British Forum > OGN-R PilotAware
New ATOM Ground station SDR Detection Issues
Admin:
Hi Kev
What makes you think the FLARM reception stops working ?
Thx
Lee
kevkdg:
Hi Lee,
It seems to periodically (twice now that I'm aware of) to show the FLARM traffic at the local airfield as being rebroadcast from a station much further away (Church Fenton/Leeds East). Then when I reboot the Pi, all the local FLARM traffic starts showing as local again to Rufforth.
I was wondering whether this is corresponding with the RF Noise drops on the following graphs, as the sudden pick up in RF Noise tallies with the two occurrences I became aware of this issue and rebooted the Pi:
3rd April and 17th April. So this is more than a coincidence I suspect, and the drops in RF noise must indicate the loss of FLARM receipt. The reason for which I have no idea!
http://grafana.glidernet.org/d/000000001/receivers?orgId=1&var-receiver=UKRUF
Any ideas? Out of interest, what dates did you push any software updates?
Admin:
Hi Kev
--- Quote ---It seems to periodically (twice now that I'm aware of) to show the FLARM traffic at the local airfield as being rebroadcast from a station much further away (Church Fenton/Leeds East). Then when I reboot the Pi, all the local FLARM traffic starts showing as local again to Rufforth.
--- End quote ---
Interested to know how you determine that
Are you monitoring both stations at the same time ?
I think there may also be some confusion here, so lets clear that up first
if you are referring to the letter 'l' or 'r' on the Front page display, this merely refers to where the last data was received from
it could be local capture (through the RF/SDR), or remote capture (via the GRID) - this data is timestamped, so only the most recent is used internally.
There is a co-ordination from the GRID to tell each ATOM who should rebroadcast, as we do not want to clog the airwaves with un-necessary data. This is quite complicated, but in simple terms lets say, the ATOM(s) closes to the PAW requiring the rebroadcast is chosen - that may not be your ATOM, even though you are closest to the FLARM, you may not be closest to the PAW
In reality, each PAW is informing the ATOMS periodically who it can hear, this is then used as part of the GRID profiling for rebroadcasting, in most cases this relates directly to proximity, but not always - for example, local topography such as buildings, hills etc affect the broadcast in certain directions, the same is try of the aircraft obscuration, if antenna are situated internally to the front or rear
We regularly see a situation where rebroadcast only ever comes from ATOMS at certain directions from a plane, this is usually
due to obscuration either from the perspective of the aircraft, or the ground.
regarding noise - this is completely unrelated, we do not use this information as part of rebroadcast.
--- Quote ---Out of interest, what dates did you push any software updates?
--- End quote ---
I think it was the 4/5 April
thx
Lee
kevkdg:
Hi Lee,
This website shows a dotted line from the aircraft to the receiving station. This is how I could tell all the gliders were being received by Leeds East instead of Rufforth, despite being on the ground a few hundred yards from our station or in the local circuit.
https://www.gliderradar.com/center/53.93709,-1.17451/zoom/11/time/15
Also, looking at the FLARM page for Rufforth it showed that zero aircraft had been received over the past 12 hours, last hour, last minute etc. As soon as I rebooted these numbers went up.
Steve from Leeds East alerted me to the issue on 3rd April, it then happened again and I became aware on 19th April.
Hope this helps.
Kevin
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