FM – DAB+: my logblog!

The other day I bought a Low Noise Amplifier from Amazon UK.
The device is designed by RTL-SDR.com.
Inspired by Nils Schiffhauer’s review of Qirx 3.1.2 Beta (part 1 and part 2) it was time to check out the RTL-SDR + LNA + Qirx 3.1.2 Beta combo.
Data was always gathered in the same time span and with the same antennas.

Reception conditions were flat during these observations, no lift at all.
‘Without LNA’ doesn’t mean switched off but physically disconnected.

With nesdrSMArtee the same results are obtained. However the BIAS TEE cannot be switched off when using nesdrSMArtee!

Click on the pictures below to enlarge them.

Wideband LNA purchased from Amazon.

My set-up: coaxial lead to the Emme Esse stacked antennas is about 20 metres in length.

SNR (db) readings in Qirx are virtually equal when using a LNA or not. There’s certainly no deterioration in signal quality when using this LNA.

With the LNA hooked up to the RTL-SDR Qirx’s AGC does a great job and the Gain (db) drops considerably.
You can switch off the AGC and go for manual Gain settings, but there’s no need to do so: Qirx’s AGC works just fine.

The LNA performs very well when considering Strength in Qirx. Strength is represented on a scale from 0 to 1.
Nearby strong transmitters at my QTH like Veltem, Liège or Wavre are of the same ‘Strength’ with or without the LNA.
However more distant transmitters showing up in the TII are a different matter and spectacular improvements can be seen.

Measuring the ‘Magnitude‘ also clearly shows the impact of the LNA.

Conclusion

Do you need this LNA next to your RTL-SDR when doing some serious DAB listening?
It all starts with a good rotatable antenna with a clear view and positioned as high as possible and not too long a coax lead. That’s of course almost impossible, so one needs to find a satisfying compromise.
When there’s no lift or ‘conditions’ at my QTH there’s not much of a difference when using a LNA. No muxes are found which could not be heard under normal conditions, although signal strength has definitely and considerably improved.

What will happen when there’s a great opening like e.g. on December 29 2019?
We’ll have to wait and see…

To be continued.

Update April 17 2021.

A quick indoors test: a laptop with a short whip. QIRX and RTL-SDR with or without LNA.
Without the LNA 4 muxes can be received. With the LNA 5 are captured.
The test was done several times and always the same results were obtained.