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Old 19-05-2015, 09:55   #136
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Re: Are EPIRBs dead?

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Originally Posted by brianb00 View Post
You are not serious ? Please don't leave the impression that HF radio is a modern solution to SAR. A erupting sunspot routinely renders HF useless for any distance on all frequencies likely to be aboard a small boat.

"These systems are fragile" - again I will state the world is very heavily invested in EPIRB tech. There are three full satellite clusters monitoring the frequency and auto linked to world wide ground stations, and that is just the U.S. investment ! Geostationary, Mid altitude sats (MEO), and low earth orbit (LEO), make the coverage bullet proof. The hand held units are made to very high standards, and the USCG is committed to a 95% response rate within 4 minutes of a ping from an EPIRB/PLB. If you push the little red button you can bet the USCG will react immediately with the highest priority. Did you know that in the San Francisco area they have rotors spinning on helo's within 7 min of a received EPIRB signal ?

As for Iridium - great system - and if it wasn't for the US Gov't investing heavily via the state department it would not exist. THat was an example of private enterprise not understanding their own market, a total fail.

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All these systems have their strengths and weaknesses.

I think that Hello Sailor has given an excellent summary of the strengths of HF radio. No one argues that HF radio has no weaknesses as a distress signalling system.

I would only quibble with the statement that HF radio is not a "modern solution to SAR". I think HF DSC definitely is a modern solution, and a robust one. And it's firmly embedded in GMDSS. HF radio is a very powerful and versatile comms tool with lots and lots of different modes of usage.

The biggest minus of HF radio for distress signalling, in my opinion, is not sunspots, but the fact that it won't work at all with the mast down or in the life raft. Or without power (although if you have a GMDSS-compliant installation, your radio will have a separate battery).
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Old 19-05-2015, 11:14   #137
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Re: Are EPIRBs dead?

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Originally Posted by Dockhead View Post

The biggest minus of HF radio for distress signalling, in my opinion, is not sunspots, but the fact that it won't work at all with the mast down or in the life raft. Or without power (although if you have a GMDSS-compliant installation, your radio will have a separate battery).

Back in my early days at sea, we used to have a lifeboat radio on the ship, designed to be used in a lifeboat or raft, believe it or not, it was hand cranked, no batteries required, and operated on the 2182kHz for voice or 500kHz for telegraphy.
I was quite happy to see it replaced by the EPIRB.

http://www.aberdeenquest.com/Artwork/LifeboatRadio.asp
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Old 19-05-2015, 11:15   #138
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Re: Are EPIRBs dead?

Great things are happening in lifesaving electronics. The cost of EPIRBS has really come down and their capabilities have significantly increased. This makes them an excellent value. My first EPIRB, purchased in 1988, was over $1K and was stone age technology compared to what is available now for less than 1/2 the price.

I also have a SPOT messager. When cruising we send an "OK" message each evening to our Float Plan Monitor (my daughter, who worries about us) and to several others. They enjoy watching our progress and getting daily satellite images on their email of our location. We have been doing mostly coastal and inland river cruising lately, where we often have no cell coverage, and the SPOT has worked every time. Due to some unfortunate incidents, SPOT GEOS SAR, the emergency portion of their service, is likely learning how to make their service more bullet-proof as well.

If you are like us, we spend a lot on our hobby. In the big picture, the cost of EPIRBS, SPOT and DeLorme equipment is so low compared to their benefits everyone can justify having both.
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Old 19-05-2015, 11:27   #139
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Re: Are EPIRBs dead?

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Originally Posted by Dockhead View Post
You make the wrong conclusion.

Modern EPIRBS emit two signals: One burst signal at 406 mhz every approximately 50 seconds (pseudo randomized to vary a little from that in order to prevent accidentally simultaneous bursts from different EPIRBs), and one continuous homing signal at 121.5 mhz.

The 406 mhz signal contains a digital burst, but also contains a short emission of an unmodulated carrier, so it can also be homed on, which the satellites also do besides receiving the digital signal with position data. The old 121.5 hz analogue satellite system did nothing but home -- the old EPIRB signals contained no digital information.

