Using PCM Radio For Data Transmission

[himszy]

Hi,

I'm designing the electronics for my automated underwater vehicle and am thinking about data transmission.....

The AUV will operate either under R/C control or fully automated transmitting data to the laptop in both modes over a distance of standard TX range. (It's being built purely as a 'can I do it' as opposed to something I'll actually use).

I was thinking since Wifi is out due to attenuation of using my existing PCM R/C TX but encoding data on each channel then hitting 'send', to be decoded on the other side...2 radio sets on two frequencies....

I was wondering if anyone had any better ideas? So far I've considered acoustic (extremely complex and low bandwidth) Wifi, as I said before the waves won't penetrate the surface, and this R/C solution.

It needs to be wireless and so that rules out a tether/umbilical....anything I've missed?

Spec:
Full-duplex system
Works underwater to a depth of circa 3m
Range circa 100m
Bandwidth 4 bytes/s

Michael

[AndyOne]

Try using 27Mhz, the RC sub boys seem to get their signals to penetrate to a certain depth. Failing this try a much lower radio frequency, the Navy use around 80kHz but this of course means you need an antenna about a mile long. Somewhere in between these would probably be OK for your application, the only problem will be getting a licence to operate.

Andy.

[vintage1]

Actually no one is going to notice a low power 80KHZ transmitter...and you can use a ferrite rod out of an old AM radio make a reasonable small antenna. Needless to say baudrate is execrably low tho. Probably use AM as FM is a bit f a pain at that sort of frequency..you'ld end up dividing down from an Xtal oscillator in the 1Mhz sort of region for FM..



ISTR that model subs work OK at 40 MHZ here..up to a range of a few tens of meters..and near the surface..at lest underwater you are reasonably free of interference..:D

[himszy]

Thanks Guys,

I've actually got an R/C sub myself so have some experience with them (40mhz), but just wanted to check that there wasn't a better way before I hacked up my radio :D

Michael

[vintage1]

If the pond is yours,,inductive loop wound round the bottom is good..Another option is ultrasonics.

[Nicetie]

Hi,

I'm designing the electronics for my automated underwater vehicle and am thinking about data transmission.....

The AUV will operate either under R/C control or fully automated transmitting data to the laptop in both modes over a distance of standard TX range. (It's being built purely as a 'can I do it' as opposed to something I'll actually use).

I was thinking since Wifi is out due to attenuation of using my existing PCM R/C TX but encoding data on each channel then hitting 'send', to be decoded on the other side...2 radio sets on two frequencies....

I was wondering if anyone had any better ideas? So far I've considered acoustic (extremely complex and low bandwidth) Wifi, as I said before the waves won't penetrate the surface, and this R/C solution.

It needs to be wireless and so that rules out a tether/umbilical....anything I've missed?

Spec:
Full-duplex system
Works underwater to a depth of circa 3m
Range circa 100m
Bandwidth 4 bytes/s

Michael

Think wireless dive computers. Check out how they send data from the
sensors to the wrist mounted display. (electromagnetic coupling)
Same with SCUBA voice transmission. Ultrasonic works too. You don't
really care much about data rate with a submarine.

Ken K5MBV