Re: Sample Rate & Hardware Considerations Tutorial: GNURadio.org

Barry,

I believe I know why the example sample rate was set that way in the past.

Many users use a RTL-SDR (RTL2832U chip with a R820T or E4000 tuner typically).
It works correctly over two groups of sample range: 225,001 -> 300,000 Hz and 900,00 -> 3,200,000 (or less).
If you choose a sample rate not in those ranges, the chip will "choose" a sample rate that it will work with and a message is sent to STDIO to inform the user.

So, you will see a lot of 250 KHz, 1 Msps and 2 Msps rate examples.

Thanks for updating the Tutorials!

Regards,
Ray Roberge
WACYB

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Message: 1
Date: Fri, 1 May 2020 12:24:49 -0500
From: Barry Duggan <barry@dcsmail.net>
To: james.hayek@gmail.com
Cc: Discuss Gnuradio <discuss-gnuradio@gnu.org>
Subject: Re: Sample Rate & Hardware Considerations Tutorial:
    GNURadio.org
Message-ID: <272447af-b0a4-048b-5a1c-a48e7ad93c18@dcsmail.net>
Content-Type: text/plain; charset=utf-8; format=flowed

James,

Thank you for your comments on our documentation! I started working on
the docs last year including adding flowgraphs to the block docs and
updating the tutorials to rel 3.8. The
https://wiki.gnuradio.org/index.php/Guided_Tutorial_Hardware_Considerations
is one which has been updated recently, but I didn't have the hardware
to test it. (I will next week).

So, for question 1: that tutorial was written several years ago. I don't
know why that sample rate was chosen, but some older computers have
trouble with high sample rates......

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