Distortion in Audio When using BC-FM Mode - SOLVED

4X1RV
Posts: 22
Joined: Sat Aug 08, 2020 6:39 am

Re: Distortion in Audio When using BC-FM Mode

#11

Unread post by 4X1RV »

Hi
Why is the noise reduction selected (it will introduce distortion...)

AussieLand
Posts: 16
Joined: Thu Nov 03, 2022 8:13 am

Re: Distortion in Audio When using BC-FM Mode

#12

Unread post by AussieLand »

OK. I have switched off the noise reduction, but it has made no noticeable difference.

The noise no longer exists since I lowered the sample rate to 2.5Mhz

Thanks.
John. VK4JRH

AussieLand
Posts: 16
Joined: Thu Nov 03, 2022 8:13 am

Re: Distortion in Audio When using BC-FM Mode

#13

Unread post by AussieLand »

I've switched on RDS, but it looks like the signal is not strong enough, as I'm geting patchy text which is mostly unintelligible.
John. VK4JRH

jdow
Posts: 800
Joined: Mon Aug 10, 2020 8:17 pm

Re: Distortion in Audio When using BC-FM Mode

#14

Unread post by jdow »

AussieLand wrote: Sat Nov 05, 2022 11:22 am
Simon G4ELI wrote: Sat Nov 05, 2022 6:06 am Hi John,

Depending on the dongle 2.5 MHz is just too much. get a decent antenna and you'll see the RDS text. I also suggest zooming to the max to see more stations.
Hi Simon,
I tried a lower frequency, but I found that I couldn't get the span in the spectrum section, it was cut on the ends. It seems happy at 2.5 Mhz.
Seriously you want to run at 2.4 msps. At 2.5 Msps you will hear a persistent ticking. That is dropped packets on the USB interface. This is a limitation for nearly all rtlsdr type dongles. Once, just once, I found a dongle with a sweet spot above 2.4 Msps that worked but none of the other values I tried between the one that worked and what I found produced good results.

If bandwidth is more important than fidelity go for it. If good listening experience is more important 2.4 Msps is your best friend with rtlsdr dongles. Run them there even if you don't need the bandwidth. It gives you a LITTLE better dynamic range between overload and clean signal. (A small single digit number of dB is not something to toss away at random, of course. And 8 bits per sample is a low dynamic range device.

{^_^} (Owns about 10 of the infernal little things. I've outgrown them. If you need the bandwidth and the SDR experience interests you the AirSpy R2 is a very nice tool for VHF.)

AussieLand
Posts: 16
Joined: Thu Nov 03, 2022 8:13 am

Re: Distortion in Audio When using BC-FM Mode - SOLVED

#15

Unread post by AussieLand »

Thanks for that Joanne. I have set the sampling to 2.4 MSPS.
John. VK4JRH

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