Originally Posted by AdamY
I dont get why we cant make one of these. If you could take a VHF
, tune it to the frequency and then feed that undisciminated signal into a laptop
using a standard stereo mini cable you would be in business, this should be doable for much less than the prices these AIS
systems are charging
It could be done if somebody felt like putting the effort in to it. There are two frequencies to monitor
; it is unclear to me whether you can get by monitoring only one. The data rate is too high (9600 bps) to use the speaker output from the radio
, so you need to get the FM discriminator output directly. The sound card input should have a high enough sampling rate to distinguish the bits.
After that, it's "only" a matter of writing a program to extract the HDLC frame from the audio input, extracting the data from the transmitted packet, and finding a way to do something useful with the data. Probably you would end up writing a Windows device driver that looks like a serial
port sending NMEA
data, so it would work with existing applications.
The hard part of all this is the detail of design and programming. If you did this as a commercial
endeavor, you would have expensive software
instead of expensive hardware
. (ok, you still need the radio
...) If you do it as a hobby, your time is free.