Hi,
I’ve just set up a new site and I’m a bit flummoxed. My tracks are almost all dotted. This applies to local flights and those 100mi+.
I’m using a pro stick with a 10 element colinear mounted 5m above ground outdoors in a rural setting. No airfields nearby.
I have another site in an urban setting with the same antenna and a prostick plus (for the filter) and have mostly solid tracks at all ranges.
What have I done wrong and how can I fix it?
Thanks in advance
I think it means you are losing reception for more than a fixed amount of time(set by dump1090). You may have local loud signals that are causing issues. Does it happen when the local traffic is quiet?
Hi, thanks for your helpful response. I for some reason assumed that I had to be closed to an airport to have a signal strength issue which means i hadn’t considered that. I also hadn’t fully appreciated that a strong local signal could impact receiving tracks from aircraft further away.
Good question…i’ll take a look at a quiet time late tonight and post what I find.
Thanks again!
Would help to know your setup. You said you have a prostick plus, but do you have anything else between your antenna and the SDR? Is your SDR plugged directly into your RPi or do you have it separated with a USB cable? Are there any nearby EM/RF sources such as WiFi, a computer, a TV, monitor, etc.? Isolating your SDR as best you can will help a lot with this type of issue.
Related but different technology, I have a powerful directional TV antenna pointed in the direction (relative to me) of all the major TV stations in Kansas City. Yet I was still having issues getting clear, uninterrupted signals from my NBC and CBS stations (and you can just guess which two channels almost all Chiefs games are on!). I installed a 4G/5G filter and now everything is crystal clear.
Hi,
Thanks for your reply!
At the moment the prostick is plugged directly into a pi4, there is then an 8m run of LMR400 to the a 10 element colinear antenna mounted on a pole on the gable end of our house.
The property is rural, with very few neighbours. At the moment, other than the Wifi AP (about 5 m away), all appliances and devices are turned off in the property.
I must admit that I haven’t looked specifically for inteference at UHF at this site. I appreciate that its not directly related but I have never seen such low background noise at HF, as a result of the rural location. When I’m back at the site I’ll do some relevant testing.
I do have a prostick plus that I could swap out…would be interesting to see if the built in filter improves things.
When i’m back at that location in a few weeks I’ll test for RFI, put a gap between the prostick and the pi and try out the prostick plus and see where that gets me. If nothing obvious I might take a look at reducing gain.
The site, on the face of it, doesn’t perform too badly with around 700 messages per second for every 100 aircraft tracked although it does feel that it is underperforming in both range and count a bit given the location and antenna set up.
I’m sure i’ll get to the bottom of it. Thanks for the support guys.
Ha, just remembered that I have an SDR and fairly wideband discone antenna hooked up and accessible remotely…I’ll have a snoop around for strong signals.
The spectrum looks pretty quiet around 1090 at the site, but there does appear to be something going on ~100hz above. No idea if thats just slightly out of tune transonders or something else.
Edit: Ignore me, just read that bandwidth for 1090 is about 2Mhz
Just looked closely at the full bandwidth (and neighbouring areas) around 1090 and its quiet as a mouse. Possibly a very tiny bit of switched mode power supply interference, which could be solved by putting distance between the dongle and the pi.
Looking more closely, i’m seeing ADSB packets being received with an SNR of 25db+. These are strong signals…useful clue I think.
This is one of my systems in my bedroom(Mode S Beast and Uputronics Pre-amp). It is close to the TV. You can see the dropped in traffic when the TV is turned on(times are UTC and local time is UTC -5) .
A receiver with a wider dynamic range, like the airspy, may provide better reception. A simpler would be the pro-stick plus, as you have suggested, or even a simple filter.
Thanks Jon. I think the first thing I’ll try is swap the Pro Stick with a Plus and compare the difference. If no change, i’ll start to look into signal strength and gain.
That said, as mentioned before, all appliances are isolated from mains at this property other than the Wifi AP. At least while we’re not there.
So…an update!
It turns out that there is no issue at all.
When viewing the map by local IP all tracks are solid with barely any dashing, its only when viewing remotely using ADS-B Flight Tracking - FlightAware that the message rate is super low and tracks are patchy.
I was even able to bump up the gain a little today and range and positions have increased.
Thanks for your time everybody, turns out it was operator error after all.
I had wondered about this. I see the same differences between SkyAware Anywhere and from local IP. I guess I should have asked you where you were viewing from!
The good news is, anything you’ve done such as separate the RTL-SDR from the RPi, upgrade your SDR, or adjust gain settings, will help to improve your site’s future performance.