The 406 mhz signal is stronger (5 watts), but is emitted for only half a second at a time. Some later RDF equipment (like the Rockwell-Collins DF500) can home on it. But many SAR aircraft, maybe most of them, cannot home on 406 signals. Typical equipment is the Becker SAR-DF 517. In any case, the intermittent 406 mhz burst signal is not intended for homing in the last miles. That is what the continuous 121.5 mhz signal is for. ALL SAR aircraft can home on the 121.5 mhz homing signal, and in fact, you can even home on it with an ordinary VHF airband radio, if you know how to do it.


You know what "homing" is, right? It's a technique about as old as radio. If you receive a radio signal and have a directional antenna, you can determine the bearing to the transmitter. If two or more receivers do this, you can triangulate two or more bearings to get a position. Even if your antenna is not directional, you can follow the signal as it gets stronger or weaker, if your receiver is mobile.


So in short, the continuous 121.5 mhz homing signal emitted by all modern EPIRBs and PLBs is the primary means of locating the casualty in the last few miles of the rescue operation. Not the 406 mhz signal, which is primarily used for transmission of bursts of digital information to get out the distress signal to the satellites, and to provide an initial position to get the rescue operation started.


I find your condescending tone extremely annoying, especially since I'm an ESM operator, maintenance technician and former instructor of a $1.4M RDF system. That's like me asking you if you know how to breathe.

If you don't believe that the USCG homes in on the 406 MHz signal instead of the 121.5 MHz signal, take that up with the USCG. It says it right on their website, if you bothered to read the quote.

Aside from increased signal strength, it's a well known fact that DF bearing accuracy dramatically increases at higher frequencies. The shorter wavelengths are easier to resolve.

BTW, according to Becker, the SAR-DF 517 has the following frequency capabilities:

Quote:
Receiving frequencies: Emergency mode
(or see type plate for 121.500 MHz (VHF)
special customer options) 156.800 MHz (Maritime, Channel 16)
243.000 MHz (UHF)
406.025 MHz (Cospas / Sarsat)
Trainings mode
118.000 ....122.975 MHz
156.000 .....157.975 MHz
240.000 .....245.975 MHz
400.000 .....409.975 MHz
Perhaps they're also mistaken about their own equipment.
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Old 19-05-2015, 11:45   #140
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Re: Are EPIRBs dead?

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Originally Posted by socaldmax View Post
I find your condescending tone extremely annoying, especially since I'm an ESM operator, maintenance technician and former instructor of a $1.4M RDF system. That's like me asking you if you know how to breathe.

If you don't believe that the USCG homes in on the 406 MHz signal instead of the 121.5 MHz signal, take that up with the USCG. It says it right on their website, if you bothered to read the quote.

Aside from increased signal strength, it's a well known fact that DF bearing accuracy dramatically increases at higher frequencies. The shorter wavelengths are easier to resolve.

BTW, according to Becker, the SAR-DF 517 has the following frequency capabilities:



Perhaps they're also mistaken about their own equipment.
Sorry, no condescension was intended.

My intention was merely to correct the impression which I think was being spread that 121.5 mhz homing went out when COSPAS/SARSAT stopped processing 121.5 mhz beacons. It is a true fact that 121.5 mhz homing is still used, and is still the primary means of directing SAR teams the last miles of a rescue operation.

No one argues that 406 mhz signals can also be homed in on. Any radio signal can be homed in on. But the 406 mhz burst signals are not primarily intended for this purpose. There are advantages for homing at long distances, but with modern EPIRBs the GPS position data transmitted by burst is used for this, not homing. You need RDF homing just for the last miles, and this is what 121.5 mhz homing is intended for in modern equipment.

And for the record, the Becker SAR-DF 517 does not home on most of the 406 mhz EPIRB signals, see: http://www.capmembers.com/media/cms/...24A42EC69E.pdf


"Newer 406 MHz Distress Beacons are now being sold that transmit on 406 MHz channels that are not detectable by CAP’s current airborne direction finder, the Becker SAR-DF 517. That device is only capable of detecting and processing 2 of the eighteen 406 MHz Distress Beacon Channels (excluding the 406.022 MHz Reference Channel)."


