 My talk is on sound card based radio direction finding basically what what we're doing is locating transmitters and using simplified hardware that's cheap and so what's radio direction finding determining the direction that a transmitter is relative to a particular receiver if you have multiple stations you can do triangulation you can also do triangulation by making multiple observations this is like a single receiver so you're measuring the angle that the transmitter is relative to the receiver with one station or one observation you don't know exactly where they are but you know what direction if you have multiple observations or receivers you can do triangulation and get a pretty good idea of where that transmitter is there's a number of uses some of these are like emergency aid and rescue say someone's lost but they have some sort of radio you can probably help locate them locating jammers or interference of various sort there's people that do tracking for sport or tracking wildlife say endangered species that have been outfitted with transmitters finding interesting sources like police perhaps or military and tracking them basically this is your standard Doppler example as you move towards a source the radio waves compress and you get a higher frequency if you move away it's lower so kind of an example here normally the guy the girls on the left are twirling and as you're going towards and away from the horn you notice a change in the pitch and we're going to use this procedure to determine where they are but instead of you moving around you rotate your antenna and if you know where the antenna is and your received signal will have you'll you'll have two signals you have your antenna angle and then you have your received signal and you measure the phase angle and that will tell you the angle relative to the receiver that the transmitter is you do this a whole bunch and do and you average your measurements so you and do some filtering so basically you have your antenna rotation signal your Doppler shift you run that into your sound card measure the phase angle do some DSP GPS coordinates triangulation combined plot and coordinate with other stations or your own logs advantages low cost hardware you can do updates on the fly there's a lot of other things other advantages that that you can do by doing it this way there are some problems you do need a computer those are expensive you could also do it on a microcontroller with the standalone DSP and sound cards aren't the best analog to digital converters they do have some error and problems along with the the way that it works with the operating system this is black diagram of what I've been working on using a microprocessor and a cellular telephone antenna switcher they're pretty simple you only have two bits to control which antenna you're you're on and you switch between those quickly you get a pseudo antenna rotation target computer is about 300 bucks so we want this to be easily accessible you do need a radio however at this time this is kind of an example of what a single station that's driving around and making multiple observations might look like you can also do static stations there's a pretty good book about implementing practical DSP systems by Richard G. Lyons there's a good DSP intro course that's Creative Commons if you're interested contact me I can send it to you it was done last year at Tapper this is the antenna switcher that I'm currently using it's pretty small and very cheap it's under five dollars US for single quantities and I'm just using a spark fun breakout board to hook it up to the microprocessor and the antennas this is this is the antenna setup that I'm currently using it's pretty simple it's made out of tape measures and PVC pipe there's other variations that you could do like four cord wave whips there are some some problems if you were going after some something that was sensitive like police or something like that and you were coordinating over the internet and that you kind of expose your location in order to do the triangulation with other random people there there is a current working version that some Dutch guys built I'd like to make an open source hardware and software implementation some more information contact me via email thanks