Noise levels from a RTL dongle

Hi,I am new to Gnu radio but have it working on Mac OS X 10.8 and am
using a
E4000 tuner in a usb dongle. I have been experimenting with a Gqrx as
well
as GRC and am getting mixed results, with Gqrx I can get reasonable
quality
FM reception on 89.31 Mhz (radio 2 in the UK) with the wide band FM
(mono)
receiver and a 70Khz filter band. I have tried to replicate this in GRC
as
I want access to the demodulated signal as a live file (to be fed into a
std
unix pipe) for onward processing, however, the quality is significantly
worse than Gqrx. Can anyone help with my GRC graph.Details are on my
site,
Woodstercorp.com http://www.woodstercorp.com/sdrrtlfmreceiver.html
Any
help gratefully received.Alan

Replace the low pass filter with a band pass filter. The low pass
filter is not extracting the signal at the center frequency, but the
first 70KHz of the 1MHz bandwidth. Also, the decimation and
interpolation chosen in the resampler will destroy all information in
the channel. At the chosen values, the interpolation would be
essentially inventing the signal, rather than upsampling it.

Regards,

Mark McCarron

Date: Fri, 24 May 2013 15:40:39 -0700
From: [email protected]
To: [email protected]
Subject: [Discuss-gnuradio] Noise levels from a RTL dongle

Hi,

I am new to Gnu radio but have it working on Mac OS X 10.8 and am using
a E4000 tuner in a usb dongle. I have been experimenting with a Gqrx as
well as GRC and am getting mixed results, with Gqrx I can get reasonable
quality FM reception on 89.31 Mhz (radio 2 in the UK) with the wide band
FM (mono) receiver and a 70Khz filter band. I have tried to replicate
this in GRC as I want access to the demodulated signal as a live file
(to be fed into a std unix pipe) for onward processing, however, the
quality is significantly worse than Gqrx. Can anyone help with my GRC
graph.

Details are on my site, Woodstercorp.com

Any help gratefully received.

Alan

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