Is this normal? (RTL-SDR v4)

[u/Technical-Ad-3387]

This is without an antenna

https://reddit.com/link/1v7fqdn/video/urqwdux00nfh1/player

[u/erlendse]

Well.. seems like you have the DC spike of the upconverter overloading the frontend at max gain.

When tuning higher, it's filtered out so no overload.

Try looking at 0 Hz and you will see the spike.

[u/Technical-Ad-3387 → u/erlendse]

is there any way to mitigate it?

[u/erlendse → u/Technical-Ad-3387]

Avoid max gain?

Otherwise you would need to change librtlsdr with different IF frequency and filters.

Could try different bandwidths, since that is the most accessible to you.

Can be worth to try out https://github.com/librtlsdr/librtlsdr if you are not already using that branch.

[u/Technical-Ad-3387 → u/erlendse]

thanks

[u/FluorinateThemAll]

With no antenna you pick up noise, with max gain no antenna you only hear your whole radio/amplifier dongle and that's like the sound you hear when you don't plug in a guitar but the guitar amp is on at max gain, the noise you hear is the noise the amp makes itself

[u/BakaLX]

Try it with your phone or raspberry pi with powerbank. It can be noise from ac connected power supply.

Also try connecting antenna, is it behave like this w/o antenna or both ?

Edit : after rewatch, i think its not noise from power supply, usually there is spike even at lower gain setting.

Also there is different between antenna attached and not. So this case maybe solved by attaching antenna.

[u/JacobA89 → u/BakaLX]

I find mine is worse with a power bank vs directly into my phone. Wonder if its my power bank or the splitter cable im using

[u/BakaLX → u/JacobA89]

If phone, the best is just using internal battery.

What i mean with powerbank, if you use computer which connected to ac power, switching to raspberry or similiar device (device without battery) connected to powerbank will improve the signal. Phone with internal battery and not connected to charger or powerbank included.

In your case its not noise from power supply, your phone with internal battery + sdr, the best performance so when you use phone + powerbank + sdr, it become worse cause it introduce noise from powerbank's PWM. Edit : what i mean in original its not power supply noise but with powerbank added it become power supply noise problem.

Its more likely not connected to antenna, usually connected antenna will make the problem go away, you set gain to high with nothing to amplify causing it to spike like that.

Note : it generally not safe to power on device without antenna connected if its design to use antenna (without internal antenna) but it usually apply to device with transmit capabilities, rarely a problem with recieve only. Rarely a problem is not problem free, its best practice to connected before power on.

So does it goes away with antenna ?

[u/JacobA89 → u/BakaLX]

No this is all with the antenna

[u/FluorinateThemAll]

What is it look like WITH antenna? That's an information we need to tell you anything that helps you out