Re: 6m grid false positives in Spot Collector


Dave AA6YQ
 

+ AA6YQ comments below

I'm having a problem with false FT8 positives firing off alerts.

I grid chase (and DXCC chase) on 6m. With my cluster connections up and WSJT and JTAlert-x connected, I get frequent hits for stations where the grid information is incorrect. I'm not talking about "gibberish spots" here, but legitimate spots that trigger incorrectly.

+ If you're using JTAlert, then JTAlert is the source of the gird information.


The source, according to Spot Collector, is my own copy of WSJT-x. There have been numerous examples of a spot arriving via WSJT-X with one (ostensibly) correct grid, but it shows up in the DX Grid column in S.C. with a different grid, causing alerts to sound. I could understand if this was a station I'd worked previously and an old grid was being auto-populated, but this happens even with stations I've never worked before.

One such station CQs on FT8 from grid EM31, a grid I have previously worked, confirmed via LoTW, and verified for VUCC credit. The station shows up correctly in WSJT and JTAlert-X, but in DX Base it's showing this particular station as EM43, one of only two EM grids I've never worked.

+ I can't help you with DX Base, Peter.


This isn't the only circumstance, but since the op in question (AC0RA) is an avid 6m operator with a good signal to me, alerts on his call are frequent. But with many others the same thing is happening. JTAlert-x/WSJT has the grid correct according to the CQ sent by the originator, but S.C. gets it wrong.

+ SpotCollector receives spots from JTAlert, but also from your other spot sources. If you have SpotCollector configured to capture location information from spot notes, then it's possible that a Spot Database entry created by JTAlert with one grid square gets updated with a different grid square from a subsequent cluster spot. To see if this is happening,

1. enable "Record individual spot information" (Configuration window, "Spot Database" tab)

2. when encounter a Spot Database Entry with what appears to be an incorrect grid square, right-click it, and select "Display spots of"; a window bearing all spots of the Entry's station will appear.


Now, if this isn't already the case, I would respectfully suggest than any incoming spot for a station previously worked that has grid information populated by the FT8 software, that information needs to override any previous grid info from past QSOs in DXKeeper. Obviously this would be especially needed for Rovers. I have a suspicion that this is already the case, but I wanted to mention it here just in case. But with that said, I'd really like to understand why I'm getting so many false positives.

+ Most users do not have a computer fast enough query their log for previous QSOs with each incoming spot.


And speaking of false positives, when the inevitable gibberish print from WSJT causes a "need" alert is JTAlert (and subsequently in Spot Collector), is there any way to maybe put in a lookup or truth table, etc, within S.C. so I won't get woken up by a badly interpreted FT8 "spot"?

+ No:

1. there is no database that specifies an award-accurate grid square for amateur radio station (DXLab's USAP database only contains callsigns issued by the US FCC, and the grid squares are not award-accurate because they are computed from the centroid of the station's zip code)

2. even if such a database existed, some stations operate from non-home locations


Or some way to say "only alert if X number of "new grid" or "new zone" (etc) spots are received within Y minutes? I'd typically want to set that at 3 within 1 or 2 minutes personally.

+ The mechanism required to implement this would require significant development effort, but most users want to be immediately notified if a needed station might be QRV and thus would not utilize it.

73,

Dave, AA6YQ

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