Hello to the Forum, by connecting a Nooelec LaNA - Wideband Ultra Low-Noise Amplifier
, I wanted to improve the range and performance of my ADS-B receiver. Unfortunately, when the Nooelec LaNA - Wideband Ultra Low-Noise Amplifier is connected upstream, there is no longer any signal in the FlightAware SDR stick and therefore no longer in the Raspberry Pi. The interposition of a Nooelec SMA DC block between Nooelec LaNA - Wideband Ultra Low-Noise Amplifier and FlightAware Stick did not produce a positive result either. Please could you have a look on it and someone explain to me what I’m doing wrong?
My configuration: FlightAware Stick, Raspberry Pi 4, 1090MHz ADS-B collinear antenna (1.5m)
Using an LNA without a filter is often a bad idea, interference can overload the following LNA as the FA sticks have one on the input.
The FA filter would be cheaper than a DC block and more useful.
Looking at the Nooelec data I think your preamp will be applying DC voltage from its USB power straight into the Prostick.
You should have your DC block between the preamp and the prostick.
However I suspect the biggest problem is that you are just overloading the prostick with lots of large out of band signals. A wideband preamp is not what you want.
When I reconnect the antenna cable without LNA, everything works fine again, so I think that it is not connected to the center pin. As you can see in the pictures, I connected the so-called output next to the power led to the input of the FA-Stick and connected the antenna cable to the connector labeled input next to the USB connector.
I have a similar test setup that works very well. It matches the performance of a 1090 MHz LNA. The connection sequence is:
FA Antenna → 7m LMR200 → FA 1090 MHz blue filter → Nooelec LaNA (powered by USB wall wart) → DC block → FA Pro Stick Plus → RPi 4
I’m not sure if a RPi can provide adequate USB power to the LNA because it is also powering the ADS-B dongle, etc. I also tried putting the filter after the LNA but then the LNA also amplified the severe interference at my location thus providing poorer results.
LNA are typically 50 mA or less, just the rtl-sdr is 150 mA.
500 mA extra draw aren’t any issue for the pi, 150 mA certainly isn’t.
Well you connected it using the DC block or some sort of coupler.
The DC block has to have a pin on each side then.
You’re not filtering anything, could be that interference is competely overloading the LNA of the FA prostick meaning no reception at all.
Even with only the prostick you have a low message rate which could mean interference.
Showing the signal graph from graphs1090 would be helpful.
Also it’s very likely you’d need to significantly reduce the gain … to something like 25 or lower.
I should have enumerated the etc. The RPi 4 is also connects to a fan, keyboard, mouse, 20" display, spectrum analyzer dongle and a printer. External power for the LNA reduces the overall power load on the barely adequate RPi 4 3½ amp power supply. Most of the issues I’ve encountered are power related. I agree that a bare bones RPi 4 can handle an LNA and an ADS-B dongle.
The problem shouldn’t be the power supply of the LNA, this is an extra USB power supply.
At first I only connected the LNA to the SDR stick with an adapter, on the second attempt via a DC blocker but both times were unsuccessful. Where can I find/extract the signal graph? I don’t have any frequency meters. I also don’t know how and where to reduce the gain. I ask for further information.
best regards
