Two transmitter pods on one tank??

[LI-er]

I have used my backup SPG 17 times.

Impressive that you remember exactly how many times you used your backup SPG.

I can't even remember a phone number when someone gives it to me.

 

[scubadada]

Impressive that you remember exactly how many times you used your backup SPG.

I can't even remember a phone number when someone gives it to me.

Spreadsheet

 

[tursiops]

Two transmitters on the same reg may mean -- depending on the brand/model of transmitter -- you get no useful data from either one because of the transmissions interfering with each other.

 

[Belzelbub]

I recently got my first dive computer with a remote AI tank transmitter pod. I love the functionality though as I’m aware that it makes me reliant on 2 batteries (in the watch and in the transmitter) I do run a backup computer that gives me air pressure via a HP hose.

I’ve read that most watch computers can sync to multiple pods. The use case most often marketed is to be able to see a dive buddy’s air status if they are close enough. But, does anyone dive with 2 transmitters on their own tank, to provide a level of safety if one of the transmitters die?

I don't know of anyone that does this. Depending on the specific transmitter, it may not even work. The reason I say that is because most transmitters turn on with tank pressure (or in some cases I've heard changes in tank pressure may wake them up). As they are both on the same 1st stage, and same tank, they will likely turn on at the same time.

This means the chances for signal collision are quite high. So two identical transmitters are likely going to step on each other's signal which likely means that the computer can't decode the signal.

There are a couple of ways I could see this working, but in most cases I don't think it will be successful, at least not with a single Dive Computer.

1. Using PPS transmitters (Oceanic, Shearwater, Aqualung, etc.) that are different colors (Gray, Green, Yellow). The different colors transmit at different intervals so if they do step on each other, they clear quickly.
2. Using a PPS transmitter and a Shearwater Swift (or just two Swifts). The Swift listens for a clear channel and only sends when it's clear.

 

[Divin'Papaw]

I agree with what a few have already said. If you want redundancy, run an SPG. Running two transmitters on the same reg may be problematic and may not provide the redundancy you are anticipating.

Whether to run a redundant SPG to your AI is another topic that has been hashed and rehashed on a number of other threads. Some run a redundant SPG, some don't. There is no right or wrong answer but rather it is a matter of personal preference.

 

[oya]

I use a single transmitter on my regs that are AI. No backup SPG.

I do suggest that people learn to calculate how much gas they use in a given time frame at given depths so that by the time you look at your pressure gauge you should simply be confirming information that you already know. That way, if a transmitter (or an SPG) fail, one should have some idea of how much gas remains in their tank to safely end the dive.

It's not essential at the recreational level... but it's easy to do and why not?

Modern transmitter failures are getting rarer and rarer as technology advances. To the point that I trust the transmitters as much as I'd trust any SPG. This from someone who talked smack about air integration for years and years.

Transmitter and SPG to me seems a bit "belt-and-suspenders."

Two transmitters is two belts.

 

[NauticalNick]

I use a single transmitter on my regs that are AI. No backup SPG.

I do suggest that people learn to calculate how much gas they use in a given time frame at given depths so that by the time you look at your pressure gauge you should simply be confirming information that you already know. That way, if a transmitter (or an SPG) fail, one should have some idea of how much gas remains in their tank to safely end the dive.

It's not essential at the recreational level... but it's easy to do and why not?

Modern transmitter failures are getting rarer and rarer as technology advances. To the point that I trust the transmitters as much as I'd trust any SPG. This from someone who talked smack about air integration for years and years.

Transmitter and SPG to me seems a bit "belt-and-suspenders."

Two transmitters is two belts.

I am the same way although obviously pretty novice. Transmitter being more accurate than a SPG too so I really don't see any value in lugging one around. You're not in deco, you know your gas and if things go haywire (as said, increasingly unlikely) you're ending the dive so I personally don't see any risk at all for recreational diving.

 

[bmmills]

Hi @bmmills

You already have a backup for your gas pressure, why would you consider a 2nd transmitter? In addition, the 2nd transmitter would eliminate the HP port you are currently using for your backup. You did not state whether your backup is a hosed AI computer or a SPG in a console with a computer.

I've been diving a computer for 22 years. My first computer was a hosed AI computer. From 2002-10 I dived that, most of the time with a backup non-AI wrist computer.

In 2010, I replaced the hosed AI computer with a wrist computer and transmitter. I continued to use a non-AI wrist computer backup and added a backup SPG.

In 2019, I acquired a 2nd AI wrist computer that runs off the same PPS MH8A transmitter as my other computer (yes, the computer from 2010 is still running perfectly, 1939 dives, 2035 hours)

Some consider my setup overly conservative. I have used my backup SPG 17 times. Most of these were my own fault, but I have also had 2 transmitter failures in 14 years. I have never lost a dive or interrupted a series of dives due to a computer or transmitter problem. I have not had the best of luck with my newest AI computer, it has been great that my old one has not had any problems.

The backup is a hosed AI computer

 

[Belzelbub]

The backup is a hosed AI computer

If that's the case, you are good to go. Probably don't have room for a 2nd transmitter anyway. It appears there may be a few 1st stages out there with 3 HP ports, but most are only going to have 1 or 2. You could add a splitter, but no point. You already have more redundancy than most.

 

[Whitrzac]

Can we beat this dead horse a little harder?


If you haven't looked at the spg in 100 dives, how do you know it works?