Odd behavior: Picking up radio station at wrong frequency

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Mike_K
Posts: 3
Joined: Thu Jun 24, 2021 2:48 am

Odd behavior: Picking up radio station at wrong frequency

#1

Unread post by Mike_K »

Hi all,

I'm a new player and just getting started, so I'm sure just like the rest of you when I had my system set up I tried to listen to some FM radio stations.

I'm in the US so I tried looking for stations in the 87.8 to 108.0 MHz range but couldn't find anything. I looked around and long story short I'm finding the stations at much lower frequencies, around ~45 MHz. Why would that be?

I'm using the NEW GEN. RTL2832 dongle with a standard antenna (https://www.ebay.com/itm/402855279936?var=673092915770). For software I'm using the CubicSDR software.

If it's important, the antenna is about 12 cm long.

Thanks in advance for any help
Mike

G4ZFQ
Posts: 58
Joined: Wed Aug 19, 2020 10:26 am
Location: Cowes Isle of Wight

Re: Odd behavior: Picking up radio station at wrong frequency

#2

Unread post by G4ZFQ »

Mike,
It's my guess that it is some mis-configuration in the software.
This group is actually in support of SDR-Console software https://www.sdr-radio.com/ if you were using that then a good reply is guaranteed.
Otherwise you may get someone who knows..
Or, maybe the CubicSDR software group, I assume there is one?
Alan

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

Re: Odd behavior: Picking up radio station at wrong frequency

#3

Unread post by jdow »

Keep dongle gain low. About 20 dB is sufficient to set a decent noise figure and dynamic range. If you gain is set really high (using RTL's AGC?) you can get more problems than usual. It's an RTLSDR dongle. It's cheap. Don't expect extremes of good behavior. It is a good tool for getting your feet wet.

{^_^}

Mike_K
Posts: 3
Joined: Thu Jun 24, 2021 2:48 am

Re: Odd behavior: Picking up radio station at wrong frequency

#4

Unread post by Mike_K »

Thanks you both for your replies!

My main and only reason for using CubicSDR is because it was the first option I saw that would work on my Macbook straight away. I will look into getting
sdr-radio working as well.

And regarding the quality of the dongle: sure, I'm not expecting it to be great, although the audio quality I get for the stations seem to be really well, they're just shifted by ~100Mhz (-:

I did find an option in CubicSDR to apply a frequency shift, and I think this might the way to go. It doesn't seem to shift the frequency perfectly,
but at least it gets me closer. Now I have to find and listen to a station until I can identify which station it is (and thus it's actual frequency)
and then I apply smaller shifts to creep closer to the actual frequency. I still expect I might have some setting incorrect since a 100MHz shift
seems like more than what can attributed to calibration errors of the dongle or anything like that.

Cheers
Mike

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

Re: Odd behavior: Picking up radio station at wrong frequency

#5

Unread post by jdow »

Before you run away with this 100 MHz shift - what happens when you tune to known FM station frequencies? You should receive them very much the same quality or better than a commercial FM receiver on the same antenna. I would not expect the error to be even as large as 100 kHz let alone 100 MHz. For a 100 MHz error either your software is malconfigured (find CubicSDRs discussion group and ask them as this is the SDR Console group) or something really dramatic and goofy is going on inside your dongle.

I doubt you'll get SDRC running on your Mac without a Windows install. SDRSharp is another SDR that may be worth your exploration.

{^_^}

Mike_K
Posts: 3
Joined: Thu Jun 24, 2021 2:48 am

Re: Odd behavior: Picking up radio station at wrong frequency

#6

Unread post by Mike_K »

Final update:

I decided to buy the authentic RTL-SDR aluminium dongle, and it works perfectly and as expected, so I believe the other dongle was faulty.

I got the message that this forum is for the SDR-Radio software, but I though I'd post this final update since in the end the problem was not
software-related and this thread might maybe help someone out in the future.

Cheers!
Mike

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