RTL-SDR v3 / LNA

LOL no all got willys

● dump1090-fa.service - dump1090 ADS-B receiver (FlightAware customization)
Loaded: loaded (/lib/systemd/system/dump1090-fa.service; enabled; vendor preset: enabled)
Active: active (running) since Wed 2019-11-27 18:29:53 GMT; 3min 23s ago
Docs: https://flightaware.com/adsb/piaware/
Main PID: 1092 (dump1090-fa)
Tasks: 3 (limit: 2200)
Memory: 5.1M
CGroup: /system.slice/dump1090-fa.service
└─1092 /usr/bin/dump1090-fa --device-index 0 --gain -10 --ppm 0 --net-bo-port 30005 --max-range

My commands
sudo piaware-config rtlsdr-gain 20.7
Set rtlsdr-gain to 20.7 in /etc/piaware.conf:9
pi@raspberrypi:~/rtl_biast/build/src $ sudo service dump1090-fa stop && cd ~/rtl _biast/build/src && ./rtl_biast -b 1 && sudo service dump1090-fa start

So you are doing it wrong. Seems you are not on a piaware image.
For Beginners - How to Set / Change Gain

So you didn’t change anything. Read the link, the procedure is different depending on what install you have.

Ahh yes raspberry buster with piaware over top

Yes i know where ive gone wrong
thankyou all

Ahhhhh Bisto…
i even forgot to reapply filter/amp whilst adjusting tests jeez all working well now
fantastic help all

If you read RTL-SDR’s site:

In addition please remember that this is a high gain LNA. It is expected to be used at the antenna side, with some 3+ db loss expected on the coax. However, if desired, it can still be used on the receiver side. If used on the receiver side or with a low loss run of coax, you will need to tune the RF gain on the RTL-SDR dongle. By default most software sets the RF gain to maximum. We recommend turning the RTL-SDR RF gain down to about 32 dB if connecting it directly to the dongle, otherwise the high input power may overload the dongle causing poor performance.

Personally, I found 8dB attenuation between the amp and dongle to be about right.

For me this triple filtered amp did not work as expected.

I had a working station built with a FA Orange Stick (amp only, no filter) + FA Filter (LC-type, not a saw filter) working fine on the antenna foot (2meters of cable) and wanted to move the Raspberry + Dongle down from the attic.

Using the RTL-SDR amp I had a sensible loss of messages/airplanes. When I increase the gain strong sinals were saturated. If I decrease the gain I lose range (and messages as well).

That was a no go for me, kept the rasp on the attic and tried to shield everything agaist ESD (my original source of problem).

I live near a dozen of FM towers, nothing works here without filters, event VHF radios requires filters to work.

Regards.

What gain range were you using and what kind of cable did you use?

There is always the possibility that you got a defective unit.
A scan with both units would be interesting and might tell you if the LNA is defective: Do I Need A Filter?

Also please check if you bought the filtered or unfiltered LNA from rtl-sdr blog.
The unfiltered version will obviously not be as good. You could always try the FA filter you have in front of the LNA.

Tried many gains, 28, 32, tried even a python script that changes the gain a collect messages available on this forum. I have collected running to hold statistics

I’m using a RGC58 cable and in the past (before an ESD strike) I was using a SAW filter + a cheap LNA from Aliexpress with very good results (the same if not better than the FA Stick directly on the antenna), but was unable to reproduce these results using this LNA.

I bought the ADSB version (not the unfiltered wideband) directly from the RTL-SDR Blog Store.

Very much sounds like a bad unit.
If you can manage a spectrum scan with the bias-t switched on and send that picture to the sales team at rtl-sdr blog, i’m sure they’ll ship you a replacement unit.

What cable length do you have?
RGC58 is available in both 50 and 75Ohm versions - which do you have?
While it’s good quality cable, it’s far from ideal at microwave frequencies.

Around 26 meters of 50ohms. Manufacturer datasheet is pretty close to this RFS cable too, I would estimate a 10dB loss. Again, this very same setup worked well using a cheap Chinese amp, but they don’t have ESD protection and burn easily

With 26M of RG58, there is next to no 1090Mhz signal going to be reaching your dongle. While rg58 is an acceptable cable for VHF frequencies, it has very high losses for higher frequencies.

??

My cable is RGC58, almost half the loss of a standard RG58. According to its datasheet it has a 33dB/100m loss @ 900Mhz, so I suppose it has around 10dB loss for 25meters @ 1090.

The RTL-SDR has a final 27dB gain, enough to cope with the cable loss. In fact the signal is so strong it saturates the FA Dongle. I have to use a standard non-amplified dongle with lower gain to achieve good results, yet lower than using the FA dongle + Filter directly on the antenna.

I dont believe the AMP is defective as it works as expected, but there is something not perfectly matched to handle such strong interferences in my place.

Again, I live in the FM/TV Antennas’ mountain of my city, I have somewhat around 20 stations of > 60kW in a radius of 2km. I cant use my Yaesu airband receiver without filter, it’s full of noise and saturates. Not sure if the RTL-SDR was made with such conditions in mind

I am not a technical expert in signals, but how should it work if the loss of signals goes to zero? I assume the LNA needs at least some traces of signal to amplify it, or?

It handles strong interference very well, that’s why i asked you to record the spectrum.

Use it in place of your current dongle after all that loss and the filter for all i care.
It should still outperform the standard dongle.

Also if it’s worse than some random amplifier you tried, it’s definitely defective.
Anyhow if you don’t want to check the spectrum because you are certain it’s not defective, be my guest.

I had to buy three units from Amazon before finding one that worked…