[CQ-Contest] Summarizing the Skimmer Accuracy Thread

[Pete Smith N4ZR]

It also needs to be kept in mind that with rounding taking place at the 
sending Skimmer's Telnet server, an actual calibration difference of 
only a couple of Hz can lead to spots being 0.1 KHz apart.  This isn't 
just a Skimmer issue - in fact, any spotting mechanism that readsthe 
receiver's frequency can be off by even more - for example, I use a 400 
Hz filter to run, and frequently tweak my main tuning control to get out 
from under a packet pileup.  Any spot I then make can easily be 0.2 KHz 
or more different from others' spots of the same station.

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 9:54 PM, Jim Jordan wrote:
> 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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