FlightAware Discussions

Upgraded to RTL-SDR USB and LNA power by raspberry pi

I recently upgraded from FlightAware 1090 MHz ADS-B Bandpass SMA Filter > FlightAware Pro Stick Plus to RTL-SDR Blog ADS-B Triple Filtered LNA > RTL-SDR BLOG V3 R820T2E

I’m currently using a Rapsberry pi2. Using a multi-meter, the output from the V3 dongle is approx 4.7v and i see the green light visible when connected on the LNA.

Upgraded on/around 10th and was playing with the settings for next 2 days image
Is this any good?

Coverage is:
I’m based fairly close to London Heathrow and live in a Flat with antenna mounted internally on window facing north, hence lack of south coverage.

Is the raspberry pi sufficient enough to power the LNA or will i require an external power source to it?

That’s fine.

Seems you only tried the extremes in gain :slight_smile:

Typical gain i’d recommend for that combination 23, 25 or 28 … somewhere around that.

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I have same LNA with Flightware Pro Stick and pretty low feeder loss. I power the LNA via a Bias Tee and ended up putting 16dB of fixed attenuation between the Dongle and the Bias Tee to get decent dynamic range (i.e. not overloading the Dongle with signals from nearby aircraft). Then played with the Dongle gain over time.

For reference here’s my version of the same graph

Correct, i only got down to 32ish, will try testing further today.

I did further research and due to using a LNA i dropped the gain completely and slowly work from there to see what worked best. The sweet sport being between -24 and -28.

I decided to start from scratch and install fresh image or raspi os and switched to dump1090-fa (previously using mutability).
I also noticed i was getting a lot more under-voltage detected on the raspberry pi so I’ve changed the cable and so far looking good.

From the fresh install I’ve noticed graphs1090 is capturing noise levels too.

That’s starting to look better with much increased dynamic range between peak signal and weakest signal (although the most recent few minutes are not so good).

Could probably still benefit from some attenuation between the LNA and the dongle. How long is that feeder and do you have some extra cable you can try putting inline ? - I’d doesn’t have to be low loss cable !

I would hope your message counts have gone up as a consequence of the changes made.

Not using an amplified SDR but rather the rtl-sdr v3.
Reducing the gain is all that’s necessary.

Reducing the gain further can often reduce range while increasing message count and improving close by low flying aircraft reception.
That’s a tradeoff everyone has to make for themselves.

Sacrificing approx 25db resulted in approx 20 mile loss from max range.

I’m currently using a raspberry pi2, 30cm usb extention to USB dongle which is plugged straight into LNA and then 2 or 3 meter cable (still rolled up as pi sits beneath the antenna on the window sill) to a 10 element antenna. As i live in a Flat, the antenna is held internally on the window using fish tank suction cups.

I’m currently feeding FA, FR24, ADSBExchange and RadarBox.

If your interested i’ll leave my stats page link here: John Rambo ADS-B Feeder Statistics - FlightAware

I’m going to let it run a few days before i try any further improvements.