Best signaling devices from the searcher’s point of view - update

[Dogbowl]

There is a positive correlation between PLB size, battery size, and transmission times.

I looked up the battery specifications for my ResQLink+:
- Battery, Operational Life Exceeds required 24 Hours @ -20°C
- Battery, Typical Performance 30 Hours @ -20°C

Quoting from http://www.mod.gov.cy/mod/cjrcc.nsf/All/3C7C04AC22F798D5C2257914002A9E24/$file/Information about PLBs.pdf
"According to the COSPAS-SARSAT regulations:
- A heavy duty battery class 1 must be able to transmit a signal for 24 hours at temperatures of -40°C.
- A class 2 battery must be able to transmit a signal for 24 hours at temperatures of -20°C.

Low temperatures shorten the life span of a battery so the above conditions represent the worst case scenarios. For example, at a temperature of 21°C the above batteries will function for about twice the time they would if they were at lower temperature conditions."

I may be able to get more than 60 Hours from my ResQLink+. Your PLB1 appearss to have a class 2 battery so you should be able to count on more than 48 Hours in warm water.

Looks like both the smallest PLBs on the market, and the ones I’ve been considering (i.e., PLB1 and ResQLink+) both have Class 2 batteries.

I wonder if there’s a PLB that has Class 1 batteries for longer battery time but yet still small enough to carry on a dive? Probably not...?

How about signal strength? Is that wattage?

 

[Dan]

Looks like both the smallest PLBs on the market, and the ones I’ve been considering (i.e., PLB1 and ResQLink+) both have Class 2 batteries.

I wonder if there’s a PLB that has Class 1 batteries for longer battery time but yet still small enough to carry on a dive? Probably not...?

How about signal strength? Is that wattage?

Both PLB1 & ResQLink+ send 5W of 406MHz signal. The McMurdo FastFind MaxG spec says >5W of 406MHz signal. I think you need at least 5W to send signal out to SAR satellites.

For surface-to-surface VHF signal MRG only sends out 1W of 161.975 & 162.052 MHz AIS and 156.525 MHz DSC signals. That’s why its battery life is last much longer than the PLB’s.

 

[Dan]

PLB needs such power to transmit signal to Low Earth Orbiting (LEO) satellites 515 miles (850 km) above Earth and to Geosynchronous Earth Orbiting (GEO) satellites 22,000 miles (36,000 km) above Earth.

http://www.sarsat.noaa.gov/UN_USA08/2009 USA Space Segment.pdf

This SAR service is free (paid by US tax payers, i.e., us, the Americans), so we might as well take advantage of it.

 

[tcpip95]

PLBs need that power to also transmit through thick tree canopies for land use as well. Also, weather conditions can also hamper the signal, and these are "must have" reliability situations.

 

[divinh]

For the dye marker, the first time I encountered it was about 15m underwater when I noticed that the water in front of me was turning glowing yellow/green. A diver in front was leaking the dye from his BC. I didn't know what it was initially and thought it might be some weird underwater coloration due to a thermocline.

For the Tektite, I have the marker light version, not the strobe version. Both look like they have two o-rings, but it seems like the second o-ring doesn't come into play until the light is turned on, which means most of the time, there's only one o-ring to protect from "bulb"/LED floods. Am I seeing this right?

 

[Dan]

For the dye marker, the first time I encountered it was about 15m underwater when I noticed that the water in front of me was turning glowing yellow/green. A diver in front was leaking the dye from his BC. I didn't know what it was initially and thought it might be some weird underwater coloration due to a thermocline.

For the Tektite, I have the marker light version, not the strobe version. Both look like they have two o-rings, but it seems like the second o-ring doesn't come into play until the light is turned on, which means most of the time, there's only one o-ring to protect from "bulb"/LED floods. Am I seeing this right?

For Dye Marker, I read that the Orion one (see picture, below) had some leaking problem at depth, as mentioned by @jsquaredFL on post #81, page 9 of this thread: Best signalling equipment from the searchers point of view That’s why I bought Divesoft Dye Marker, instead.

