Guys,

Sorry about the confusion. I'll try to be a little more descriptive of what this is about.

Irving - only requires the internet to download whatever software package and add-ons are needed. Operating doesn't use the internet at all - you just need to be able to power whatever computer is running this.


OK, now I'll try to discuss the big picture and what this is good for. I apologize for being so long-winded!

Radio Frequencies include tons of communication stuff. Some are ham radio bands, some are emergency services bands (police, fire, ambulance, ems,...), some are public service frequencies (XCEL energy and Kelly's crane operator, for example), some are aircraft, some are marine, some are local communications like CB, FRS/GMRS, MURS, etc. Some are analog, some are unencoded digital, some are encoded digital, some are broadcast radio stations (both AM and FM), some are voice, some are CW (morse code), some are digital (like packet, D-Star, MOTOTRBO, and P-25).

Covering everything used to take several pieces of gear, including ham radios, wideband communication receivers, and shortwave receivers - and knowledge of how to operate all of them. A BIG investment of $$ and time. Several years ago, radios and receivers started to include full-blown computers as their core, instead of RF discriminators, analog filters, analog tuners, and all of the other hardware needed to make a complete radio/receiver. That old hardware tended to be very expensive, and often require precision components. As you know, computers have gotten more and more powerful over the past 34 years since the IBM PC. Prices have come down and you get more and more technology for less and less money. I used to design PCs back in the 386/486 era, and all smartphones today are much more powerful computers than the most powerful 486 computer in 1986-87.

What companies discovered over time is that the complex RF (radio frequency) functions performed by an old-school radio or receiver can also be performed by a computer. You must first convert RF signals from an antenna to baseband analog, then from baseband analog to digital (That's what happens in the USB dongle I mentioned in the OP). Once in digital, software that runs on the computer can do very complex things on the digital data stream like discriminating, filtering, and so on. The software contains very complex algorithms that perform digital signal processing and other functions, while running a graphical user interface that allows a user to understand what the antenna is receiving.

The ham radio world is full of hobbyists that love to experiment and try new things - many are not in it to make $$ and this is what they do for fun. That is the genesis of software-defined radio (SDR). Now, there are many full-fledged companies that sell very feature-rich SDRs - usually at a discount to what a conventional radio with similar capabilities would cost. (Note: "conventional" radios these days contain most of the computer hardware within, which is not exactly what is in a PC, but similar). SDRs use off-the shelf computers like desktop computers, notebook computers, tablets, and in some cases smartphones - for the computer functions. The computers run todays PC Operating systems - XP, Windows 7/8, Apple, Linux, or even Android.

The term "SDR" these days usually means a ham radio implemented as a conventional antenna (for whatever bands you want to use), an RF converter box (like the USB dongle, but more capable), and software applications you buy from the SDR manufacturer. The term "SDR" also seems to be used for the USB scanner dongles and associated software. BTW, the USB scanner is really nothing more than a TV tuner! The idea is you could watch broadcast TV on a computer somewhere, even without an internet connection. Several years ago, TV signals in the US were broadcast over the RF frequencies - but then the FCC eliminated broadcast TV. Now it requires a cable or a satellite feed in the US. However, broadcast TV is still happening in much of Europe, so these TV tuner dongles sell like hotcakes over there.

One very cool part of SDR (the scanner paradigm) is the software is free and it gets better and more feature-rich all the time (and you don't pay for the upgrades either)! Everyone owns a computer, so the most expensive hardware is usually already paid for. All that is needed is a way to get the signals (antenna and dongle) into the computer. Yes, you can go and buy a high end Uniden digital trunking scanner for $600 - but even that doesn't do everything a scanner SDR does. The biggest thing the scanner SDR does NOT do is decode encoded transmissions, but no gear available to the general public does that anyway.

I wouldn't call my setup "portable" or even "mobile" - although with a different antenna it could be. I plan to use it for (mostly) local situational awareness at my house in the event of a natural disaster or a grid down/social unrest situation.

BTW, a book a recommend very much is "Grid down communications" Volume 1 by Sparks: http://www.lulu.com/us/en/shop/spark...-21547051.html
For $11 includes lots of useful info on lots of comm options. It came out on March 24th of this year, so it is very current.

I hope this helps, guys. Although SDR is getting more and more popular, there are still many who have never heard of it. There are lots of Youtube videos and internet sites that talk a lot about SDR and show it in use. My take is that for $75 this is a no-brainer that with some practice can provide a huge upgrade in awareness. It by no means replaces ham radio and I think ham radio gear is very complementary to the scanner SDR capabilities.