[CQ-Contest] Implementing a Dynamic error free RBN-Skimmer network
Hans Brakob
kzerohb at gmail.com
Wed Jul 17 16:52:46 EDT 2013
I would be in favor of an RBN feature which deliberately introduced random suffix errors into the output stream.
73, de Hans, K0HB
On Wed, Jul 17, 2013 at 4:38 PM, Igor Sokolov <ua9cdc at gmail.com> wrote:
> Very well done Jose. Thank you much. I have enjoyed reading it.
> Couple of thoughts came to my mind.
> There are instances where one station can be heard on several frequencies.
> 1) Stations with parasitic AM modulation can have 3 signals spaced aprox.
> 1.5 kHz
> 2) Second and third harmonic signals.
> 3) Multy/ Multy stations.
> How does your algorithm treats these cases?
> 73, Igor UA9CDC
> ----- Original Message -----
> From: "José Nunes CT1BOH" <ct1boh at gmail.com>
> To: <cq-contest at contesting.com>
> Sent: Tuesday, July 16, 2013 4:23 AM
> Subject: [CQ-Contest] Implementing a Dynamic error free RBN-Skimmer network
> The purpose of this post is to present a way to implement a dynamic error
> free Skimmer-RBN/Packet network that automatically:
> 1. Flags and eliminates “Busted Spots” from the network
> 2. Flags and eliminates “wrong frequency” spots from the network
> 3. Prevents inaccurate Skimmer-Spotters from feeding incorrect spots to the
> network
> 4. Eventually allow the Skimmer-RBN users to customize reception of spots
> according to the quality flag and several parameters of the algorithm
> In my various CQWW CW operations since 1989
> http://www.qsl.net/ct1boh/operations.htm I’ve only enjoyed
> Skimmer-RBN/Packet networks from the pile-up end side as PY0F, P40E, CR3E,
> etc.
> Skimmer-RBN and packet network has been a blessing for the DX operator as a
> constant pile-up generator and a reason for the never ending increase in
> total QSO number throughout the years.
> Recently, building the idea of operating Assisted on CW from a DX location
> for the first time, I begun to study how to correctly use
> Skimmer-RBN/Packet networks. Operating Assisted in minor Contests from
> home, I discovered several problems that made the use of callsign and
> frequency information from a RBN feed band map not 100% reliable:
> - Busted spots
> - Non-existent spots on a particular frequency
> - Small frequency shifting spots and
> - “Unstable” band map with callsigns alternating, popping-in and popping-out
> Wanting to use Assistance and not being able to completely trust the
> information is a strange concept to me. If I use Assistance I would expect
> not to waste time in my mind processing if the call in the band map is good
> or bad.
> Solving the problems requires a system that is able to automatically assess
> the spot before send it to the network and “learns” from itself. The
> solution is a dynamic error free RBN-Skimmer algorithm.
> Studding RBN data that can be downloaded here
> http://www.reversebeacon.net/raw_data/ I came to a solution. The algorithm
> I propose has a simplicity beauty and works extraordinary well. For every
> new spot that is provided to the Reverse Beacon Network by a Skimmer
> Spotter or by a packet network by a human, the system will automatically
> generate the following “Quality Tag” for each spot:
> Good Spot
> Good Call, New Frequency Spot?
> Busted Spot
> ? Spot
> In short, the algorithm can be described as follows:
> Any new spot will be tagged as a “Good Spot” if looking back 25 minutes
> there are two more Spots with the same call as the new spot, in the
> approximate same frequency (+/- 0.3 Khz)
> Any new spot will be tagged as a “Good Call, New Frequency Spot?” if
> looking back 25 minutes there is a Spot that was already tagged as “Good
> Spot”, with the same call as the new spot, but the new spot is in an
> adjacent frequency (less or equal than -0.4 Khz and greater or equal than
> +0.4 Khz)
> Any new spot will be tagged as “Busted Spot” if looking back 25 minutes
> there are at least three already tagged “Good Spot” with a similar call, in
> the approximate same frequency of the new spot (+/- 0.1 Khz). The similar
> call is a call that can be transformed into the new spot call by character
> insertion, deletion or substitution.
