User manual Descent Mk2 pressure sensor

7000518 said:

Any idea why they chose sonographic transmission under water

Makes sense to me. The attenuation of sound waves is orders of magnitude smaller than at radio signals, hence it is limitting the problems of signal loss. And since you do not need to transfer any huge volumes of data, the sound wave is more than sufficient to send the pressure value to the watch every couple of seconds.

7000518 said:

i think that will complicate placement

Why exactly?

7000518 said:

Any idea transmitter frequencies for suunto, teric, ratio etc are under water?

Google tells for example 5.3 kHz at Suunto, 38kHz at Shearwater, and you'll certainly find the rest too, if you really want to know it. Typically, low frequencies will be used, because the higher the frequency, the worse the attenuation.

Ill take your word for it that sonic transmission is better than the khz frequencies of other transmitters,

regarding placement if your first stage has an spg its an extra hose, if not and you want rid of spg, its an extra hose, presumably unlike low kh frequencies it has to point at the watch, so you couldnt just leave a hose with transmitter dangling?

On a seperate note dont dolphins communicate with high frequency sonar, what about other marine life?

7000518 said:

regarding placement if your first stage has an spg its an extra hose

Well, I see no description of the system in the document you linked, just the sentence "Application Details Not Loaded Yet...Exhibits Not Loaded Yet...", so I do not know where the emitter will be. Do you have any background information, or why do you assume it will be in the SPG?

7000518 said:

presumably unlike low kh frequencies it has to point at the watch

Sorry, but I do not understand why it should point at the watch. Sound propagates in omnidirectional waves, just as radio waves do.

7000518 said:

On a seperate note dont dolphins communicate with high frequency sonar, what about other marine life?

Exactly, they do. And that's sonic communication, just like what you claim Garmin intends to use - you wrote "they chose sonographic transmission under water". Though, since the document is empty, I do not know whether it is true or not. The fact FCC is involved does neither deny nor confirm the claim.  Though personally I'd rather suspect radio transmission than sonic one, if FCC is involved.

Im not sure why the link isnt working, but in the manual on the link its says the device has to be 7cm away from diver and pointing away from the tank, so to me the best way to achieve that is on an spg type hose, below are links to screen shots of what it looks like and relevant manual detail, page 2 of 4 user manual qsm, can be accessed here

fcc.report/.../IPH-03550

The document is empty for me. Tried multiple browsers. Perhaps the content is blocked out of the USA

see above

Yes, this link works. Thanks, I'll look at it later. Time to sleep now

7000518 said:

but in the manual on the link its says the device has to be 7cm away from diver

Well, I really need to go to bed now, and have no time to read the full document, but it clearly tells:

Maybe you should sleep on it because youre responding to issues i havent raised, i never used the word maximally.

i prefer not to mount the transmitter directly onto 1st stage but use a short hose, personal preference, have to wait and see how this works in practice

Copied from the manual:

”On the surface, the sensor transmits using a 2.4 GHz radio signal. Underwater, the sensor transmits using a sonar signal.”

Sounds like an interesting solution. It also says you can pair your watch to multiple sensors, which would be cool if you have the same dive buddies.