I'm not trying to put anyone down; just trying to keep the record straight and dispel misconceptions, many of which have been spread in this thread. A lot of people read and learn from these threads.
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Old 19-05-2015, 11:47   #141
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Re: Are EPIRBs dead?

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Originally Posted by nigel1 View Post
Socaldmax may be on to something here

Lifted this paragraph from a USCG document



That would suggest USCG SAR aircraft have the ability to home on 406Mhz.

I would hazard a guess that 121.5 homing signal is retained as most aircraft can receive this frequency on a direction finder, whereas only a few dedicated aircraft can home on the 406 signal.

What we need is a USCG pilot to step in and either confirm or deny.
Thanks for that.

I'm just amazed that someone would argue with the quote I lifted from the USCG NAVCEN website, which should be pretty much gospel in terms of what the CG does or doesn't do.

As a matter of RDF design, as transmitter frequency rises, wavelength decreases. Smaller wavelengths are more accurate to DF due to antenna design constraints and propagation (similar to treble being highly directional while bass drum appears omni directional.)

Mobile RDF units utilize an antenna array inside of the antenna housing, high speed switching is used to compare/contrast amplitude differences between different antennas at lower frequencies and phase difference at higher frequencies. In the case of my equipment, the frequency crossover is still a secret design parameter.

Due to space and weight reasons, aircraft can't carry an antenna array that is really accurate down to lower frequencies. Sure, they can get you kinda close, but if your contact is 100+ mi away, +/- 5 or 10 degrees is still a lot of ocean.

121.5 MHz isn't too hard to DF, but 406 MHz will give you tighter bearing accuracy, and the much greater signal strength really helps with initial acquisition. Even if both signals were equal strength, the 406 MHz signal is inherently the superior signal to DF, just based on it's frequency.
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Old 19-05-2015, 11:58   #142
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Re: Are EPIRBs dead?

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Originally Posted by Cal31 View Post
Great things are happening in lifesaving electronics. The cost of EPIRBS has really come down and their capabilities have significantly increased. This makes them an excellent value. My first EPIRB, purchased in 1988, was over $1K and was stone age technology compared to what is available now for less than 1/2 the price.

I also have a SPOT messager. When cruising we send an "OK" message each evening to our Float Plan Monitor (my daughter, who worries about us) and to several others. They enjoy watching our progress and getting daily satellite images on their email of our location. We have been doing mostly coastal and inland river cruising lately, where we often have no cell coverage, and the SPOT has worked every time. Due to some unfortunate incidents, SPOT GEOS SAR, the emergency portion of their service, is likely learning how to make their service more bullet-proof as well.

If you are like us, we spend a lot on our hobby. In the big picture, the cost of EPIRBS, SPOT and DeLorme equipment is so low compared to their benefits everyone can justify having both.
I agree!

This is also why I'm of the opinion that if one doesn't have an HF system installed already and is contemplating spending the $5,000 to get the whole enchilada (transceiver, tuner, Pactor modem, antenna, counterpoise) then one should investigate how much more equipment you can get for much less - GPIRBs, SPOT or Inreach, handheld VHF, VHF with DSC, AIS, RADAR (good for avoiding squalls as well as traffic) etc, etc.

One can listen to the maritime HF nets with a $150-300 receiver (PL-880 or Eton E1) but to talk to anyone, you'll need a marine HF radio at $1900 plus the tuner, antenna, counterpoise, which is several hundred more.
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Old 19-05-2015, 12:05   #143
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Re: Are EPIRBs dead?

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Originally Posted by Dockhead View Post
Sorry, no condescension was intended.

My intention was merely to correct the impression which I think was being spread that 121.5 mhz homing went out when COSPAS/SARSAT stopped processing 121.5 mhz beacons. It is a true fact that 121.5 mhz homing is still used, and is still the primary means of directing SAR teams the last miles of a rescue operation.

