Software Defined Radio

This page is all about my experiences with SDR, the future of radio, i think.....!

Recently i have been working on some of the microwave bands, 23cm and up and found that most stations are somewhere near the Frequency they are meant to be on but not exactly.... With only 2.7khz bandwidth normally it is easy to miss a station that is a few khz off my frequency. This problem started me off in looking at using the soundcard to 'see' a larger part of the spectrum where i was working.

Origionally i had used a IF downconverter from 455khz to 12khz for DRM on hf, but this worked quite well for my yeasu 736r as well but i could only see about 20khz of the spectrum..... now i wanted more!

Eventually i came across the softrock SDR receiver kit, it is a great kit for experimenting with SDR. It involved some Surface mount component soldering but not too big of a problem for most. It outputs the signal to the soundcard in I+Q format so that it is possible to see double the bandwidth that you would normally see with a standard soundcard.. ie. 48KHz.

I got version 6 which is designed for 80/40m bands selectable by jumper.

The kit looks like this when assembled.

More details to come soon but for now here is a screenshot of what you see on the software side of the receiver, it's centred around 3.750MHz.

Anyone know what the letter 'P' repeatedly in CW is about on 3.772?

Winrad with My Softrock V6 and my Soundblaster Live 5.1 card, (48khz)

Click photos for larger image.

The next image is with the new M-Audio Delta 66, 96KHz soundcard, it makes life a lot easier with it's breakout box on the desk rather than the ports on the back of the PC!

This Screenshot is of the 40m band on 25/5/06 at 9:30AM. Much less noise appears on the band with the new soundcard, which i narrowed down to a ground loop from the old soundcard to the psu on the softrock! Are the inputs to the Delta cards isolated from ground?

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Here is and audio sample recorded fromm the output of the Winrad software radio on 40m, 7.055MHz on 25th May 2006. at 23:33PM!

Now here's an nice screen grab.. See the CW contest on 40m....... WOW! Selectivity on cw in excellent even with these close signals!

SDR-IQ from RFspace

In december 2007 i finally managed to purchase one of these using from RFspace and am quite amazed at the possibilities that it has..

It covers from a few hunderd Hertz to 30MHz with a viewable span of 190KHz.

In the December EME contest i managed to use the SDR-IQ in conjunction with a 2m - 28MHz receive converter and my Yaesu 736R to look at the whole 23cm CW/JT65C portion to monitor activity.

Shortly i will add some of my recordings of the contest so you an heard what it is like to use a 2m dish on 23cm EME.