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Sunday, 17 July 2016

SDR with the Red Pitaya

Well,

I came accross this board on the RS Components website, it's called a Red Pitaya:


Now this board is very much designed with RF and SDR (Software Defined Radio) in mind, it's got some very high speed ADCs (Analogue to Digital Converters) and DACs (Digital to Analogue Converters) on board - it also has a SoC (System On a Chip) with an ARM processor and a FPGA (field programmable gate array) pluis a whole other bunch of useful stuff also on-board.

Now, there's a very clever chap Pavel Demin who has written some fab and groovey software for the board to try a whole bunch of stuff from a simple SDR receiver all the way to a VNA (Vector Network Analyser). There has also been some interesting introductory articles to the board published in the Data Modes column in Practical Wireless.

I've been playing with the WSPR decoding software as a starter-for-10.

You have to go and get the software from the website here. You can download an image of the Red Pitaya boot device (memory card) and create the memory card for the device to boot from - I used Win32DiskImager for Windows - you could also use DD for Linux.

Once you have that device created you can boot the board from the card, then you need to access the board from your network - I used Advanced IP Scanner to find the board and then used Putty to create a SSH connection. From there it was a simple task of editiing the decode-wspr.sh file, adding my callsign and grid square and then rebooting.

I have the board configured (by editing the write-c2-files.cfg file) to decode 8 bands similtaneously (yes that's correct).

Here's a map of my decodes with the Windom connected to the input connector of the Red Pitaya (via a small attenuator pad for impedence matching).


I've also tried the SDR Receiver software with HDSDR configured to conenct to the RedPitaya SDR accross the network - it worked superbly.

I now intend to try to get the TX side of the SDR functioning - using WSPR first. To facilitate this we will need a bit more hardware. I found a great buffer amplifier design by SV1AFN here. I ordered the PCB only from him and here's the finished article (I am one SMA connector short of a party):


I'll also need a TX RX switch which I will create using a latching SMA relay I have here and a kit from W6PQL.


To move on to the VNA experiments I will need some other bits and bobs including this:


So, much more to follow!

Here' our Choppsy cat (AKA Git Basterd Cat from Hell):


Good, egh? Local conditions.

2 comments:

  1. Hi... between your experiences and those of Mike G4WNC in Practical Wireless, I splashed out and got rn RP myself. Having a lot of fun with it. I was wondering could you clarify this extract from the blog post: "a small attenuator pad for impedence matching"

    Best regards
    Gerry / EI8DRB

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    Replies
    1. Hi Gerry - I just used a 3dB pad between my Windom and the RP. https://www.pasternack.com/t-calculator-pi-attn.aspx?gclid=CjwKEAjwz4u9BRCbioK3stnBznESJADA75xb5jQxQej02mKUHm32vB0vx89Kll8QwZlowXMXjvv36BoCFVLw_wcB

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