For the Tektite strobe, yes that’s the way it works. The double o-ring seal engage when you twist it ON. That’s why I don’t take it diving as is. I put it in a 100’ (30m) waterproof rate pouch. Another reason I put it in the pouch is that I don’t want to accidentally turn it on in my BCD pocket or flood it by accidentally twisting it while sticking my hand and pulling something out of the cramped-up pocket.

The same design is used in my night dive marker. That’s why I only put the night dive marker & turn it ON before jumping into the night dives. I’ll remove it off my regulator, dry it & store it after the night dive is finished.

 

[CWK]

I've been reading up on PLBs and have found some points of interest:

1. From: http://sdcap.us/wp-content/uploads/2016/10/ResQLink-Manual.pdf
The same GPS data will be sent with each 406 MHz signal for the next 30 minutes. At that time the internal GPS will start up again, search to find your LAT/LON and incorporate it into your next 406 MHz signal. [Note: GPS position is only refreshed every 30 minutes on the ResQLink because it is battery intensive. Other PLBs shoul have similar considerations.]

2. From: Small and Light Personal Location Beacon (PLB) | FastFind 220
A PLB uses an internal GPS receiver to pinpoint your location to within 62m. Once in the area, rescue services are then able to pinpoint your precise location using the inbuilt 121.5Mhz homing transmitter. [Note: 121.5Mhz is the aircraft emergency frequency.]

3. From: http://oceansignal.com/wordpress/wp-content/uploads/1364301061_PLB1_User_Manual.pdf
Because the test transmits a short burst on the aircraft distress frequency of 121.5MHz, please
only carry out this test in the first five minutes of each hour.
It is recommended that you test your PLB once a month. [Note: Monthly testing is only for the basic test, not the GPS test.]

4. From: http://oceansignal.com/wordpress/wp-content/uploads/1364301061_PLB1_User_Manual.pdf
Warning : As testing the gps receiver expends significant amounts of battery energy do not test the gps operation more than once a year.

 

[CWK]

I have been trying to find out how often the MRG acquires a new GPS position. I imagine that it may be similar to PLBs and only acquire a new GPS position every 30 mins. However, the user manual is silent on this point. The manual, however, does say, "Performing a test will reduce the battery life. Only perform a test once before each dive trip."

 

[Dan]

I have been trying to find out how often the MRG acquires a new GPS position. I imagine that it may be similar to PLBs and only acquire a new GPS position every 30 mins. However, the user manual is silent on this point. The manual, however, does say, "Performing a test will reduce the battery life. Only perform a test once before each dive trip."

According to Ryan of Nautilus Lifeline:
“The frequency with which the signal is transmitted is based upon the ITU and FCC standards”

 

[CWK]

Both PLB1 & ResQLink+ send 5W of 406MHz signal. The McMurdo FastFind MaxG spec says >5W of 406MHz signal. I think you need at least 5W to send signal out to SAR satellites.

For surface-to-surface VHF signal MRG only sends out 1W of 161.975 & 162.052 MHz AIS and 156.525 MHz DSC signals. That’s why its battery life is last much longer than the PLB’s.

Perhaps it is not just the transmission power (5w vs. 1W) but also the ability of the satellites to detect signals that should be considered.

From: Satellite AIS
"Both Class A and Class B AIS transponders are detectable by S-AIS, however Class A transmissions are more likely to be detected for the following reasons, among others:

• A Class A transponder has a higher transmit power of 12.5 watt, compared to a Class B at 1-3 watt on average"

From: http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1543&context=lawpapers
LEO satellites used for Satellite AIS typically have anorbital period of approximately 90 minutes.

The MRGs 1 W transmission may (or may not) reach LEO satellites used for S-AIS. Although AIS was initially envisioned for terrestrial use, S-AIS has evolved and more applications (SAR?) may develop.