Re: [Discuss-gnuradio] What impedance are the wires and antenna?

On Tue, Jul 28, 2009 at 05:02:42PM -0400, Jonathan Coveney wrote:
> I will try and get a hold of the TVRX board, but in the meantime, are there
> any workarounds?

Use an FM dipole antenna, or for that matter, just plug a 75cm 
(1/4 * 3e8/100e6) wire (not coax) into the center of the SMA connector
and tape it to the wall.

> Is this because the BasicRX doesn't have a filter and
> whatnot in it to specifically target the radio frequencies?

Yes.  Read up on "bandpass sampling" for the details.

Eric


> 2009/7/28 Eric Blossom <eb@xxxxxxxxxx>
> 
> > On Tue, Jul 28, 2009 at 03:55:26PM -0400, Jonathan Coveney wrote:
> > > And I am using the Basic RX, if that makes a difference.
> >
> > It will work more-or-less, but it's not really the daughterboard to
> > use to receive broadcast FM.  The TVRX is a much better choice.
> >
> > The USRP1 samples at 64MHz, which means that when using the Basic Rx
> > to attempt to receive the broadcast FM band, you'll be "bandpass
> > sampling" and there'll be a fold at 96MHz (3/2 fs), right in the
> > middle of the broadcast FM band.  You won't be able to separate out
> > 96M-f from 96M+f for any frequency offset f.
> >
> > Eric


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