[CQ-Contest] Busted Reversed Beacon Network spots

Pete Smith N4ZR n4zr at contesting.com
Sat Jun 15 17:00:36 EDT 2013

Bret, the error rate you detect is much higher than anything that we've 
seen. We're all working from the same data, so
if you would like to share the queries you used in arriving at these 
conclusions, we'd appreciate the chance to look at the data through the 
same lens and try to understand the results.

73, Pete N4ZR
Check out the Reverse Beacon Network at
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.

On 6/15/2013 10:17 AM, Brett Graham wrote:
> Admission of a little over one-per-minute wrong-freq-same-band RBN 
> spots at 
> http://lists.contesting.com/pipermail/skimmertalk/2013-April/001149.html 
> prompted me to finish the queries I started working on back in 2011 to 
> find all the bogus-frequency spots on RBN - a project I started when 
> like HB9CVQ, somebody else noticed RBN spotting him somewhere he 
> wasn't transmitting & unlike HB9CVQ, was worried he was transmitting a 
> fecal signal as he didn't know if his transmitter was clean or not.
> Fecal signals we have been told are one of the reasons for 
> bogus-frequency spots on RBN.
> DJ7WW subsequently mentioned ON5KQ's skimmer.  It, along with most of 
> the other skimmers, were making bogus-frequency spots in the 
> 2013-03-08 RBN spot data I have been working with most recently:
> 81 skimmers spotted at least once the same call within one minute as 
> another skimmer spotted that call - but on a frequency >1 kc away but 
> still on the same band where the other skimmer spotted it.  That was 
> 87% of all skimmers QRV that day.  Total of these wrong-freq-same-band 
> spots: 5962.
> 69 skimmers spotted at least once the same call within one minute as 
> another skimmer spotted that call - but on a different band. That was 
> 74% of all skimmers QRV that day.  Total of these wrong-band spots: 885.
> There were 175584 RBN spots that day - excluding DXpeditions & special 
> event calls - stations potentially on >1 band or >1 frequency on the 
> same band simultaneously.  Being a weekday, deliberately fecal signals 
> from dodgy contesters should have been largely avoided.  The total of 
> bogus-frequency spots were just shy of 3.9% of the total of the data 
> set as described - nearly twice the high end of the range I had first 
> suggested I thought it might be.
> Who knows, maybe when diluted with the additional activity during a 
> contest that rate does go down.  And/or maybe there is something to 
> the chatter about skimmers not hearing so well stations during 
> contests that they seem to hear the rest of the time.  Certainly not 
> me, having previously been involved in developing, debugging & 
> deploying SDRs & the pay-TV platforms they received long before 
> skimmer appeared!
> Anyway, on that day there were on average nearly five bogus-frequency 
> RBN spots each minute.  The data has been there for anyone without 
> confirmation bias to download & see for themselves.
> The receiver performance reference mentioned below, as noted by DJ7WW, 
> is irrelevant - though the product itself is an excellent example of 
> another reason we keep being told is behind wrong-band-same-freq RBN 
> spots - though most of those spots come from skimmers that are not 
> using receivers of the type we have been told are the culprit.
> -ex-VR2BG/p.
>> Interesting - I "admitted" what? That there are a lot of Softrock-type
>> receivers on the RBN, some of which have inadequate I/Q image
>> reduction? Sure. That direct downconversion receivers like the QS1R
>> occasionally throw what look like I/Q spots, even though there is no
>> simple explanation. Sure. I saw mine throw one of those just
>> yesterday. Wish I knew why.
>> The RBN teamis actively working on a promising technological solution to
>> get rid of all of thisclass of busted spots.
>> Wrong-band spots are quite another creature. I'm still waiting for data
>> on these, but think that either inadequate harmonic suppression and/or
>> intermod will be shown to be the source. If that's the case, then the
>> receiver used probably makes little difference.
>> Bret, before you attack SDR receiver performance indiscriminately, take
>> a look at Rob Sherwood's review of the KX3.
> _______________________________________________
> CQ-Contest mailing list
> CQ-Contest at contesting.com
> http://lists.contesting.com/mailman/listinfo/cq-contest

More information about the CQ-Contest mailing list