British Forum > OGN-R PilotAware
New PAW / OGN station seems to be deaf to FLARM?
Admin:
Hi Kev
Looks like the quality of reception is very low power
you did pick up some gliders today, here are your traces
http://flarmrange.onglide.com/#EGBKE,max,all,52.3227_-0.7062,11,#00990000:#009900ff,circles;
Compare this to everybody today overlapping your receiver
http://flarmrange.onglide.com/#,max,today,52.340533_-0.734696,10,#00990000:#009900ff,circles;
And the same for PilotAware reception
http://flarmrange.onglide.com/#PWEGBKE,max,today,52.3227_-0.7062,10,#00990000:#009900ff,circles;
Versus everybody
http://flarmrange.onglide.com/#PW%,max,today,52.3227_-0.7062,10,#00990000:#009900ff,circles;
Could be many reasons, Antenna location, cabling ...
Thx
Lee
Kevin W:
Thanks Lee,
Yes I saw some of the traffic come through today, and am starting to understand the two different 'receivers' in OGN terms (PW and non PW).
The PAW aerial I am not surprised, at the moment it is just next to me in the study. The FLARM aerial is a bit more disappointing, being an X50 on a mast - but I guess that's the problem with a non-tuned aerial, with probably getting on for 10m of coax (all be it seriously thick stuff) before the SDR.
I also need to appreciate the difference between ADSB and Flarm traffic - I get 'great' ADSB rx from the X50, but there is a lot more of it, it is broadcast with at least 25 watts, and lots of it is broadcast from a much higher altitude - all very different to FLARM!
Working on plans for getting a PAW and FLARM specific aerial outside above the roof line....
Cheers
Kev
exfirepro:
Kev,
OK, first thing, although your X50 is 'off frequency' for FLARM traffic, for receive only there shouldn't be a vastly significant difference in performance, though the OGN collinear will obviously be better. My station (PW) Balerno is running in my loft on a 9dBi collinear and receives gliders out to about 80Km (across on the north side of the Edinburgh CTA).
Of more significance is the fact that 1090 MHz signals are significantly stronger than 25 Watts. They generally vary from about 70 Watts for older GA transponders up to 500 Watts at the antenna for Commercial mode S /ADSB, so up to 50,000 times stronger than the 'average' 10mW FLARM transmission.
That still doesn't account for the extreme difference between your PAW/OGN station and all the others around you though, so we need to get to the bottom of what is going on.
First thing is to minimise coax loss by moving the SDR dongle up as near as possible to the antenna and using a USB cable to transfer the data from the SDR down to the Raspberry Pi. If the cable length is 5 metres or more, make sure to use an 'active' USB cable.
It's also worth moving the Raspberry Pi up closer to your antenna location as this will shorten the length of your P3i transmit antenna co-ax, thereby minimising transmission losses. Longer Ethernet cables aren't usually a problem.
It would definitely be worth trying to get your antennas outside, though mine are still running inside my loft with a concrete tiled roof as the station is still primarily 'experimental' and local PAW traffic levels are very low compared to 'down south'.
Hope you get things sorted out.
Regards
Peter
Kevin W:
Hi All
I am pleased to say my OGN-R station is no longer deaf! :) It is far from perfect, but it is now above my 'silver foil insulation' lined loft conversation and just has tiles between it and the outside world. I am working on getting the aerial outside, but that is harder to do!
A question though, flarmrange.onglide.com seems to be showing both FLARM and PAW traffic that my station has seen, that is not shown on the overall coverage map.
For example , in the picture below I saw quite a bit of PAW traffic just south of me over Wellingborough:
https://imgur.com/qU8gYNS
but in the overall view it doesn't exist:
https://imgur.com/JXSpxn2
and the same for FLARM, I saw traffic over Wellingborough and to the North of Earls Barton:
https://imgur.com/2cSKpFr
that isnt seen on the full view:
https://imgur.com/WVbH9Rn
For the purposes of these images I have made the normal 'light green' much darker, to make sure it isn't just that it is so light green it can't be seen.
Any ideas?
Cheers
Kev
Keithvinning:
Are they both reporting for the same timeframe? Just a thought
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