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Re: [Discuss-gnuradio] BasicRx Daugterboard Frequency Wrapping

From: Kelly Martin
Subject: Re: [Discuss-gnuradio] BasicRx Daugterboard Frequency Wrapping
Date: Thu, 22 May 2008 12:15:43 -0500

If your main use for this board is going to be broadcast FM, I would strongly urge you to use a fixed oscillator and a simple mixer to downconvert the received signal into a range that avoids alias.  The fact that FM broadcast band is split by a fold when used for direct conversion makes it a bit challenging for such a purpose; you're going to get alias images no matter how much filtering you do.  Since the FM broadcast band covers 87.9 to 107.9 MHz, you need an oscillator somewhere between 75.9 and 87.9 MHz to ensure that the entire downconverted band falls below the first aliasing fold point.  You would also want to use a bandpass filter so you don't end up with aircraft transmissions creating alias images. 

Or you could just use one of the other daughterboards. :)


On Thu, May 22, 2008 at 11:34 AM, isaacgerg <address@hidden> wrote:

It looks like i need to get an RF front end to pre-filter all that stuff out
of there.....
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