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

From: Markus Heller
Subject: Re: [Discuss-gnuradio] ham/amateur getting started
Date: Fri, 25 Dec 2015 22:02:47 +0100


yes, what Ralph said is very true. The real strength of the USRP series
is it's high sampling speed. I own the USRP2, which is already around 5
years old and already did 100 MS per second, but it was rather expensive
at that time. 

You can get much cheaper SDR hardware today such as the RedPitaya, or if
you just want to do receiving experiments, the RTLSDR USB stick is
probably unbeatable in terms of function vs price ratio. 

You get 3,2 MSPS for 10 Euros. 

Remember the Nyquist Theorem, which tells us that you can sample 1,6 MHz
wir 3,2 MSPS, and common amateur radio signals are generally far smaller
than 1,6 MHz. So the RTLSDR stick will probably be sufficient for most
of your experiments. 

The USRP series is the upper end compared to the RTLSDR device. It
offers unimaginable possibilities in terms of sampling, and it can
generate signals just the same way. And the recent USRPs can produce any
arbitrary signal up to 6 GHz. 

If you want to make real use of it, please still do consider to care for
efficient preselection, as the ADC will swallow a huge bandwidth and
consume all the energy that's out there. And it may turn out to rather
unsensitive if you have a strong transmitter somewhere in the spectrum. 

For this reason, a good understanding of classical RF engineering will
not be useless, but that's what you will have learned as you hold an
Amateur Radio license. 

The rest of the signal processing work will be completely new to what
most HAM license holders have learned to pass their license exams. In
fact, we don't work on alternating current any more, but on the time
discrete and amplitude discrete description of the alternating current.
In this sense we're just about to raise ourselves beyond the limitations
of alternating current and free ourselves from the laws of physics. 

Example: A resistor divider will apply a division raio to the voltage,
but the multiplication with 0.5 just does the same. A transistor
amplifier will increase a voltage by a certain ratio. In terms of
digital signal processing, it is equivalent to a multiplication with a
factor >  1. Using maths instead of hardware will allow a much higher
degree of flexibility and versatility, and it's just a matter of
software what you eventually want to do. 

It's a very recent revolution, and GNURadio together with the entire
range of recently available and in the meantime rather cheap devices
will allow us to participate. 

best 73

Am Freitag, den 25.12.2015, 15:18 +0100 schrieb Ralph A. Schmid, dk5ras:
> 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. 
> 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.
> Ralph, dk5ras. 
> > -----Original Message-----
> > From: address@hidden [mailto:discuss-
> > address@hidden On Behalf Of Daniel Pocock
> > Sent: Thursday, December 24, 2015 13:27
> > To: address@hidden
> > Subject: Re: [Discuss-gnuradio] ham/amateur getting started
> > 
> > 
> > 
> > On 24/12/15 08:31, Marcus Müller wrote:
> > > Forgot:
> > >
> > > [1] http://marcus.hostalia.de/sdra/pres.pdf
> > >
> > 
> > 
> > Thanks for the fast reply, I had a look and I notice you emphasize the USRP
> > products, you mention the B200 and B210 (the OZ9AEC link I found also
> > mentioned USRP but didn't specify model numbers)
> > 
> > I had a look at the FAQ[1] and spec sheet[2] to try and find comments about
> > amateur radio use cases, for example,
> > - how much TX output power?
> > - suggestions about use with an external TX power amplifier
> > - is RX or TX restricted on any frequencies by hardware?
> > - antenna impedance (50 Ohm?)
> > 
> > and I didn't find any comments on these things.
> > 
> > Looking at the accessory list I found that 782781-01 is a 50 Ohm cable so I 
> > guess
> > everything is 50 Ohm?
> > 
> > Even before getting into the software setup, is there any useful guide on
> > hardware considerations for SDR in an amateur station?  For example:
> > - power supply requirements
> > - risk of interference between difference devices in the shack, precautions
> > - use with other typical amateur equipment (antennas, RX pre-amplifiers, TX
> > power amplifiers)
> > - suitability for mobile use-cases, using DC/battery or vehicle power and 
> > with a
> > laptop or even a tablet as user interface
> > 
> > Any feedback or links would be really helpful, maybe they could go in the 
> > GNU
> > Radio wiki Ham page too.
> > 
> > 
> > 1. http://www.ettus.com/kb/detail/usrp-b200-and-b210-faq
> > 2. http://www.ettus.com/content/files/kb/b200-b210_spec_sheet.pdf
> > 
> > _______________________________________________
> > Discuss-gnuradio mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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