Yes, I should have made it clear that the 2dB signal level is to maximize close by planes. IE usually to pick up the most ground positions near an airport.
Due to the ADSB messages are amplitude modulated the decoder software can does work on messages close to the max signal level but not so much near the smallest signal level. Max signal are clipped a still decodable. While small messages get lost in the noise level.
The sweet spot for receiver is the -2dB to -35dB range, there is still a chance to decode messages outside this range. If you move the sweet spot closer (the inner part of the donut) you also lose a lot of the far away signals (outer part of the donut).
In my experience at max gain the inner range is around 3-4km and the outer range is 350-400km.
If you lower the gain to around 20 the inner range is less than 1km and the outer range drops to about 200km or less. So you are giving up a large amount of your far range to be able to see those 1km or less planes. You are giving up 150km far to get 3 km closer detection. There aren’t many cases you want to do this unless you are near an airport and looking for planes on the ground.
Most of the discussions on the forums about gain settings are to maximize messages decoded per second. This includes the automated scripts for best gain.
The original question I was trying to answer was why someone is missing planes on the ground. You need the gain low + you need the receiver location to be set.
I forgot to mention one more thing. Old receivers (8+ years ago) had a huge donut effect. The minimum detection range was around 15km and their max range was around 200km. And they cost in about $600.
Today the receivers don’t have a noticeable donut effect (3km to 400km decodable range) and they cost $20.
I would just set the gain as high as possible and not worry to much about missing the very few close by messages unless you really need them.
Here is a lot of discussion about gain and number of messages detected.
That was in the ac_counter.php file. insert your coordinates in place of the ones already in the code. You will have to convert DEG MIN SEC to a decimal figure. Because I am in Australia I have to use a (minus symbol) i.e., -38.303028 deg latitude.
you just have to set your lat and lon in dump1090 properly - then ac_counter.php fetches the data from the aircraft.json file. warrnamboolcity is right when he mentions that there are locations with negative values - maybe yours too. but he probably mixed up with the other script (radar.php) where to insert coordinates - in ac_counter.php there is no need to set coordinates …
Sorry, but I think I am missing something here, your script looks in receiver.json for the lat, lon. Looking at that file there is the correct lat & lon for my location in Tasmania, Australia, yes a negative lat.
No. The wheel sensor method is virtually non-existent in small GA. There are two methods allowed for automatic change from ALT to GND. One is a wheel weight sensor. It’s often used on transport category aircraft. The other methods is air speed. Once you drop below a set speed, it automatically changes to GND. That speed is based on the specific aircraft that system is in.
George Town! Tassie is a nice place. Do you do Raaus instruction?
It might pay to goto to file path where the original ac_counter.php is and confirm it is there. Then delete the one you made executable in the /Pi directory. CP (copy) the original ac_counter. php back into the /Pi directory, add the relevant numbers then make it executable with chmod… I reckon I had the same problem from memory and this is what I did. I reckon once you make a file executable it is like a bride wearing white the second time around. You can’t change it back to something it once was.
I am presuming here you made the file executable then made last Lon changes??
I’ve noticed that from 13th October 2018 I’ve lost all first altitude and last altitude information from my daily log .xls spreadsheet. I’ve made no changes to my Raspberry Pi in over six months. PiAware Skyview is still working correctly. On my FR24 Feeder Tracked Aircraft List it still shows aircraft altitude is being picked up for FlightRadar 24 and within the “Flights with Positions From This Feeder on FlightAware.com Within the Last Hour” section on my FlightAware stats page Altitude is still being shown.
Thanks for information, I tried it early yesterday morning and the first altitude and last altitude columns are still blank. The other columns are working as expected.
Thank you for the help, I added it under the “tisb” isset initially but I’ve just changed it, so I will have to wait until midnight to make sure it works correctly now.
