Experiences with satellite phones?

[Ken Larson]

"Neither spot or plbs or inreach or sat phones work well unless you have a clear view of the sky.”

Just returned from Isle Royal National Park where I use ACR Resqlink™ 406 GPS (PLB-375). Ten 1 sec OK messages were sent, 5 were received properly by the grandchildren's parents. All case I thought I had a clear enough view of the sky. This is NOT the first time I have had issues of less than 50% message completion this device in the past three years. One year the hurricane on the East Coast interfered with ACR message transfer from satellite to receiving station in the state of Maine
I also set ONE 5 sec OK message with coordinates attached that was not received…Houghton County Memorial Airport parking lot, sky clear but many cars (that is the issue according to ACR.)

Jack Ryan
Customer Service Technician
ACR / ARTEX – ACR Electronics, Inc
"The PLB when tested with the optional 406Link Messaging system has to be done during a clear sky with the antenna deployed and no buildings/ metallic objects/ trees/ mountains/ or other radio interference nearby for it to work at its optimum. When performing the self-test and GPS test you have to keep in mind that the signal is only sent out once per self-test/GPS test and if not performed in the best conditions the signal may become corrupt and the satellite may not be able to recognize the Unique Identification Number (UIN) that is encoded and sent with the 406 MHz signal.

[Bob Gross]

There are at least two big problems with this entire discussion. Most of my experience is with GPS reception, and that is on 1.57GHz. However, many of the same issues are present with beacons and sat phones.

1. There is no definition of what is a clear view of the sky.

2. Most users would not know radio frequency interference if it bit them on the butt.

–B.G.–

[Zorg Zumo]

Thanks for helping dispel this myth of the "invincible PLB". Until recently, you couldn't test a PLB, and people just put faith in them like a good luck charm. SPOT's ability to signal has been well known from the beginning, and some people were really put off that sometimes SPOT missed messages. So I think there is a new awakening amongst the outdoor crowd as they come to understand the limitations of these products.

Perhaps Sat phone users were the most savvy as they had to get optimum position to make their call.

[Greg Mihalik]

"Neither spot or plbs or inreach or sat phones work well unless you have a clear view of the sky."

Well, maybe….

From Equipped to Survive:

"We started with a baseline test with a wide open sky, lots of satellites visible, and the Fast Find consistently sent out its GPS location in the first 406 MHz data burst, 50 seconds after deployment.

"We then started to artificially create much more difficult circumstances, using a "space blanket" with metalized lining to block GPS signals down to no more than 3-4 satellites visible and forcing difficult geometry.

"Even under the most difficult circumstances we could create using the blanket, such as at the bottom of a 5-galloon bucket surrounded by the space blanket, it still got a GPS fix consistently within the first 1-2 bursts with a single case of 3 bursts."

If you follow the link there is more, but of course you must be willing to read…

[Jerry Adams]

Nice they're testing it, but I don't care how it works when you put up a space blanket, I won't be doing that.

What about when it's in a canyon or under trees : )

[John S.]

Declaring failure of a PLB to save a life by it's messaging failures is not an accurate assessment.

[Jim Milstein]

In effect, Jerry, the testers were creating an artificial canyon with the bucket and space blanket. The good thing is that this condition is easily repeatable. The bad thing is that it is not a real canyon.

The space blanket wrapped bucket restricts the device's view of the sky to a fairly narrow cone. As they say, this means few satellites and poor geometry (they are all close together). Not a meaningless test.

[Greg Mihalik]

"Space Blackets" are far more opaque to radio signals than a tree canopy.

[BlackHatGuy]

"Space Blackets" are far more opaque to radio signals than a tree canopy."

As are some clothes.

[Jim Milstein]

I'll put my tinfoil hat up against anything from RBH! It also shields me from the emanations of Zorg Zumo.

[Jerry Adams]

I'm not saying the test is invalid

But why put another layer of uncertainty on it, is this adequately simulating canyon or tree cover?

Another good test would be to go under trees and in several different canyons

[Jim Milstein]

Ok, Jerry, but to be valid the study would need to use thousands of locations in hundreds of canyons in all sorts of environments and have solid statistical design. The bucket 'n' blanket test is a pretty good cheap and dirty first draft. Going to a couple of your favorite canyon locations and reporting the results is classic anecdotal evidence. Interesting, but that's all, and arguably no better than the BnB test.

[Jerry Adams]

Did they design their space blank test statistically?

You also need to test with different satellite positions. It varies over the day, and from year to year. I can think of places where my GPS loses lock, but another time it worked.

Probably someone else has tested at some representative locations.

[Bob Gross]

"The space blanket wrapped bucket restricts the device's view of the sky to a fairly narrow cone. As they say, this means few satellites and poor geometry (they are all close together). Not a meaningless test."

I agree. From the GPS receiver world, we used to use a 5-gallon metal bucket that was grounded. Then, we put the GPS receiver antenna on a screw threaded rod in the center. By turning it, we could raise or lower the antenna which would affect the horizon mask angle. In effect, we could selectively block RF interference which tends to approach from the horizon.

—B.G.—

[Jerry Adams]

The devil wants me to say:

"if I wanted my GPS receiver to work in a metal bucket, this would be a very good test"

It's sort of like the Soto test where they put it in ice water – if I wanted my stove to work in ice water, that would be a good test.

[Zorg Zumo]

"Declaring failure of a PLB to save a life by it's messaging failures is not an accurate assessment."

Absolutely correct.

