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#254551 - 12/11/12 07:33 PM Re: Let's Talk PLBs...... [Re: JohnN]
Doug_Ritter Offline

Pooh-Bah

Registered: 01/28/01
Posts: 1930
Originally Posted By: JohnN
It would be interesting to know if the manufacturers even plan to do the battery replacement of your 6-10 year old unit. That would require them to keep spares (that have a shelf life), and the labor to open, replace, reseal the units. You could imagine it might make sense for them to simply send you a lower end current unit.

-john


WRT replacement batteries, due to expiration dates, nobody really "stocks" these for any distress beacons. They generally build to order or once they have a period of consistent sales history, will build to anticipated sales based on that. It is a PITA for the manufacturers and PLBs are headed to becoming throw-away items (but, please don't actually throw them away in the trash without disconnecting battery). EPIRBs and ELTs are a different matter being used in mandated carriage and these they can plan on replacement with required inspections that ensure sales of replacement batteries for a period of time. In any case, no way this will ever be cheap done correctly and considering market size, etc.
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#254572 - 12/12/12 08:07 AM Re: Let's Talk PLBs...... [Re: Doug_Ritter]
ChicagoCraig Offline
Member

Registered: 11/30/09
Posts: 113
Originally Posted By: "Doug_Ritter"
Penny wise, Pound STUPID!


Yup. Agree. Battery replacement service is more than just replacing the battery.

http://www.acrartex.com/support/faqs/personal-locator-beacon-faqs/#q-4722

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#254796 - 12/20/12 10:06 PM Re: Let's Talk PLBs...... [Re: hikermor]
spuds Offline
Old Hand

Registered: 06/24/12
Posts: 822
Loc: SoCal Mtns
So for a schmuck who knows nothing,is the ResQlink the one to have?

What other models?

Best price per ability on units?

I want it for if truck goes over the hill or stuck in snow storm.

Is snow an issue for these things to work,have to wait for clear weather?

Would this work in a collapsed building or line of sight to sat essential?

Experts,need your advice!

Edit-looks like resqlink is the ideal?


Edited by spuds (12/20/12 10:44 PM)

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#254808 - 12/21/12 02:28 AM Re: Let's Talk PLBs...... [Re: spuds]
hikermor Offline
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 5797
Loc: southern Cal
You will find DR's analysis of the available units most informative. Check the main portion of ETS.

I am probably going to get the ResQLink, primarily because of the compact size and low weight. If you are going to use your PLB in conjunction with a vehicle, that probably need not be an important consideration.
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#254816 - 12/21/12 03:52 PM Re: Let's Talk PLBs...... [Re: hikermor]
Montanero Offline
Old Hand

Registered: 10/14/08
Posts: 1051
Loc: North Carolina
The Res-Q-Link does not float, so get the pouch that they sell that will make it float in case you are going to be around water. It also is a convenient belt pouch for it. It is small enough that it is easily carried in a pocket though.

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#254818 - 12/21/12 04:03 PM Re: Let's Talk PLBs...... [Re: Montanero]
Russ Offline
Carpal Tunnel

Registered: 06/02/06
Posts: 4461
Loc: SOCAL
My ResQLink is carried in a pouch on my aviation survival/flotation vest. Besides the pouch, it is also tied in with a paracord lanyard. It doesn't float and in the environment I could use it, the water is very deep, so I keep it firmly attached to something that will float -- me.

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#254820 - 12/21/12 05:11 PM Re: Let's Talk PLBs...... [Re: spuds]
JohnN Offline
Old Hand

Registered: 10/10/01
Posts: 966
Loc: Seattle, WA
Originally Posted By: spuds
So for a schmuck who knows nothing,is the ResQlink the one to have?

What other models?

Best price per ability on units?

I want it for if truck goes over the hill or stuck in snow storm.

Is snow an issue for these things to work,have to wait for clear weather?

Would this work in a collapsed building or line of sight to sat essential?

Experts,need your advice!

Edit-looks like resqlink is the ideal?


You should be able to buy a compact GPS enabled PLB for around $250 these days if you look around.

