[CQ-Contest] Summarizing the Skimmer Accuracy Thread

[Jim Jordan]

There are two explanations for reported frequency variations unless they are 
reported at EXACTLY the same moment in time--rx error or tx change. Many run 
stations, myself included, if that less than perfect run frequency becomes 
even less perfect we will adjust the tx frequency ever so slightly to try 
and get in the clear. On the next CQ after that another skimmer may pick up 
the new frequency and report that as a new spot or it may be interpreted as 
the same spot but a different frequency. Saw that in ARRL DX CW when I 
shifted frequency while running at NY4A. Not sayin' one way or the other, 
but consider all possibilities.

73,

Jim, K4QPL

----- Original Message ----- 
From: "Pete Smith N4ZR" <n4zr at contesting.com>
To: <vr2bg at harts.org.hk>
Cc: <cq-contest at contesting.com>
Sent: Monday, February 25, 2013 9:35 PM
Subject: Re: [CQ-Contest] Summarizing the Skimmer Accuracy Thread


> Bret, send me your data in a form I can look at, and we can have a useful 
> discussion.  I can imagine several scenarios for what you describe - 
> harmonics, dueling CQs, keyclicks, and so on.
>
> I'd love to see your data.  Your assertion about 1-2 percent errors is 
> totally out of the ball park. The RBN made 3.7 million spots during ARRL 
> CW - are you really saying there were 37,000-74,000 erroneous spots?  Show 
> me!
>
> 73, Pete N4ZR
> Check out the Reverse Beacon Network at
> http://reversebeacon.net,
> blog at reversebeacon.blogspot.com.
> For spots, please go to your favorite
> ARC V6 or VE7CC DX cluster node.
>
> On 2/25/2013 6:33 PM, VR2BrettGraham wrote:
>> Here is some more data.  On 2012-09-21, there were 151 RBN spots of the 
>> same call but on another frequency >3 kc away on the same band at exactly 
>> the same time (to the second) as another skimmer spot. For this query, I 
>> can avoid "dupes", so opening that up to spots of the same call >3 kc 
>> apart on the same band within about 9 seconds of each other finds 369.
>>
>> That is just one mechanism.  Spots of same call on different band on the 
>> very same second look to have been 140.  That's already 0.3% of RBN spots 
>> that day & that will exclude a LOT of wrong-band spots.  Add busted call 
>> spots & who-knows-how-many busted call wrong-band or wrong-freq spots & 
>> then scale all this up by some factor as activity is much higher on 
>> weekends (I'm working with weekday data here, as it makes it easier to 
>> find wrong-band spots as no multi-multis on then) - I believe RBN could 
>> be blowing 1-2% of what it spots, perhaps more.
>
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