Testing of PLBs is new. ACR ResQLink owners are experiencing message loss and this has been a bit of a shock to PLB aficionados. Negative reviews are popping up on major sites by people who are doubting that their PLB will work when needed. Their doubts reveal that the PLB concept was oversold – hyped a bit too much.

SPOT has been extensively reviewed – it's pro's and con's examined from the beginning.

I'm not giving credence to "doubts", i.e. I don't believe the ACR ResQLink or SPOT are bad products. But I recognize that a lot of people have had their bubbles burst. The "good" from this is that serious purchasers can make a more educated choice on the device that best suits their needs. The "bad" is that some people are not going to buy anything because nothing available is perfect – and the imaginary perfection is the talisman they desire.

[Greg Mihalik]

"Negative reviews are popping up on major sites by people who are doubting that their PLB will work when needed."

Got any references to those reviews?

Got any leads on whether it is just the messaging system that is failing (common with commercially operated SPOT), or it is also the GPS Fix uplink as well.

I, and everyone here, would like to know about any PBL "fix uplink failure". I really don't care about messaging or the infrastructure behind it.

Thanks.

[Zorg Zumo]

Head to the REI site and look up the ACR ResQLink. I think it is a review posted in July/2013 (second one down).

[Greg Mihalik]

Zorg –
I found this statment:

"I tried two self-tests with clear sky view and neither was received by the satellites."

A "self-test" only looks for, and confirms, a lock on the GPS satellites. It does not send a "Help Me" message. Nothing would be Received by any part of the system.

[Edit: If the Messaging was tested that is a different scenario, and as noted on the 406 site, it is only sent Once as a test. In the field it gets repeated.]

And if this single (user incompetent) statement is all you are using to indite PLB functionality I think you need to get a little perspective.

[Zorg Zumo]

Bitter beer?

On this very thread, back on page two, is a very nice writeup by KEN LARSON. Read it please.

Regarding the REI review: This reviewer is an example of the non-technical consumer who is posting their "doubts". Has nothing to do with whether or not their doubts are valid, or whether they were able to read directions – it didn't work for them and they are not happy. That is what "testing" capability has wrought.

[Greg Mihalik]

Zorg,

Bitter? No, just not willing to listen to unfounded innuendo.

Ken is talking about "Messaging" – the "I'm OK" stuff.

That is far different that a PBL GPS uplink process, and in no way reflects on the reliability of the GPS fix uplink process used in Emergency communications.

Your statement that "Negative reviews are popping up on major sites by people who are doubting that their PLB will work when needed…" suggests that the essential function of Emergency Rescue is somehow compromised and is quite stretch from failed messaging.

PBLs have been in place and used successfully for years in the marine and aviation spheres, and now by backcountry hikers.

"Messaging" has not, as you see.

[Zorg Zumo]

I see, so you are saying that the "I'm OK stuff" uses a different radio on the device? See you are trying to be "technical" and I'm pointing out the moderately irrational mindset of users.

I happened to read the down the REI reviews and found another one similar to Ken's. The user expressed his doubts and hope that the device would work when he really needed it. Why? Because he had a high "I'm OK" message failure rate.

People used to buy PLBs and never, ever turn them on. They fully believed that there was some sort of magic with the vaunted cospas-sarsat system. Now that they can do some "testing" (I'm OK messages, etc.), reality is sinking in.

[Greg Mihalik]

zorg –
"…so you are saying that the "I'm OK stuff" uses a different radio on the device?…

Nope. I don't know if it uses the same radio system or not.

What I am saying is that the "Messaging" and the on-the-ground infrastructure behind it is in it's infancy, has never worked reliably, has seen LOTS operator errors, and has a ways to go.

And that the Emergency rescue side of the system is damn near bullet-proof IF you pay just a modicum of attention to how to operate at PBL.

"[People]… fully believed that there was some sort of magic with the vaunted cospas-sarsat system."

cospas-sarsat does work and is reliable. No magic required.

"Now that they can do some "testing" (I'm OK messages, etc.), reality is sinking in."

Testing via "Messaging" has nothing to do with the Emergency side of the system, except to point out that some users think a PBL should work just like their cell phone. And that if the "emergency" side is handled by a commercial operation, like SPOT, all bets are off in terms of reliability (at least from my perspective).

[Zorg Zumo]

"I don't know if it uses the same radio system or not. " – yea it is the same radio.

I'm sure you're right – the infrastructure for the messaging is a work in progress. But I've a feeling that few doubting users understand that.

Personally, I think that the sole reason US customers view cospas-sarsat system as "bulletproof" is the US Coast Guard. Most of the high-profile rescues (i.e. newsworthy) are done by the Coast Guard and their skill level is so high that they rarely fail even in the nastiest of conditions. Off subject but it is easy to be lulled into thinking that all SAR is like the the CG.

[Ken Larson]

Sent SIX 1 sec tests in different "clear sky" openings:

Test #1 1150 hrs POSITIVE TEST

Test #1 Test location on the ground

Test #2 1153 hrs NEGATIVE TEST

Test #3 1157 hrs NEGATIVE TEST

Test #4 1213 hrs (waters edge of a bayou)POSTIVE TEST

TEST #4 Test location on the ground

Test #5 1215 hrs NEGATIVE TEST

Test #6 1217 hrs NEGATIVE TEST

Operational Definition of "clear sky"…….no immediate obstacles in vicinity of outgoing signal for a POSITIVE TEST.

[Author]

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