Two transmitter pods on one tank??

[bmmills]

This might be a silly or naive question.

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?

Thanks all!

 

[steinbil]

If the transmitter fails it will be obvious, failure mode is disconnecting from the DC (as far as I know), so you just end the dive if it stops working. You should always know how much gas you have, and you should always have enough of a reserve to safely ascend sharing gas with a buddy, so making an ascent without being able to read gas should be a non-issue.

 

[Dapper Dan]

If the transmitter failed, I'd look at my SPG.
An AI transmitter is a convenience. I'm not throwing my SPG away because I have a AI computer. My buddy uses a Shearwater AI something-or-other, and he has a small SPG tucked away in his BC where he can use it if the AI Xmitter fails (and it has on several dives). "Lost connection" or "unable to connect" or something. He complains about it all the time.

There is no "level of safety" with only one device as unreliable as bluetooth IMHO.

 

[Dapper Dan]

Here's how I do it. One transmitter on the main tank, another on my pony bottle. Right wrist computer for main tank, left wrist for pony, and backup computer for my main tank in my BCD pocket.

So I've got 3 computers monitoring my Nitrogen exposure, with two independent transmitters. I also have a mini spg the size of a nickel on a thin miflex hose that runs next to my BCD inflator hose so it's like "a half a hose". That's more than enough redundancy.

I have never heard of anyone running 2 transmitters off a first stage and see no good reason to do so.

Sounds like a whole lot of confusion and hassle. Glad I don't have that kind of money. LOL

 

[Dapper Dan]

I clarified the post a bit as I saw you posted you were confused.

Hope that helps.

By the way I use an earlier generation Oceanic computer, I've got a whole bunch of them, as I watch for them to come up for sale, and I pay between $50-75 per unit. Sure the extra tank and regulator is a few bucks but I do a lot of solo diving and I'm often inside a wreck so I need it.

It wasn't the process that confused me, Brother. It was the idea of so much "redundant" gear.
When I was on the job I carried a backup 380 on my ankle.
I knew one deputy who carried one on the ankle and another in the crotch. One man - three guns. Always thought that was way overkill.

I've always felt that the concept of redundancy meant simple, convenient, effective, and fast. When you have too much "redundency" then it becomes inventory.

 

[dflaher]

But, does anyone dive with 2 transmitters on their own tank, to provide a level of safety if one of the transmitters die?

I think you'll find the best solution for this redundancy requirement is an SPG connected to your 2nd HP port. It's cheaper and more reliable. As long as your SPG and transmitter read roughly the same levels of gas, you can trust that your SPG is accurate if/when your transmitter fails...and safely continue your dive.

The issue with two transmitters is that if your computer fails, you're in a much bigger bind. Yes, it's another hose but it can be a short one clipped off to your left chest D-ring.

 

[scubadada]

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, one hardware failure and one over pressure valve failure. 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.

 

[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.