No one argues that 406 mhz signals can also be homed in on. Any radio signal can be homed in on. But the 406 mhz burst signals are not primarily intended for this purpose. There are advantages for homing at long distances, but with modern EPIRBs the GPS position data transmitted by burst is used for this, not homing. You need RDF homing just for the last miles, and this is what 121.5 mhz homing is intended for in modern equipment.

And for the record, the Becker SAR-DF 517 does not home on most of the 406 mhz EPIRB signals, see: http://www.capmembers.com/media/cms/...24A42EC69E.pdf


"Newer 406 MHz Distress Beacons are now being sold that transmit on 406 MHz channels that are not detectable by CAPís current airborne direction finder, the Becker SAR-DF 517. That device is only capable of detecting and processing 2 of the eighteen 406 MHz Distress Beacon Channels (excluding the 406.022 MHz Reference Channel)."


I'm not trying to put anyone down; just trying to keep the record straight and dispel misconceptions, many of which have been spread in this thread. A lot of people read and learn from these threads.
I apologize for the misinformation on the SAR-DF 517, their specs in their manual covered the 406 MHz frequency, so I wrongly assumed it could receive those signals.

That's the difference between less expensive, specialized RDF units vs more expensive, more accurate, wider frequency range, full band units designed primarily for ESM vs just SAR.

I also believe we must strive to be as accurate as possible, thus my quoting material directly from the USCG website as to their homing in on the 406 MHz signal. That's not my assertion, it's theirs. You're not arguing with me, but with what's posted on the USCG site.
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Old 19-05-2015, 12:16   #144
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Re: Are EPIRBs dead?

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Originally Posted by socaldmax View Post
I apologize for the misinformation on the SAR-DF 517, their specs in their manual covered the 406 MHz frequency, so I wrongly assumed it could receive those signals.

That's the difference between less expensive, specialized RDF units vs more expensive, more accurate, wider frequency range, full band units designed primarily for ESM vs just SAR.

I also believe we must strive to be as accurate as possible, thus my quoting material directly from the USCG website as to their homing in on the 406 MHz signal. That's not my assertion, it's theirs. You're not arguing with me, but with what's posted on the USCG site.
I'm actually not arguing either with you or with the Coast Guard. Certainly homing is done on 406 signals; I never disagreed with that.

The only thing I was arguing against was the impression -- and maybe you didn't intend it -- that 121.5 mhz homing is obsolete. It's not obsolete; it's primary, and it's built into all modern EPIRB and PLB sets. That was really my main point. It doesn't look like many USCG SAR assets are able to home in on 406 at all, although that will change gradually as new equipment is introduced.

You've added useful information about the technical advantages of higher frequency homing on 406. 406mhz signals are also higher power, even if they are intermittent. I am guessing -- and it would be useful to hear from a USCG SAR pilot -- that this would be really needed when rescuing someone who was dumb enough to buy a 406 mhz EPIRB without GPS. There the longer range would be helpful since you won't get an exact position from the satellites.
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Old 19-05-2015, 15:15   #145
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Re: Are EPIRBs dead?

Brian-
I don't say that HF is perfect any system has problems. Like, needing ship's power to operate and an intact and upright antenna which may have been lost when the backstay snapped and mast went down.


I'm not aware that the UPS routinely uses three different satellite constellations for SAR reception, this is the first I've heard of it. And while that just goes to show the point (that a single civilian company or product isn't as robust as EPIRB) it is still a fragile system. There are many high-ranking folks involved with "Space Command" who stay awake at night wondering whether we'll make things more robust, before some rogue state, solar flare, or simple accident renders most of our orbital assets into orbital trash. In one shot.


Of course, they can't even talk about that, since it is rightfully classified information. But from what has been said, and simple physics, there's a lot to worry about. In terrestrial disasters, a lot of information still gets carried by ham radio on HF, despite the deployment of satellite ground stations. Simply because those immediately run out of capacity and there's always more than they can handle. And that's under the best of circumstances. High tech is great--until it needs those elusive high tech repair solutions.
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Old 19-05-2015, 16:25   #146
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Re: Are EPIRBs dead?

