Help! Signals Drop Out Intermittently

Help! If someone is really bored or has a second monitor that can be left on in the corner of the room, you can view my feed at http://airplanes.ddns.net. If you view it for long enough, especially during peak hours (I am UTC-4, EDT) you’ll see the problem described below.

I am new to ADS-B tracking. Had my setup running for about a month now. From day one, I have been fighting a problem I can’t solve. I live 1.5 miles from Fort Lauderdale Int’l and 25 miles from Miami Int’l. During peak hours there are 150 planes on my map and 500+ signals a second received. If I look at the age of the signal (right hand column in dump1090 display) if is usually 0 or 1 with the exception of distant planes barely in range.

Numerous times a day, I stop receiving signals for anywhere from 10-90 seconds. The age of the majority of my signals will be 0 and then starts counting up until they either reset to zero or disappear off the map. During this time, the messages received drops by 80%. Then a minute later they all come back all at once. Sometimes they stay for an hour, other times they start to disappear a minute later. Completely unpredictable. When I view the blue block graph showing my stats, it looks like a mosaic of light and dark speckled tiles. Most other people in the area seem to have a line of blue which fades in and out consistently on a daily basis.

The problem is not contingent on temperature, wind or rain. Happens with all weather conditions.

Happens on both WiFi and a cabled network connections.

Here’s what I have done thus far…

Swapped antennas. Same problem with homemade cantenna or purchased FA antenna.

Swapped all coax. Currently have brand new 50’ run of LMR400 with professionally installed connectors. Also swapped the SMA pigtail that connects to the receiver.

Took the receiver out of the blue case, thinking it might be overheating inside.

Put receiver back in case and wrapped with foil, thinking the foil might block some unknown source of RFI.

Swapped receivers. Have a blue FA ProStick Plus. Swapped with a friends known good unit. Same problem.

Tried numerous high quality power supplies and USB cables to power my RPi 3.

Switched to a powered USB hub to power the receiver.

Reimaged a new image on a new SD card.

Put a cooling fan blowing on the Pi and receiver.

I have just started fiddling with the gain settings. I am seeing a lot more planes by manually adjusting gain instead of leaving it at -10, but the problem of signals dropping out still remains.

In summary, I have physically replaced every piece of hardware with the exception of the Pi itself. I really don’t think the Pi is the problem. When my setup is acting up, I can still SSH into the Pi and snoop around.

I am pulling my hair out and open to ideas to try. Please help!

Jason

I may have stumbled across my problem. Can’t believe I didn’t make this connection sooner. I am a ham radio operator and have a small repeater setup at my home which transmits 5w on 440 MHz. When the repeater keys up, the ADS-B receiver drops out. I am going to start another thread asking for help from other ham operators…

Jason

Are you using a FlightAware 1090 MHz filter in your setup?

I found that I needed one even when using the Pro Stick Plus.

See PM.

Chris, I received your PM and tried to reply, but the message is stuck in my outbox. I don’t think it sent and will not show up in my Sent Items. I’ll have to figure that you later. Thanks for the offer! Using the blue FA Pro Stick Plus. The filter is relatively cheap, so I think I am going to take a chance and order one…

Jason

Just a quick note to mark this problem solved for anyone who stumbles across it in the future. Added an external FA filter to my blue FA Pro Stick Plus, and the drop outs went away. RFI from a nearby UHF transmitter was drowning out my received signals.

Jason

When I key up on my ham radio, I have the same issues.

Took me a bit to figure my issue out as well. I went to reply to this, and see you already figured it out :slight_smile:

Take care,
73

WX9RLT

Wow, your range has increased significantly.
You already have more position reports than last Sunday and there are still 7.5 hours until the end of he UTC/GMT day.
You may want to consider a metal case for the RPI and Dongle to further reduce interference.
Optimizing gain may also help if you have other sources of noise.

Consider adding dump978, if you are interested in GA aircraft.

I was thinking it was receiver overload but thought it might be further from you.

BTW, do you have a webpage describing your repeater? Just got my license and learning about this stuff.