Scuba diver's Personal Locator Beacon - how never to be lost at sea

[DandyDon]

DD, there is little need for the PLB at most sites. Where needed, my dive op has Nautilus Lifeline units.

Finally, the rest of that story - ok.

Want to sell the canister? Well, I guess it's a larger model...?

Nah, it's not too big. I wouldn't replace it either if I got free batteries. We who have to pay for batteries have a different view, but still - $50/year to have one is a good idea, as it was when you got yours.

 

[Mike]

So...the 12 mile range they claim for the VHF is incorrect?

**edit.. actually they say the DSC Range is 8 miles and voice communications is 4-5 miles

The range for VHF transmission is typically the square root of (the antenna height times 1.5) It's also a function of the transmission power and weather conditions.

Nautically speaking small boat to small boat VHF range is usually considered about 5 miles, that's with a small boat which means the antennas are likely somewhere around 8-15 feet off the water.

square root of 12x1.5 = about 4.5 miles

A diver bobbing in the water has what, about a 2 foot high antenna with a nautilus while speaking into it? Let say 3 feet for giggles...

Square root of 1.5x3 = just a shade over 2 miles.

Throw in bad weather with large waves blocking the signal anytime you're in the wave trough, throw in rain... you're range goes down even further...

 

[DandyDon]

You see a lot of claims about the radio range on various sales sites, but none on the Nautilus site. The claims on the GPS distress signal are greater, but I'm sure it all varies as much as my car radio's reception - how far from the transmitter I am, how strong, interference, etc.

 

[cvchief]

The range for VHF transmission is typically the square root of (the antenna height times 1.5) It's also a function of the transmission power and weather conditions.

Nautically speaking small boat to small boat VHF range is usually considered about 5 miles, that's with a small boat which means the antennas are likely somewhere around 8-15 feet off the water.

square root of 12x1.5 = about 4.5 miles

A diver bobbing in the water has what, about a 2 foot high antenna with a nautilus while speaking into it? Let say 3 feet for giggles...

Square root of 1.5x3 = just a shade over 2 miles.

Throw in bad weather with large waves blocking the signal anytime you're in the wave trough, throw in rain... you're range goes down even further...

I believe you might be correct, IF it was one lifeline talking to another lifeline at the same height. You are failing, I believe, to consider the height of the receiving antenna. A taller antenna can 'see' farther before the curvature of the earth gets in the way and can receive signals from farther away.

One of the lifeline success stories was about someone trying to hail their boat, but instead got the Coast Guard who could hear them (big antennas) and relaying the info to the dive boat.

On the other hand, my Lifeline that I sent in for service was inside a building laying on a work bench somewhere around Vancouver. Say what three feet high and probably at least 8 DB loss from the building. It apparently went off on the bench. I got the call on my cell from US Coast Guard in Puget Sound. Once I explained the situation they asked if there was any way I could help them contact the company because the Lifeline emergency alert function was tripping the Coast Guard emergency function on their VHF system all around the area. They told me the Canadians were having the same problem. I was able to find an emergency number for the company and contact them. Apparently it worked REALLY well.


I mean I get it that you don't like the VHF radio idea, but it has it uses. The sat is more like a nuke.

 

[Ron Lee]

Apparently it worked REALLY well.


I mean I get it that you don't like the VHF radio idea, but it has it uses. The sat is more like a nuke.

It worked really well on the surface of land...when it was not needed and could cause the most OOPS.

Use what works for your perceived need. Yes a PLB (or EPIRB/ELT) is calling in the big guns but in a serious situation, I would not hesitate to use mine. That is after all other options are exhausted.

You do not use it to complain about the lack of McDonald's nuggets on a hike in the forest.

 

[Sideways]

You see a lot of claims about the radio range on various sales sites, but none on the Nautilus site. The claims on the GPS distress signal are greater, but I'm sure it all varies as much as my car radio's reception - how far from the transmitter I am, how strong, interference, etc.

I noticed the claims from different vendors also Don. The numbers I posted in my edit are straight from the owners manual. (pg. 13)

http://www.nautiluslifeline.com/pdf/NLL_OperationsManual.pdf

 

[Mike]

Cvchief - I don't dislike the VHF radio at all. Don't confuse dislike with just having a working knowledge of VHF. I know VHF, I've owned a boat and used it, VHF has it's use, but there is a reason people have SAT phones and EBIRBS on board boats also.

 

[Sideways]

I'm actually starting to entertain a similiar Idea Mike. Maybe get one of each. Give my wife (dive buddy) the nuke, and I'll have the lifeline. In a perfect world I guess we'd have both rolled into one, like you mention. That way we had both a "light" and "dramatic" option all in one.

 

[Mike]

Yep, when Nautilus comes out with a PLB built into their Life Line, they will have the ultimate product and I'll be the first in line to buy one.

 

[cvchief]

Cvchief - I don't dislike the VHF radio at all. Don't confuse dislike with just having a working knowledge of VHF. I know VHF, I've owned a boat and used it, VHF has it's use, but there is a reason people have SAT phones and EBIRBS on board boats also.

If you have experience, you should give credit to the actual capability of the VHF. My experience is limited mostly to only UHF, VHF, 800 P25. Most of the VHF on the low side though, not so much in the 150s, but a little.

For instance, we use some UHF handhelds that won't reach far at all between each other, especially with UHF being more line of sight than the VHF. However, it has a very nice range when reaching out to a tower, making great for a duplex talk around. That is because of the height of the receiving antenna.

Maybe Dave will pop in and give us some idea of range on the lifeline to a tower, but it is much more than your estimate.

I would like to add a PLB to my gear repertoire. I just picked the something with the capability of being useful more often first.