FlightAware Discussions

Testing Signal Quality with Spectrum Analyzer?


#1

Hi guys,

Little green here and just wanting to know how to test the signal quality and any interfering signals using a Pro Stick to Pro Stick Plus. Also understanding how to set the gain to ensure maximum signal quality.

Is this possible I have seen software like SDR# and HDR etc.

Thanks in advance and sorry if this has been asked in the past.


#2

Have a look at this post:


#3

RTLPan or Spektrum are both much easier to get up and running.

Your ProStick Plus has a band-pass filter built in (otherwise the same), so should attenuate out-of-band signals.
Use the ProStick to get a better idea of what is around.


#4

You still get a good idea of the 800 and 900 MHz bands. It is attenuated for sure but the various mobile frequencies are so strong that a single SAW filter is fighting a losing battle :wink:

I’ve been wanting to run a comparison between
ProStick Plus combined with FA filter
vs
rtl-sdr blog LNA + rtl v3 dongle

And check what the spectrums look like at the gain i use to get around -10 dBFS average signal level for ADS-B messages.


#5

This is my scan at a gain of 38.6
Current git version of rtl_power from (https://github.com/keenerd/rtl-sdr.git)
Command line:
./rtl_power -f 700M:1200M:100k -e 30m -i 30 -c 50% -g 38.6 -F 9
(the dongle is using 1.6 GHz as a sample rate, with older versions it will use 2.8GHz sample rate)

I know it’s a bit higher gain than normal for these scans but for comparability i wanted to use the same setting i used for receiving with the same antenna (spider on the top of the roof)

Pro Stick Plus without filter (except internal) and then with the FA filter compared:

You can see the 810 MHz is practically eliminated by the FA filter but the band around 940 MHz is not reduced enough, though it is reduced.


#6

Completed the comparison:
1: ProStick Plus without external filter
2: ProStick Plus with added FA filter
3: RTL-SDR BLOG V.3. with RTL-SDR BLOG LNA

The weaker signal at 1090 MHz for the ProStick Plus is not a shortcoming of that dongle, just different gain.
But even with higher gain at 1090 MHz the LNA combination shows its strength at eliminating virtually all out of band noise!


Sudden Loss of range
#7

Fantastic comparison above.

I have both FlightFeeder, Pro Stick and Pro Stick Plus and filters if required so will experiment.

I had issues configuring SDR# when I tried but hopefully with all your assistance I will be able to get it scanning and I can start eliminating interfering frequencies.

Appreciate it guys thanks


#8

The RTL-SDR BLOG Lna seems to work pretty well.

I had a spare v3 dongle so I ordered one, not expecting much, but it actually improved reception further away and in less favourable directions ( wall, hills).

Message rate overall is higher, too, compared to a Pro Stick Plus + a sysmocom cavity filter. Got rid of two adapters, too, maybe that helps a bit as well.


#9

Has anyone got a pre built Raspberry Pi image that is used for Spectrum Analysing.

My computer doesn’t seem to like the USB drivers used by Rtl# etc

Might just build one using raspberry pi instead


#10

No. What is the problem with the instructions linked in post #2 of this thread?
Talking about the OPTION 1 for the raspberry pi?
It’s quite detailed.