM Logger and CC User 
are already taking care of the first.

CC user is a neat piece of middleware for those whose clients haven't 
yet caught up.  I *believe*, but can't swear, that its de-duping works 
with all cluster node software, not just VE7CC's.  Lee, can you confirm 
this?

73, Pete N4ZR

The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000



On 2/4/2011 12:36 PM, Igor Sokolov wrote:
> David, I am not aquainted with arc-6 but what you describe is pretty 
> close to what I need.  I need to be able to choose either cluster 
> spots or skimmer spots or both. Preferably with separate filtering for 
> each of the two. For skimmer spots I need additional filtering based 
> on the number of skimmers generating spots for the same call (choose 
> 2, 3 or even 4) plus filtering based on master.dta. Having been able 
> to choose all these filters in any combination would be ideal.
> CC client has a very good user interface which allow user not to 
> remember all those filtering commands required by cluster software. 
> Adding filtering described above to CC software using the same easy 
> user interface would be a great advantage.
>
> 73, Igor UA9CDC
> ----- Original Message ----- From: "K1TTT" <K1TTT at ARRL.NET>
> To: <n4zr at contesting.com>; "'Igor Sokolov'" <ua9cdc at gmail.com>
> Cc: <Skimmertalk at contesting.com>
> Sent: Friday, February 04, 2011 7:11 PM
> Subject: RE: [Skimmertalk] Bad Skimmer Spots
>
>
>> That is why arc-6 is passing all the rbn spots on to the client, so 
>> duping
>> and filtering can be done by the user.  You might also want to check out
>> some of the new filters, in the latest beta update there is a number of
>> times spotted filter, so you can limit the rbn spots you see to ones 
>> that
>> have been spotted 2 or more times, and there is also a master.dta 
>> filter to
>> only see spots in the supercheck database... Those filters can be 
>> combined
>> in statements like:
>>
>> not skimmer or (skimmer and unique > 2) or (skimmer and master)
>>
>> Which would give you all non-skimmer spots, plus skimmer spots that are
>> spotted more than twice on the same band within 10 minutes, plus skimmer
>> spots that are in the master.dta file regardless of how many times 
>> they are
>> spotted.
>>
>>
>> David Robbins K1TTT
>> e-mail: mailto:k1ttt at arrl.net
>> web: http://www.k1ttt.net
>> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>>
>>
>>> -----Original Message-----
>>> From: Pete Smith [mailto:n4zr at contesting.com]
>>> Sent: Friday, February 04, 2011 13:38
>>> To: Igor Sokolov
>>> Cc: Skimmertalk at contesting.com
>>> Subject: Re: [Skimmertalk] Bad Skimmer Spots
>>>
>>>
>>> There is a third possibility, but the problem is a little
>>> trickier than
>>> I had thought.  Here's an excerpt I just sent to someone on
>>> another list:
>>>
>>> "As for the theoretical error rate, let's take an example.
>>> Say you have
>>> N6NC CQing for an hour and being heard by 10 RBN Skimmers.
>>> Each Skimmer
>>> will spot you correctly 5-6 times (every 10-12 minutes).  But if some
>>> local event - transmitter splatter, QRN, QRM (especially things like
>>> clicks from a loud adjacent station) causes a mis-spot, then
>>> whichever
>>> Skimmer that mis-spotted you will immediately send out a bad spot.
>>>
>>> Say just one of the Skimmers listening to you sends one bad
>>> spot of you
>>> in that hour. That's 1 bad spot.  Meanwhile, the good spots are being
>>> filtered out as dupes by client software, so that clients are only
>>> receiving 5-6 good spots of you.  Holy cow, that's a 16-20 percent
>>> apparent error rate.
>>>
>>> It's the aggregation, which is why the RBN has to come up with a
>>> solution.  This is a fairly tricky problem, because the system has a
>>> built-in preference for new spots, whether good or bad.  The
>>> bad spots
>>> can come at any time when you are CQing.  Meanwhile, the good
>>> spots will
>>> tend to cluster, because most people who spotted you
>>> correctly will have
>>> done so within a few seconds of your first CQ, and then at
>>> 10-12 minute
>>> intervals thereafter.  I don't know just how this one will be solved,
>>> but I think it can be.  The devil, as usual...
>>>
>>> 73, Pete N4ZR
>>>
>>> The World Contest Station Database, updated daily at
>>> www.conteststations.com
>>> The Reverse Beacon Network at http://reversebeacon.net, blog
>>> at reversebeacon.blogspot.com,
>>> spots at telnet.reversebeacon.net, port 7000
>>>
>>>
>>>
>>> On 2/3/2011 11:38 PM, Igor Sokolov wrote:
>>> > Lee, I think it would be excellent if VE7CC client software
>>> could have
>>> > filtering and validation facilities. There were so many
>>> broken spots during
>>> > CQWW 160 that filled the entire band map and their
>>> percentage was reaching
>>> > 80% on the last night of the contest.
>>> > I see two methods of validating spots:
>>> >   1) pass the spot if the call has been mentioned by 2 or 3
>>> other skimmers
>>> > 2) Pass the spot if it is in the master. dat file.
>>> > Combination of these two would probably cut the number of
>>> broken spots to
>>> > acceptable figures.
>>> > I think telnet client software is the best place for
>>> filtering (better then
>>> > filter in the logger or at the skimmer)
>>> >
>>> > 73, Igor UA9CDC
>>> > ----- Original Message -----
>>> > From: "Lee Sawkins"<ve7cc at shaw.ca>
>>> > To:<Skimmertalk at contesting.com>
>>> > Sent: Friday, February 04, 2011 3:12 AM
>>> > Subject: [Skimmertalk] Bad Skimmer Spots
>>> >
>>> >
>>> >> Here is a small subset of bad skimmer spots. I am looking
>>> at a full feed
>>> >> from the RBN.
>>> >>
>>> >> These are only spots for USA calls that have not been
>>> issued.  Many times
>>> >> the first letter of a call is missing.  Many of these are
>>> actually Italian
>>> >> calls with the "I" missing.
>>> >>
>>> >> http://www.bcdxc.org/ve7cc/notissue.txt
>>> >>
>>> >> I will update the list from time to time.
>>> >>
>>> >> CC Clusters drop these bad calls.
>>> >>
>>> >> There are many other non USA calls that are wrong which
>>> also have the
>>> >> first
>>> >> letter missing. These are harder to find.
>>> >>
>>> >> Other bad calls occur when the last letter is missing or
>>> truncated or is
>>> >> added
>>> >> +in error.
>>> >>
>>> >> "E" and "T" seem to be the most often added bad letters.
>>> >>
>>> >> Lee
>>> >> _______________________________________________
>>> >> Skimmertalk mailing list
>>> >> Skimmertalk at contesting.com
>>> >> http://dayton.contesting.com/mailman/listinfo/skimmertalk
>>> > _______________________________________________
>>> > Skimmertalk mailing list
>>> > Skimmertalk at contesting.com
>>> > http://dayton.contesting.com/mailman/listinfo/skimmertalk
>>> >
>>> >
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>>
>>
>
>
>

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