rtl_fm.exe issue or an I doing something wrong?

keenerd keenerd at gmail.com
Mon Oct 28 22:19:31 UTC 2013

On 10/28/13, Chris Hanson <lightningbolts at gmail.com> wrote:
> I am trying to listen to 424.175MHz and I'm using this:
> rtl_fm -p 30 -d 1 -N -o 4 -f 424.175M -s 16k -C|sox -r 16000 -t .raw -e
> signed-integer -b 16 -c 1 -V1 - -d

That looks correct.

> The issue is that I'm
> hearing another station 50KHz higher on 424.225Mhz in addition to the
> frequency I want.  So it looks as if it's not using a 16Khz filter.  Am I
> doing something wrong or is there an issue with rtl_fm.exe?  Thanks

It is a minor issue with rtl_fm.  The (very fast) downsample filter
tends to leak in places.  Soon this will be replaced with better

There is a better/slower filter that can be enabled with -F.  Check
your --help and confirm that -F is present and says 'hamming' in the


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