ADS-B Radar Question

[JGoodish]

I've been evaluating ADS-B weather over the past couple of weeks, and one of the difference I've noted from XM is how the weather products are delivered. ADS-B appears to stream FIS-B data in small random units of information continuously, so it may take a while to receive all available information for any particular airport.

Radar appears to work the same way. I departed a small rural airport today and was in CRUISE for 10-15 minutes, receiving 2 ground stations, and still did not have the full local radar picture. I had blotches here and there, with "radar unavailable" overlay notes scattered among them on the map. Eventually it all filled in, but even with 5 minute local radar updates, it was probably 3 or 4 of those cycles before I had the full radar picture. That seems like a long time to wait in order to know what's going on around you.

I assume that this all impacted by the number of ground stations received, error rate, etc. I'm not sure how the receiver selects the ground station to listen to, or whether it just accepts streaming data from all of them and displays it on the map regardless of which tower transmitted which piece of data.

For those who have been receiving FIS-B products for a while, how normal is this type of behavior with ADS-B receivers?


Thanks,
JKG

 

[denverpilot]

Sounds like it matches the technical specifications of the system. Can't say how it behaves real-world yet, but it's VERY bandwidth constrained. It's equivalent to 1990's technology as far as RF transmission of data goes.

 

[Piloto]

JKG

Thanks for the report. My hangar neighbor had the same experience with the GDL-39. I think it is the nature of the system and nothing wrong with yours. He was kind of disappointed that could not receive WX on the ground like on my Aera 560 XM\WX with the plane inside the hangar. He was going out that morning when I alerted him of a TFR for the area shown on my 560. A couple times I have postponed engine start due to WX or TFRs shown on the 560. During preflight I turn on the 560 to capture XM\WX data and then after preflight I check the 560 for any SIGMETs or TFRs. Very handy.

José