Hello people,
I’m aiming to transmitt in some amateur radio bands, especially the 40m
band.
The bands that LFRX and LFTX can cover are (considering the 30MHz
lowpass
filter):
1.8, 3.5, 5, 7, 10.1, 14, 21, 24.89, 28 MHz
I know gnuradio can do SSB and CW modulation 
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.
Thanks,
Rafael D.
On Sun, Oct 26, 2008 at 9:08 PM, rafael2k [email protected] 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)
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 D.
Em Monday 27 October 2008, Johnathan C. escreveu:
On Mon, Oct 27, 2008 at 8:36 PM, rafael2k [email protected] wrote:
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.
There are exceptions to your “they all use a stereo sound cable” rule.
One that you might want to look at is here http://hpsdr.org/ There
are several sub projects within HPSDR. Look at both of these:
http://hpsdr.org/mercury.html
http://hpsdr.org/penelope.html
Chris Albertson
Redondo Beach, California
thats true Chris,
Thanks for the information.
but none runs gnuradio, usually PowerSDR is used.
bye,
rafael diniz
Em Monday 27 October 2008, Chris Albertson escreveu:
The transmitter is being designed now…
From the QS1R Yahoo group:
“The SRL QS1R features expandability with an I2C and SPI/Microwire
expansion
bus. Also planned is a PCI interface version of the QS1R with
accompanying
DAC/transmitter board as well as various VHF/UHF/Microwave add-on
boards.”
On Wed, Oct 29, 2008 at 6:23 PM, Robert T. [email protected]
wrote:
And do not forget the new QS1
I guess it’s helpful to see some validation of USRP2 pricing. 
(It
looks like a RX only USRP2 plus USB2.0 bottleneck, minus external
refclock)
An RX only device doesn’t meet Rafael’s interest though: Anyone
working on a GNU Radio driver for this thing?
Nice gadget, but prices are insane.
cheerio Berndt
That one is nice. but the price is not that good, and the software runs
on
Windows… (of course we could write the driver to gnuradio).
btw, back to our ursp/gnuradio, a friend that works w/ RF will try to
design a
board that conects to the LFTX w/ the stuff needed to transmit SSB and
so on.
If I get something, I email to the list.
I already transmitted from gnuradio to a 2m amateur radio without any
add-on,
just the standard BasicTX.
bye,
rafael diniz
Em Wednesday 29 October 2008, Robert T. escreveu:
The code is open source and being ported to Linux. Integration with GNU
Radio is being planned.
Hi Tiller,
Wow, very nice to hear that!!!
Is there any code of this port already available?
bye,
rafael diniz
Em Friday 31 October 2008, Robert T. escreveu:
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