SDR (Software Defined Radio) Transceiver

[pavel]

1) Your software is an SD Card image - I have a spare MicroSD card, is it as simple as using the card with your image when I want to use the SDR, then switching back to my other card when I want to run the other apps and stuff I've already put on it?

Yes, you can switch between two SD cards.

2) Do you have any suggestions for antenna's - there is too much information out there, we are currently looking at building either a long wire or di-pole type antenna - probably hang something between tree's in our back yard.

I'm afraid that I can't help you much with the antennas. However, I've found a very interesting article about the amateur satellites (antennas are discussed on page 14):
http://www.amsat.org/amsat/ftp/articles ... asysat.pdf

According to this article, a dipole should be OK.

[makerkatie]

Pavel - Thanks again for your help. Have found plans for a simple dipole, and ordered parts from Amazon. Will post in a few days time once we've had chance to put everything together and tried it out.

[turboturbine]

Question, does the RP also work as a transceiver with HPSDR? I found a readme file dspserver from pavel where HPSDR is mentioned.
HPSDR has deversity noice cancelling, I do not know if gnuradio supports that. It would be really nice.

[pavel]

Question, does the RP also work as a transceiver with HPSDR?

What do you mean by HPSDR?

[pavel]

OK. I've found some information about diversity on the openHPSDR wiki:
http://openhpsdr.org/wiki/index.php?tit ... i-Receiver

Dual Mercury board setups (Windows): Diversity operation using two Mercury receiver boards is implemented in Open HPSDR PowerSDR. Polarization diversity or spatial diversity are possible, depending upon what inputs are provided to the two Mercury boards.

It's not impossible to interface the Red Pitaya SDR transceiver with PowerSDR. I even downloaded the latest version of the Open HPSDR PowerSDR source code and installed MS Visual Studio 2013 a couple of weeks ago. However, I don't see from where to start. All good ideas are welcome.

I'm looking at the code from the following subversion repository:
http://svn.tapr.org/repos_sdr_hpsdr/tru ... DR_mRX_PS/

[Nils Roos]

I'd say you want the Red Pitaya to pose as dual Mercury boards connected to a Metis adapter. There's a description of the communication protocol (pdf) that is in agreement in with code from your target repo.

It works as follows:
PowerSDR: broadcast discovery message
Metis(RP): wait for broadcast and send reply
PowerSDR: register discovered boards, send start command
Metis(RP): stream sample data or I/Q

[pavel]

I'd say you want the Red Pitaya to pose as dual Mercury boards connected to a Metis adapter.

Thanks for the great idea, Nils!

It reminded me about the RTL to HPSDR software translation server.

With the Red Pitaya to HPSDR software translation server, it would be possible to use Red Pitaya with all the OpenHPSDR programs: PowerSDR, cuSDR, openHPSDRJ, ghpsdr, ghpsdr3, ghpsdr3-alex.

[turboturbine]

That would be great, the only thing I can find that comes the nearest to open HPSDR's diversity phase filtering in GNU radio can be find when searched under MIMO but in my short search I can only find details about synchronized transmitters and combining there ouput power, thats not what I want. I do not know whats easier to archive, getting the RP to work with open HPSDR or adding such diversity capability to GNU radio, open HPSDR looks like a very nice piece of software to me! I think other radio enthusiasts will agree, GNU radio is more some kind of development envoirement not really targeted to radio hobbyists who will still like the measuring applications which are available for the RP!
I have also seen a video from someone connecting two RTL dongles to open hpsdr, do you think it is difficult to let the RP work with the open HPSDR software? I mean the software translation server, lots of programming or only configuring? And also can the RP be used as a TRX or only RX in this manner? And another advantage would be that you can probably use sstv!

[pavel]

I have also seen a video from someone connecting two RTL dongles to open hpsdr, do you think it is difficult to let the RP work with the open HPSDR software? I mean the software translation server, lots of programming or only configuring?

For me, the main difficulty is that the Red Pitaya ADC sample rate is 125 MSPS. It would be much easier if the Red Pitaya ADC sample rate would be 122.88 MSPS as it's the case for all the openHPSDR hardware.

It's of course possible to use the sample rate conversion libraries such as libsamplerate or libsoxr but Red Pitaya CPU is not powerful enough to run these libraries at 500 kSPS.

I've just checked that with the fastest settings (SRC_SINC_FASTEST) libsamplerate can process two RX channels with samples rates not greater than 250 kSPS when running on Red Pitaya.

So, to support all the openHPSDR sample rates (48 - 392 kSPS), the translation server should run on a PC communicating with both Red Pitaya and openHPSDR software via the network.

[Nils Roos]

Sample rate conversion seems to be the kind of repetitive DSP task that FPGAs are good at. Maybe a solution in logic is feasible ?
I think the usual way to achieve this is to use oversampling followed by a filter that generates output at the target rate. If we target 392kSPS as the highest rate, the input signal can be effectively considered oversampled already, so it boils down to a suitably clocked filter. (please view this as a back-of-the-envelope concept, I freely admit to having only a laymans knowledge of signal processing)