Examples:

http://www.landfallnavigation.com/fastfind220.html
http://www.landfallnavigation.com/acr375plb.html

-john

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#254828 - 12/21/12 11:33 PM Re: Let's Talk PLBs...... [Re: spuds]
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 1960
Loc: NE Illinois
Originally Posted By: spuds
I want it for if truck goes over the hill or stuck in snow storm.

Is snow an issue for these things to work,have to wait for clear weather?

Would this work in a collapsed building or line of sight to sat essential?


I'll make an attempt to answer your questions about how the PLB will operate in poor weather and/or poor light-of-sight conditions.

When a 406 MHz PLB is activated it transmits a signal that identifies the PLB (I assume there is a unique ID code).

If you are in a latitude between 70 degrees north & 70 degrees south that signal will be picked up almost immediately by geostationary (GEO) satellites that are positioned at the equator.

If you are not within that 70 degree latitude area - or marginal - that signal can still be picked up by low-Earth orbiting (LEO) satellites. Because LEO satellites have a more narrow view of the Earth it may take some time for one of them to come into "view" of your PLB signal. This potential time delay is longer at the equator and shorter at the poles - up to 1.5 hours. The maximum delay in the United States is about 1 hour.

It is my understanding that transmission of the PLB signal to the GEO and LEO satellites does not require direct line-of-sight, and will do well even in poor weather. The effect of mountains and buildings in blocking the signal will depend on the type and location of the receiving satellite - your mileage may vary there.

Receiving the PLB signal alone is of limited benefit if the system does not know your location.

There are two methods of identifying the location of the PLB signal: GPS and Doppler. The GPS method requires a clear view of the sky, but the Doppler method is more robust and shouldn't be impacted by weather.

GPS:
If your PLB is equipped with a built-in GPS capability, AND you have a reasonably clear view of the sky, AND the GPS has succeeded in locking in on enough GPS satellites to provide position coordinates, then the PLB transmission will include those position coordinates to both the GEO satellites (potentially instantaneous) and the LEO satellites (may be delayed up to 1.5 hours). The accuracy of the GPS position is within about 400 feet.

Historically GPS has required a fairly clear view of the sky, but in the last few years more advanced GPS chipsets can lock onto GPS satellites even without a direct view of the sky (under vegetation, inside buildings, ...). I'm pretty sure all modern PLBs have those more advanced GPS chipsets.

Doppler:
If your PLB is not equipped with a built-in GPS capability, or you do not have a clear view of the sky, your position can still be determined by the LEO satellites using a Doppler effect - though there can be that delay associated with the LEO satellites. The accuracy of the Doppler position is within 1.2 to 3 miles, but averaging about 1.5 miles.

Note that because the GEO satellites are geostationary there is no Doppler effect - they aren't moving relative to your location, so they cannot find your location using this method.

It seems to me that the +/-1.5 miles area is pretty big, but its far far better than no location information at all. At least they will be looking for you nearby.

DO get a PLB that has an onboard GPS capability.

If you activate the PLB, then you'll want to give it as good a view of the sky as you can. If you're in your vehicle, put it outside. If you're in a collapsed building, put it near a window - or an opening if possible. Getting that GPS position means they'll essentially come right to you. Without that GPS position they'll need to search for you which will take more time.

Hopefully that helps,

Ken

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#254829 - 12/22/12 12:38 AM Re: Let's Talk PLBs...... [Re: KenK]
Doug_Ritter Offline

Pooh-Bah

Registered: 01/28/01
Posts: 1930
Originally Posted By: KenK
Originally Posted By: spuds
I want it for if truck goes over the hill or stuck in snow storm.

Is snow an issue for these things to work,have to wait for clear weather?

Would this work in a collapsed building or line of sight to sat essential?


I'll make an attempt to answer your questions about how the PLB will operate in poor weather and/or poor light-of-sight conditions.

When a 406 MHz PLB is activated it transmits a signal that identifies the PLB (I assume there is a unique ID code).

