Software defined radios

I got kick started into Ham radio after building and playing with software defined radios.  2012 will be the year I got interested in radio, again.  I’ve been interested into radio since I was a kid growing up in rural plantation-era Big Island.  This interest waxed and waned in many forms over the year, but flared up recently after about software defined radios or SDRs from my friend Wayne KH6TZ.

SDRs are not the radios I grew up but  the concept is not new.  In the past decade, experimenters made the connection between the possibility of simple hardware and using their PC and the audio soundcard to create SDRs that anybody with a computer (lets say, a suitable computer) can build for way less than $100. In a way it’s a similar situation to the early days of computers when individual experimenters and hackers could create a new technology.  What’s happened is that this happened and the needed hacker level hardware and software is now available at low cost in the case of hardware, and for free, in the case of the requisite software.

The catch is that you have to build the radio hardware. Fortunately kits are available.  I started with the Softrocks.  Start somewhere.

Having a radio be dependent on the computer has disadvantages.  Computers are not ideal because they generally aren’t built with signal processing per se in mind.  Not every computer will work well as an SDR platform.  My five year old macbook doesn’t support any available SDR software that I know of for example.  My Dell 4700 XP box is noisy internally and goes only to 48 khz, compared to the laptop, not a good host for the SDR.  There are hurdles to work around, which makes this SDR project suitable only for techite experimenters.  One limiting factor with home computing hardware is the sound card.  The best sound cards in my household collection of computers and laptops provide about 96khz or almost  0.1 mhz of coverage at a time.   This is a useful amount of radio spectrum, but  in the overall scheme of things in the radio spectrum,  a very small slice.  This means that things get complicated when you want your SDR to cover, say 30 mhz of spectrum.  Whatever the limits, this is a great way to explore the world of radio.


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