I think the problem with HF is the difficulty getting up to speed for the average, non-techy layman. I had an Icom M-802 professionally installed on my boat. Nothing but static except one night anchored out in the Bahamas I got Puerto Rico clear as a bell (800 nm per the GPS as I recall). Otherwise, it's been all static. Had two techy's onboard testing the system, incl. CF's own Bill Trayfors. Everything checked out installation-wise both times, but still nothing but static for me. Then I recently discovered -- thanks to CF's Capt. John & his generous threads & youTubes -- that my professionally installed M802 was never hooked up to GPS, that a separate antenna is required for DSC, and that the manual has incorrect info about how to utilize the otherwise worthwhile sounding DSC potential. Then it was Capt. Marti Brown's Idi-Yacht's guide, and another book advertising itself as the equivalent of the moron's guide. Still static. I know, I know, I need to quit being an idiot and a moron, move the boat away from the marina, drop the hook, and sit there until I learn it! My only point is that, compared to a satphone, Epirbs, and just about every other onboard system I've managed -- despite myself -- to get on top of over the years, the HF radio still sits almost as unused as my plastic sextant. I don't think I'm alone with this experience, and wish my HF radio and its manual were more user friendly. I'll stick with it as I agree it has great potential, but it wouldn't surprise me, given the alternatives, if many are deterred for the reasons I've described.
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Old 19-05-2015, 21:24   #147
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Re: Are EPIRBs dead?

". I don't think I'm alone with this experience, and wish my HF radio and its manual were more user friendly. "
You are not alone. In fact, this is the reason that early PC "mice" often had ten or more buttons (to click on functions while on a tablet) and the specific reason that Apple mice have and had ONLY ONE BUTTON.


Dude, three buttons? That's like, so confusing.(G)


But there it is, proof that you are not the only one.


You think a young Bill Shatner is the only one who ever saw gremlins tearing the engine off an airplane? Someday, someone, will figure out why your SSB is so hostile. It will be a Homer Simpson Moment, when everyone goes "D'oh!" because it is so obvious, yet subtle.
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Old 19-05-2015, 21:28   #148
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Re: Are EPIRBs dead?

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I think the problem with HF is the difficulty getting up to speed for the average, non-techy layman. I had an Icom M-802 professionally installed on my boat. Nothing but static except one night anchored out in the Bahamas I got Puerto Rico clear as a bell (800 nm per the GPS as I recall).
I don't know where in the world you are but there should be HF signals that you can receive. If you want some help send me a PM. I have an ancient HF SSB and can receive lots of stations as well as send and receive email and capture weather fax images.
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Old 19-05-2015, 22:49   #149
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Re: Are EPIRBs dead?

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". I don't think I'm alone with this experience, and wish my HF radio and its manual were more user friendly. "
You are not alone. In fact, this is the reason that early PC "mice" often had ten or more buttons (to click on functions while on a tablet) and the specific reason that Apple mice have and had ONLY ONE BUTTON.


Dude, three buttons? That's like, so confusing.(G)


But there it is, proof that you are not the only one.


You think a young Bill Shatner is the only one who ever saw gremlins tearing the engine off an airplane? Someday, someone, will figure out why your SSB is so hostile. It will be a Homer Simpson Moment, when everyone goes "D'oh!" because it is so obvious, yet subtle.
Not yet convinced it's the SSB that's so hostile, but rather the guy sitting in front of it turning the dials & pushing the buttons!
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Old 19-05-2015, 23:01   #150
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Re: Are EPIRBs dead?

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I don't know where in the world you are but there should be HF signals that you can receive. If you want some help send me a PM. I have an ancient HF SSB and can receive lots of stations as well as send and receive email and capture weather fax images.
Thanks for the offer. I'm away from the boat for several more weeks but I may take you up on that when I return. The boat is in the Norfolk, VA these days in an area with a high concentration of marinas. I've been told this might be part of the problem. The grounding is to the solid bronze rudder post which I've always been a bit dubious about, although a couple of qualified guys have tested it as OK as already mentioned. The other problem that has been suggested is that the M802 presets don't properly line up with the proper frequency which can apparently change over time. I've played with that quite a bit with no success. You'd think they'd at least be close enough to fine tune your way in. Ah well, probably enough thread drift on this one.
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