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

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 <daniel@pocock.pro> 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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