How software-defined radio could revolutionize wireless

[ChrisSmolinski]

In 1976, two shaggy-haired college dropouts founded a company called Apple to manufacture personal computers. The company's prospects looked so poor that the third co-founder relinquished his 10 percent stake in the company for $800 that same year. It simply wasn't clear why anyone would want the firm's Apple I computer. It was so under-powered that it couldn't perform many of the functions of mainframes and minicomputers that were already on the market. And most consumers had no interest in having a computer in their homes.

Today, of course, Apple is the world's largest company by market capitalization. What was important about the Apple I wasn't the meager capabilities of the original version, but the promise it held for rapid innovation in the coming decades.

Now, a company called Per Vices hopes to do for wireless communication what Apple did for computing. It is selling software-defined radio gear called the Phi that, like the Apple I, is likely to be of little interest to the average consumer (it was even briefly priced at the same point as the Apple I, $666.66, but has since been placed at $750). But the device, and others like it, has the potential to transform the wireless industry. This time, the revolution will depend on hackers enabled to manipulate radio signals in software...

Full article:

http://arstechnica.com/tech-policy/2012/07/how-software-defined-radio-could-revolutionize-wireless/

(I'm sure Fansome is incredibly excited by the continued advances of SDR technology)

[Lex]

Fansome, for one, welcomes our new SDR overlords.

I, on the other hand, am prepared with my dark glasses, bubble gum and shotgun.

[Fansome]

It's only fair to warn you Chris; I've tipped off the Amish about your new-fangled technology. They aren't pleased.

[Pigmeat]

You just cost the man his galena crystals,Al. Are you proud of yourself?

[cmradio]

Software defined control of a pentode RF/IF chain sounds good to me

Peace!

[ff]

Nice food for thought article Chris - thanks for sharing!  This might be a good area of experimentation for interested parties.  A low-power spread spectrum beacon shouldn't attract attention.  And if a few beacons were "around", the growing number of SDR owners could then experiment with decoding/demodulation.  Sounds like a really fascinating winter project to me, but I'll need to bone up on the theory a bit more.  It's been a long time since college...

[ChrisSmolinski]

Nice food for thought article Chris - thanks for sharing!  This might be a good area of experimentation for interested parties.  A low-power spread spectrum beacon shouldn't attract attention.  And if a few beacons were "around", the growing number of SDR owners could then experiment with decoding/demodulation.  Sounds like a really fascinating winter project to me, but I'll need to bone up on the theory a bit more.  It's been a long time since college...

A spread spectrum beacon sounds very interesting... I assume you could have a network of them, all on the same frequency. Might be neat for propagation monitoring. Since encoding is often easier than decoding, I wonder if there's a relatively low cost way to make the transmitters, so they could be located in remote locations, as is done now with the various CW beacons.

[ff]

A spread spectrum beacon sounds very interesting... I assume you could have a network of them, all on the same frequency. Might be neat for propagation monitoring. Since encoding is often easier than decoding, I wonder if there's a relatively low cost way to make the transmitters, so they could be located in remote locations, as is done now with the various CW beacons.

[/quote]

It's been a long time since I've dealt with any of this so I'm just floating trial baloons here, but I believe a DSSS transmitter could be done easily enough.  You would need to generate a pseudorandom code train and input it with the digitized audio signal into an XOR gate, then phase modulate a carrier with the resulting signal.    The receiver needs to sync to the same pseudorandom code train to retrieve the audio signal.  Several different transmitters can use the same chunk of frequency without interference if they all use different code trains.  An easy way to generate psuedorandom code is to use a linear feedback shift register - basically a shift register / XOR gate loop... two ICs...  At least that's how I see it.  Any input would be welcome...