If you are in a latitude between 70 degrees north & 70 degrees south that signal will be picked up almost immediately by geostationary (GEO) satellites that are positioned at the equator.

If you are not within that 70 degree latitude area - or marginal - that signal can still be picked up by low-Earth orbiting (LEO) satellites. Because LEO satellites have a more narrow view of the Earth it may take some time for one of them to come into "view" of your PLB signal. This potential time delay is longer at the equator and shorter at the poles - up to 1.5 hours. The maximum delay in the United States is about 1 hour.

It is my understanding that transmission of the PLB signal to the GEO and LEO satellites does not require direct line-of-sight, and will do well even in poor weather. The effect of mountains and buildings in blocking the signal will depend on the type and location of the receiving satellite - your mileage may vary there.

Receiving the PLB signal alone is of limited benefit if the system does not know your location.

There are two methods of identifying the location of the PLB signal: GPS and Doppler. The GPS method requires a clear view of the sky, but the Doppler method is more robust and shouldn't be impacted by weather.

GPS:
If your PLB is equipped with a built-in GPS capability, AND you have a reasonably clear view of the sky, AND the GPS has succeeded in locking in on enough GPS satellites to provide position coordinates, then the PLB transmission will include those position coordinates to both the GEO satellites (potentially instantaneous) and the LEO satellites (may be delayed up to 1.5 hours). The accuracy of the GPS position is within about 400 feet.

Historically GPS has required a fairly clear view of the sky, but in the last few years more advanced GPS chipsets can lock onto GPS satellites even without a direct view of the sky (under vegetation, inside buildings, ...). I'm pretty sure all modern PLBs have those more advanced GPS chipsets.

Doppler:
If your PLB is not equipped with a built-in GPS capability, or you do not have a clear view of the sky, your position can still be determined by the LEO satellites using a Doppler effect - though there can be that delay associated with the LEO satellites. The accuracy of the Doppler position is within 1.2 to 3 miles, but averaging about 1.5 miles.

Note that because the GEO satellites are geostationary there is no Doppler effect - they aren't moving relative to your location, so they cannot find your location using this method.

It seems to me that the +/-1.5 miles area is pretty big, but its far far better than no location information at all. At least they will be looking for you nearby.

DO get a PLB that has an onboard GPS capability.

If you activate the PLB, then you'll want to give it as good a view of the sky as you can. If you're in your vehicle, put it outside. If you're in a collapsed building, put it near a window - or an opening if possible. Getting that GPS position means they'll essentially come right to you. Without that GPS position they'll need to search for you which will take more time.

Hopefully that helps,

Ken


Ken,

You are hereby appointed assistant PLB expert here. :-)

One thing I can add. PLBs are equipped with homing signal on 121.5 MHz. So, when the beacon is located within a couple miles via Doppler, that is quite adequate to be in range of the homing signal and SAR can accurately home into your location from the air or the ground. That's what the homing signal is for.

Beyond that, more and more SAR aircraft (USCG, CAP and Air Force) are now equipped with digital 406 MHz direction finders that can home in on the intermittent, but much stronger (5W), 406 MHz signal. Homing from as far as 120 miles has been seen in real world SAR cases.

Doppler and this dual homing capability is a major advantage that 406 MHz PLBs (and EPIRBs and ELTs) have over alternative distress signaling devices that must have a GPS location to be useful for locating them.


Edited by Doug_Ritter (12/22/12 12:39 AM)
_________________________
Doug Ritter
Editor
Equipped To SurviveŽ
Chairman & Executive Director
Equipped To Survive Foundation
www.KnifeRights.org
www.DougRitter.com

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#254830 - 12/22/12 12:47 AM Re: Let's Talk PLBs...... [Re: Russ]
Glock-A-Roo Offline
Old Hand

Registered: 04/16/03
Posts: 1076
Originally Posted By: Russ
it is also tied in with a paracord lanyard. It doesn't float and in the environment I could use it, the water is very deep, so I keep it firmly attached to something that will float -- me.


I was going to post the same thing. I don't mind that my ResQLink doesn't float because it is always attached with a dummy cord.

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