> Any Spot that is not a “Good Spot”, a “Good Call, New Frequency Spot?” or a
> “Busted Spot” is an undetermined spot “?Spot”.
> Let’s have a closer look at it, with examples from RBN spots from CQWW CW
> 2012:
> “Good call” quality flag
> #1 call1 freq1 time1 #Spotter Quality tag
> 711 CR3E 7045 4 #G4HYG ?Spot
> 860 CR3E 7045 5 #WB8BIL ?Spot
> 918 CR3E 7045 5 #WB2LSI Good Spot
> 3077 CR3E 7045 20 #G4HYG Good Spot
> 3254 CR3E 7045 21 #S52AW Good Spot
> 3336 CR3E 7045 22 #KB9AMG Good Spot
> 3892 CR3E 7045 25 #DK9IP Good Spot
> …
> CR3E started the contest (CQWW CW 2012) on 7045. The first two spots get
> the quality flag “?Spot”, but by the third spot of WB2LSI skimmer CR3E is
> flagged as a “good call” and all subsequent spots on 7045 will get the
> “Good Spot” quality flag.
> After a lot of testing I can say the system should operate with a bandwidth
> filter of +/- 0.3 KHz. All spots that do not fall within this +/- 0.3 KHz
> filter will not get the “Good Spot” quality tag.
> “Good Call, New Frequency Spot?”
> #1 call1 freq1 time1 #Spotter Quality tag
> …
> 33721 CR3E 7045 220 #F5MUX Good Spot
> 34154 CR3E 7041.3 223 #KA9SWE Good Call, new freq?
> 34460 CR3E 7045 225 #RU9CZD Good Spot
> …
> 40711 CR3E 7044.9 261 #KQ8M Good Spot
> 40740 CR3E 7041.3 261 #KA9SWE Good Call, new freq?
> 41213 CR3E 7045.1 264 #K3LR Good Spot
> …
> CR3E continues to be on 7045. All of a sudden #KA9SWE skimmer spots CR3E on
> 7041.3. The systems detects a frequency difference and flags it as a “Good
> call, new frequency?”. Is it really a QSY to a new frequency by CR3E? If
> yes, then, shortly after two more spots the system will change the flag to
> “Good spot”. It is not the case in this example because skimmer #RU9CZD
> confirms there was no QSY. Later on we see that #KA9SWE sends another spot
> on 7041.3.Obviously #KA9SWE skimmer needs frequency calibration.
> After a lot of testing I can say the system should operate with a bandwidth
> filter of greater than +/- 0.3 Khz. All spots that do not fall within this
> +/- 0.3 KHz filter will not get the “Good Spot” quality tag, and this
> should be the accuracy threshold.
> “Busted Spot”
> #1 call1 freq1 time1 #Spotter Quality tag
> 31159 CR3E 7045 204 #S52AW Good Call
> 31172 KR3E 7045 204 #K9QC Busted
> 31205 CR3E 7045 205 #G4HYG Good Call
> …
> CR3E continues to be on 7045. All of a sudden #K9QC skimmer sends a KR3E
> spot. The system detects that KR3E is a similar call of CR3E on the same
> frequency of a Good Spot and it will flag this spot as a Busted spot. The
> system uses Levenshtein distance to calculate a similar call (
> http://en.wikipedia.org/wiki/Levenshtein_distance). Depending on the
> length of the callsign it will look for calls that are x-off letters away.
> After a lot of testing I can say the system should operate with a bandwidth
> filter of +/- 0.1 Khz. A Busted Spot comes from a good spot, and usually
> from Skimmer that has already spotted the call, therefore a threshold of
> 0.1 is what works best.
> “?Spot”
> All “?Spot” are spots that cannot be determined as “Good Spot” or as “Good
> Call, New Frequency Spot?” or as “Busted Spot”. Some are good spots – The
> first and the second spot on a new frequency when a run starts. But the
> majority is “spots” send by skimmers, of stations calling RUN stations.
