Mixed Radio-Acoustic Link for Control/Communications

[Slats]

-- Eventually the 74, 27, 40, and other kHz bands will be lost to us and we'll need a viable means of controlling our submarines.

David

I thought Mike said that he knew of some manufacturers staying in these bands?
Also - Engel in Germany have always sold Graupner and Robbe Futaba Radios to support their submarine line up, can I suggest that Mike contacts them for their take on the situation?

J

[He Who Shall Not Be Named]

It's not the manufacturers that are the issue. It's the FCC in America and the respective government agencies in other countries.

If not used or lobbied for, today's r/c frequencies will be re-assigned to other users.

Use it, or loose it. We don't have the clout of the AMA or other such National orginization; no one in Washington to insure that the bands we need remain for our exclusive use.

Now that the major users (aircraft principally) are onto the 2.5 gHz band, there is no one to lobby Congress to keep the lower bands restricted to r/c use. Any day now some big-time potential user of those bands is going to pay some Congressman off and we'll find ourselves outlawed from using our transmitters.

If the hammer does fall, all we'll have is the 27-band (the toy/Citizen's band).

David,

[Slats]

Gotcha - ****!!
J

[subchaser]

David:

The concept of a digital system as outlined is to digitize the control positions - eg of a sliding switch, off-on positions, etc with a basic 8 bit resolution (each value then represented between 0 and 255). So for example if the speed slider represented stop to full power, each bit would represent 1/255 or a resolution of about 0.4% of that speed/power range. This is usually more than adequate to control the speed or whatever.

My friend's thought model envisions 8 such channels (probably more than enough for most boats) each contributing a simultaneously sequentially sampled byte, followed by a CRC error check byte based on the previous 8 bytes, sampled at a little less than 50 hz. The bit pattern is then (in the simplest ASK modulation) imposed on the acoustic carrier (about 80 kHz say). A zero means zero amplitude and a 1 means the amplitude is full on. (Fancier multi-level/bit systems exist which reduce the transmission duration.) The band-width is about 4khz on a 80 khz wave.

I would envision a box with linear and rotating arms, on-off switches with led indicators, etc held by the operator with a wire leading to an acoustic transducer suspended from the surface near shore. On the sub there would be a minature (flat) receiver, buried say in the bottom of the boat, with the signal fed to the same kind of controller used with radio reception.

Some bells and whistles are needed. A problem occurs when there are multiple boats in the water where the commands can be confused. In that case it is useful/necessary to include an address byte so that a sub recognizes a message for it, and ignores others. Nevertheless with all transmitters going at 50 hz, ie every 20 ms, even if the message is only 9*8/80(000)=0.9 ms long, can lead to some confusion occasionally - but it will correct itself in a fraction of a second.

A much more versatile scheme is one where fewer but richer messages are communicated (Model C in my last posting.) This mimics the officer ordering the crew to perform individual operations. Conceptually it could be the 'captain' speaking into a head-mounted microphone, with the signal voice-recognized and converted by a minature computer into a command line which is sent modulated on the carrier from the nearby transducer. On reception the command line is converted to action by another minature on-board computer.

In other words one talks to one's sub.

The pond/lake etc could be filled with such boats but the chances of a command not getting through is very small, as the time between broadcasts is comparitively very long, and the transmiting duration is very short, and, if there is some confusion, each boat can demand a rebroadcast which quickly will arrive without interference.

Hope this helps. Your comments welcome.

[He Who Shall Not Be Named]

The Model C is a non-starter -- just too many commands leave the transmitter in any given unit of time (stick and switch strokes) while you drive the boat at speed, maintaining (trying to maintain) periscope depth. You just can't talk that fast!

On a real Submarine you have one guy on the fairwaters and rudder normally not taking direction -- other than depth and heading assignments occasionally barked out by the OOD or Diving Officer -- he's correcting changes in depth and yaw autonomously cause he's got a brain. The guy on the stern planes is also an automaton, only altering the boats angle when so commanded, otherwise, he's using his noggin too. Maneuvering maintains revolutions as per the last order from Control (the same idiot maintaining the boats bubble-angle twiddles the engine-order telegraph as commanded by the OOD). The Maneuvering guys yank the cubical sticks or fiddle with steam valves to maintain the ordered RPM's.

That's a lot of people involved in the maneuvering of one submarine.

On a model submarine only one bone-head is in charge of these four critical ship control operations (pitch, yaw, depth, and speed). We Driver's, with that transmitter in hand, can twiddle the sticks and mash the buttons just fast enough to get the sub where we want it to go.

My point is: You just can't talk fast enough, enunciate clear enough, and get the commands right the first time, to simultaneously effect those four critical ship control functions. Who would want to?! I need my voice to scream at kids throwing rocks, curse ducks, and shout out insults to other Drivers.

So, your C model is out.

Have you ever driven an r/c submarine?

As to Driver interface with the submarine using your acoustic method: Stick with the traditional transmitter. But, patch its encoder output to your transducer amplifier-interface, rather than the transmitters RF section.

David

[Subculture]

I'd say that for most model submarines 4 bit resolution (16 steps) would prove adequate, and probably wouldn't be noticed when compared with analogue resolution to the average skipper.

The funny thing with R/C today, is that despite all the bells and whistles tacked on, the vast majority of sets are still working with the 1960's PPM system. Things have moved on. Some manufacturers, like Futaba are supplying systems which bypass this system, but you're locked into buying their receivers, and the price makes my eyes water.