Re: [Discuss-gnuradio] URSP/Gnuradio for amateur radio usage

[rafael2k]

Thanks Johnathan,
I'll try to get such amplifier and probably a passband filter.
I send the schematics to the list If I get something working.

There are others SDR radios out there that were made for amateurs, like 
Flex5000, softrock and others, but they all use a stereo sound cable 
connected to the PC soundcard as interface (at most 96kHZ and 20kHz 
bandwidth), ..., ursp is much more powerfull.


bye,
Rafael Diniz

Em Monday 27 October 2008, Johnathan Corgan escreveu:
> On Sun, Oct 26, 2008 at 9:08 PM, rafael2k <address@hidden> wrote:
> > I'd like to know the output power I can get from a usrp 1, and if someone
> > has any experience with this kind of experiment, like what amplifiers to
> > use, what filters, and things like that.
>
> The maximum USRP1 output using the LFTX board is approximately 2V P-P
> into 50 ohms, or about 10 milliwatts rms.  Depending on your waveform
> peak to average ratio, your rms power will be less.
>
> On TX, to get to say, a max of 5W for QRP operation, you'd need a PA
> with at least 27 dB of gain.  For operation with SSB, this would have
> to be a linear amplifier.  For CW only, you could use a non-linear PA
> which would be easier to design.
>
> The LFRX board has no gain, and essentially just provides
> anti-aliasing filtering and impedance matching between the input at 50
> ohms and the analog-to-digital converter input circuitry.  You can
> think of it as having roughly a 55dB noise figure, so you'd need at
> least that much external low-noise amplification to get any sort of
> useful weak signal reception.    (The 55dB figure was from an
> empirical measurement with a signal generator; YMMV.)
>
> Since the ADC is digitizing the entire 0-30 MHz spectrum, it would be
> essential to have a band filter ahead of the amplification, in order
> to avoid strong out-of-band signals limiting the amount of gain you
> could use.  In addition, you'd want some sort of analog AGC.
>
> Anyway, it's obvious the LFRX and LFTX were designed as baseband
> interface cards, not as an HF receiver or transceiver.  Still let us
> know what you come up with.  It's certainly possible, given the open
> design of the USRP1/USRP2, that you or someone else could design
> customer daughterboards that incorporate some or all of the above.
>
> -Johnathan (AE6HO)



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