Buzzing but no AM signal

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Daniil
Posts: 2
Joined: Sat Feb 09, 2019 2:16 pm

Buzzing but no AM signal

Post by Daniil » Sat Feb 09, 2019 2:36 pm

Hello!

I'm trying to listen voice air band. I bought an RTL dongle, connect to it an antenna from old FM radio, and use an SDR#. SDR# installed as in instruction on site, drivers are installed successfully.
I can hear commercial FM stations, and audio track from UHF television channels, but when I try to listen air band (for example, 127.3MHz - ULLI (Pulkovo airport) ATIS, 10 kilometers from me) after I switching modulation to AM, I can see the signals, but can hear only buzzing. Same thing with 433 MHz diapazone - I can see the peaks of signal, but only buzzing are in headphones.

What's going on, how can I fix this? I can't even calibrate a dongle - I can't understand what station emits selected signal.
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jamesbond
Posts: 6
Joined: Sat Feb 09, 2019 2:10 am

Re: Buzzing but no AM signal

Post by jamesbond » Sun Feb 10, 2019 1:54 am

i find most of those spikes are interference from televisions or computer monitors, try leaving SDR running but turning your pc monitor off to see if there's a gap in the waterfall

rtlsdrblog
Site Admin
Posts: 1986
Joined: Mon Nov 19, 2012 11:54 pm

Re: Buzzing but no AM signal

Post by rtlsdrblog » Sun Feb 10, 2019 4:49 am

I'd recommend turning off RTL AGC first.

Those spikes are most likely noise from nearby electronics, those aren't actually airband signals.

If you haven't already, get your antenna outside, and with a good video towards the airport. That should help.

JEL
Posts: 116
Joined: Wed Feb 07, 2018 2:08 am

Re: Buzzing but no AM signal

Post by JEL » Sun Feb 10, 2019 6:33 am

Looks like noise to me too.

And your noise-floor at -30 dB seems very high, so a lot of the air-signals may be under that.

You should be able to get the noise-floor down to at least -60 dB.

Daniil
Posts: 2
Joined: Sat Feb 09, 2019 2:16 pm

Re: Buzzing but no AM signal

Post by Daniil » Sun Feb 17, 2019 9:13 am

Yes, that was noise from my secondary (old) monitor. I turned off monitor, use a good coaxial cable as antenna cable, and bring antenna far from PC to windowsill.
Now it's working fine. Thank you very much!

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