Tuesday, May 3, 2011

General Avionics Questions

Today the comment came up:

  Are there any pilots that, if you were designing and buying avionics for a Cozy panel from scratch..GPS/NAV/COM/GS/Intercom that would...price point for the GPS/NAV/COM/GS box could be in the $2-2.5k range

Well, I responded, and then I had some explaining to do. I went rambling on about Software Defined Radios (SDR), and I thought most people don't know what a software defined radio is. It is an amazing item, but so far they are kind of expensive (or not). The SDR is able to listen to multiple conversations at once. There are many ham radio operators that have SDRs on line. There is a WebSDR group, allowing multiple people to listen to radios all over the world. I said that right, one SDR can receive many conversations at once, allowing multiple people to listen to the same radio at the same time, on their own station! You can listen to frequency A I can listen to frequency B and someone else can listen to frequency C, each in their own mode (AM/FM/SSB etc). Also, with this software, you can "see" where the conversations are happening.

SDRs can transmit also. They are just as capable transmitters as receivers. They can operate in many modes, including TV (digital and analog). I think the first one was GnuRadio, and then TAPR got involved.  So far things are mostly aimed at ham radio operators, since like experimental airplane builders, they have more latitude within the rules.

Sounds complicated, right. Well, sometimes software is complicated, but people build fancy interfaces to make it simple. There will still end up being a lot of electronics in an SDR, but they are amazingly flexible. Depending on the design, some can do some amazing things.

Imagine flying along, and the GPS quits, (never happens right? check out http://raimprediction.net/applet.php, and look at the Grid Display Tool, click on the non-precision approach (NPA) button, all that red, hmm.. GPS isn't good enough to use for approaches), what do you do? Well, you have your SDR VOR receiver listen for a bunch of VORs, all at the same time. The receiver has a morse code decoder built in, and a database of VOR lat/lons. Just using triangulation, this sucker can determine where you are, with a reasonable degree of accuracy. Throw in some DME receiving, an ILS or two, and you should know where you are better than the GPS.

I envision some day, we will have devices we carry in our pockets that will be all SDR. So the smart phone that has become ubiquitous can do lots, but it has many radios, and they can be on a lot, burning batteries. How about the SDR having a smart mode, where the radio knows where you are, and uses the correct frequency in the one transceiver based on location.  Say you want to talk to someone across the room, why waste cell tower, use a different frequency, and talk directly to the person. Say you want to watch TV or listen to the baseball game on an AM radio, the SDR can do that. Need satellite radio, no problem.

As you can see, things are changing in the world of radio. No more random tuning and hoping, no more locking us in to old click click tuning, soon the radios will tune in to what we need.

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