Re: [Discuss-gnuradio] ham/amateur getting started

[David McQuate]

Broadcast radio & TV transmitters, police & fire repeaters, and others have 
potent signals.  If your system does not attenuate them, by using low-pass, 
high-pass, or band-pass filters, the peak voltage at your analog to digital 
converter may at times exceed "full scale".  The resulting non-linear response 
produces many spurious signals, that may mask the typically weak signals you 
are wanting to recieve.  An initial solution is to use broad-band attenuators 
to keep the total power reaching the ADC below full scale.  Then observe the 
spectral peaks and insert appropriate filters to knock them down.  The 
attenuation may then be reduced.  Frequently AM broadcasters are the worst.  A 
high-pass with cutoff around 1.6 MHz may be all you need.
Dave

Daniel Pocock <address@hidden> wrote:

>
>
>On 25/12/15 15:18, Ralph A. Schmid, dk5ras wrote:
>> Hi,
>> 
>> First of all, the USRP radios are kind of experimental radios, using
>them for real ham radio operation on antennas will require filters and
>PAs. "Out of the box" it will only be some proof of concept when you
>create a ham radio application with it. 
>> 
>
>Yes, that is why I was asking for more details about use with other
>equipment.
>
>> All 50 ohms, no limitations other than upper and lower border,
>regarding frequency. But connecting a roof-top antenna will most likely
>not work, due to the lack of preselection, you will receive lots of
>images and other garble.
>> 
>
>Can you give any practical examples of ways to deal with this, for
>example, choice of filters or antenna?
>
>Even with these limitations, are there use cases that you would
>consider
>viable?
>
>Regards,
>
>Daniel
>
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