Yet another user with MLAT issues


#1

After a long absence, I’ve recently got my ADS-B system back online again. Much better antenna this time around! I’ve noticed like many others here, that mlat is not working, and from reading the posts, this seems related to USB or location issues. I have had it working once but for less than an hour I think. I’ve tried a few usb ports on the computer but that seems to have no effect. I’ve also specified my specific LAT/LONG in on my stats page. One thing I notice that seems odd though, the map in the top right corner of my stats page shows my location in the wrong location (not even close actually). Even after I update it to the EXACT lat/long, it never changes.

I also run an SDRPlay RSP2 on this machine from time to time (SDR Radio), (no, NOT at the same time) with 10 MHz of bandwidth the sdruno app never has a problem passing all that data so I find it hard to believe that USB is the problem, unless I’m missing something?

My hardware: Ubuntu 16.04.3 LTS running on an i5 with 16gb RAM. with an RTL-SDR.com V3 1ppm TCXO sdr dongle.


#2

Your problem is in setting the correct location, currently it’s set to a random spot on an apparently unpopulated hill.

How are you configuring the location exactly? If you are using GPS coordinates, make sure you are using decimal degrees not DMS.


#3

I found a program called usbtop that lets me look at usb traffic. Pretty cool. Bus 2 - Device 3 is the RTL

Bus ID 1 (USB bus number 1) To device From device
Device ID 1 : 0.00 kb/s 0.00 kb/s
Device ID 2 : 0.00 kb/s 0.00 kb/s
Device ID 3 : 14.48 kb/s 8.25 kb/s
Device ID 4 : 0.00 kb/s 0.00 kb/s

Bus ID 2 (USB bus number 2) To device From device
Device ID 1 : 0.00 kb/s 0.00 kb/s
Device ID 2 : 0.00 kb/s 0.00 kb/s
Device ID 3 : 1.21 kb/s 1161.01 kb/s

So while running, the ads-b receiver is doing 1100kb/s out of 480 Mbit/sec max… so well under


#4

It should be doing around 4800kB/s + overhead (assuming a 2.4MHz demodulator) - I suspect you have a measurement error.


#5

I think your right about the data rates being reported by that utility. if I do an rtl_test -s 2.4e6 its 1160kB/sec. If I do rtl_test -s 3.4e6, it reports the same value. Unless I’m not understanding how rtl_test works.

This still does not change the fact the my RSP1 sdr radio with 10mhz of bandwidth works just fine? and that the map on my stats page display the wrong location, which would coincide with the thought that these errors are related t bad location information.


#6

I’m embarrassed to say this but I figured it out. I guess it pays to read ALL the text on a page. When selecting the location on the map from the configure screen, you have to actually DRAG the blue icon to your desired location. That seems to have fixed it. Well. at least it fixed the mlat issues. the Map on my stats page is still not correct.

The other problem I see is that if entering the location manually, via decimal lat/long, it does not seem to update the map location. At least not for me. I actually had to drag that blue icon on the map…

Thanks much - it looks like mlat is up!


#7

It’s an easy mistake to make, the UI is a bit confusing. Good to hear it’s all working now!