> These spots should never be sent out to the network by skimmer. They are
> false positive running stations.
> How does this proposed system works?
> I can say it works extraordinary well!
> I tested all 40 meter spots from CQWW CW 2012 – almost a million sots:
> Quality flag Spots % of spots
> ? 46.593 4.69%
> Busted 20.734 2.09%
> Good Call 855.227 86.08%
> Good Call, new freq? 70.994 7.15%
> Grand Total 993.548 100.00%
> After running my algorithm I also went back to validate both “? Spots” and
> “Good call, new freq?” spots. If I have the following spots:
> 711 CR3E 7045 4 #G4HYG ?Spot
> 860 CR3E 7045 5 #WB8BIL ?Spot
> 918 CR3E 7045 5 #WB2LSI Good Spot
> It is easy to determine after running the algorithm that spot #711 and
> spot#918 are “Good Spots” from spot 918. This cannot be done with a real
> time system, because once a quality tag is given to a spot it is given.
> Of the 46.593 spots with “?Spot” quality flag:
> 20768 are good calls (these are all the first and second spot of a run
> that just started)
> 25825 spots are indeed “? Spots” (mostly stations calling on pile-ups)
> Of the 70.994 spots with “Good Call, New Freq?” quality flag:
> 24.502 are good call (these are all the first and second spots of a
> run that just started in a new frequency)
> 46.492 spots are indeed “Good Call” that are sent to the network with
> a wrong frequency by an uncalibrated skimmer.
> My algorithm also allows the RBN to detect uncalibrated skimmer spotters.
> Looking at the list of skimmers it is easy to build a list based on the %
> of “Good call, New freq?” quality flag. Let’s take a look at the top ten
> Skimmer spotters according to spots sent to the RBN:
> Skimmer Spots % of “Good Call, New Freq?”
> #K3MM 45.726 3.1%
> #GW8IZR 29.984 8.7%
> #S52AW 29.214 5.2%
> #DL8LAS 26.906 3.7%
> #DR1A 25.831 3.1%
> #RU9CZD 24.301 6.4%
> #HA6PX 23.317 38.6%
> #OL5Q 23.006 4.4%
> #W3LPL 21.889 2.0%
> #KQ8M 21.833 7.1%
> We can see that a calibrated skimmer should not have more than 3% of “Good
> Call, New frequency?” spots, because that is the dynamic of people changing
> frequency in the contest. Numbers greater than that show uncalibrated
> skimmers, such is the case of #GW8IZR, #HA6PX, or #KQ8M.
> To finalize several considerations:
> 1 RBN (Reverse Beacon Network) is a fantastic instrument for contesters and
> DXers.
> 2 We have the instruments to turn the current RBN network into a dynamic
> error free system
> 3 The system should allow the user to decide to filter out “Busted” spots,
> “Good call, New Freq?” spots and “? Spots”. By giving a quality flag it
> would be up to the user to use the quality flags to filter out spots
> 4 The system should warn uncalibrated skimmers
> If you want to play with the data and with the algorithm you can:
> The algorithm and several graphs that explain how well the system works is
> available to download here
> http://www.qsl.net/c/ct1boh//dl/
> Please note that the excel file is ~90MB
> In sheet 1 there are 993.548 spots from CQWW CW 2012 on 40 meters
> In sheet 2 there is the results of the algorithm. This would be the output
> of the system with real time adding a quality flag to each spot (if you do
> Alt-Q you will activate the macro. it takes 1892 seconds to flag all
> 993.548 spots on my PC. Or on average 0.0019 seconds to flaf every incoming
> spot.
> In sheet 3 there is a pivot table to manipulate data from sheet 2
> In sheet 4 there is a list and graph that show the performance of skimmers
> as far as frequency calibration is concerned
> In sheet 5 there is a list and a graph of calls and the % of Busted of each
> call according to number of spots
> In sheet 6 there is the algorithm code (please note that I’m not a
> programmer. I just learned VBA to do this)
> --
> José Nunes
> CONTEST CT1BOH - http://www.qsl.net/ct1boh
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