Shearwater Transmitter Issues

[Capt Jim Wyatt]

I have two grey transmitters on my SM rig. When I got these transmitters a couple of years ago they were sold out of the yellow ones so I had to settle for two grey ones and was aware of the possible RF clashes with two like kind transmitters.
Yesterday the displays on the handset were intermittent for both transmitters. I removed both transmitter batteries and the voltage was measured at 3.0 volts and were replaced about 10 dives ago, or about 800 minutes of usage ago, or about 13 hours ago. New ones out of the pack measure at 3.2 volts. I think 3.0 volts should run these fine. ( I only use the CR2 Lithium batteries as prescribed in the user manual)

Battery warnings occur at 2.75 volts and I have seen no warnings. Battery life is predicted to be 300 hours according to the user manual.

So my thinking is that the batteries are OK. However is it possible / likely that I am getting that "Communication Collision" problem?

I turn on one tank and wait a few seconds before I turn on the other to help prevent the collision problem.

Any ideas?

 

[tursiops]

If "a few seconds" is close to five seconds, then collisions might be the issue.
Does each one seem to work OK on its own?

 

[passedoutwookie]

That sounds like the interference issue to me. I’ve experienced it before and lost all coms with both transmitters for 5-10 minutes. Then they would come back intermittently. This happened about 30 minutes into a dive. I only experienced this once in about 25 dives.

I added a swift transmitter and haven’t had the issue since.

 

[Capt Jim Wyatt]

Does each one seem to work OK on its own?

I did not check that -- but I will.

 

[Tracy]

How long did it last? I also run two of the older non swift transmitters. I have only ever had it happen once in the years of diving them but it cleared itself up and started working within 10 minutes or so.

 

[Capt Jim Wyatt]

It lasted on and off all of a 90 minute dive. 80+/-% of the time one or the other was not working.

About every 7-10 mins they would both display the pressure for 10-15 seconds and then drop off again.

 

[Cio]

Collision happens for 10 min and then clears. (In my experience)

 

[Capt Jim Wyatt]

Collision happens for 10 min and then clears

Then it does not happen again? Or what....?

 

[Cio]

Then it does not happen again? Or what....?

Then they just start working again without issue. Like off for 10 min then back on no sort of working period, just in and out.

Yours could be interference, maybe the timing on your units is very close? The clearing of the collision requires the timing fo the transmitters to be a tiny bit different so they drift out of time and no longer interfere. Technically the timing is the same but units are off by enough to allow many to use two gray ones, and I've read more than one person say it clears in 10 min. If it happens.

 

[Tracy]

Then it does not happen again? Or what....?

Not in the time frame of a dive.
If the two signals are broadcasting at the same interval plus or minus 20 milliseconds. eventually they will sync up and block each other out. They will also eventually work back apart and stop interfering. Think about a school bus with the two strobe lights on top in the fog. If you follow it long enough they will eventually be blinking in unison and then slowly come out of unison as the times aren't perfectly in sync. The transmitters work the same way.
You will most likely go years without them cross talking and if you see it on a dive, you most likely won't still be in the water when they overlap again.
If this was an ongoing issue for a few hours during a dive, there was something else happening.