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Old 25-07-2014, 22:13   #46
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Re: EPIRB Thoughts?

Lower current drain is a consideration, to be sure. But these days, with radio transmitters? The input power is based on the output power. The GPS power drain was minimal long ago. (Cell phone chips & wristwatch chips.)

So unless they've got fusion reactors and quantum transmitters in there, I can't see that the power drain is THAT much different from any other unit. Unless the whole industry is still using Soviet surplus vacuum tubes. (Which would be a really good idea, if there was a solar storm that wiped out all the electronics on the earth but somehow missed the GPS and SAR satellites hiding on the dark side.(G)

I've just found that when sales & marketing for any INCREDIBLE! NEW! IMPROVED! UNIQUE! product don't mention what's really changed? It has only been something mundane.

Or as we say in the colonies, "Show me, I'm from Missouri."
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Old 26-07-2014, 03:02   #47
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Re: EPIRB Thoughts?

Wotname:

No, you're not the only sailboatie participating: A 64pilot's one too.

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Old 26-07-2014, 03:44   #48
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Re: EPIRB Thoughts?

And now there are three
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Old 26-07-2014, 04:04   #49
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Re: EPIRB Thoughts?

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Originally Posted by hellosailor View Post
Lower current drain is a consideration, to be sure. But these days, with radio transmitters? The input power is based on the output power. The GPS power drain was minimal long ago. (Cell phone chips & wristwatch chips.)

So unless they've got fusion reactors and quantum transmitters in there, I can't see that the power drain is THAT much different from any other unit. Unless the whole industry is still using Soviet surplus vacuum tubes. (Which would be a really good idea, if there was a solar storm that wiped out all the electronics on the earth but somehow missed the GPS and SAR satellites hiding on the dark side.(G)

I've just found that when sales & marketing for any INCREDIBLE! NEW! IMPROVED! UNIQUE! product don't mention what's really changed? It has only been something mundane.

Or as we say in the colonies, "Show me, I'm from Missouri."
Well you do have a point (several in fact); the main being "you can't trust marketing wallas". I gotta agree with you

Yes, output power is a function input power - can't escape fundamental electrical concepts. Mitigating factors are reducing wasted power in the transmitter (i.e. improving Tx efficiency) and remembering an EPRIB only transmits for less than 1% of its operating cycle on the high power (5W) transmitter (406). That is about 400 or 500 milliseconds every 50 to 60 seconds. Any power saved in the other 99% of the cycle is very worthwhile.

The low power transmitter (121.5) is of course, continuos but transmitting only 25 milliwatts so it isn't such a big deal.
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Old 26-07-2014, 05:14   #50
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Re: EPIRB Thoughts?

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On my ACR the entire pack unplugs, and a new pack (of 3 "D" size lithium cells) complete with the same connector can be bought for under $60. Plug, unplug.


Did you happen to take a photo of it?
If so could you post it for us please?

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Old 26-07-2014, 06:23   #51
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Re: EPIRB Thoughts?

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The low power transmitter (121.5) is of course, continuos but transmitting only 25 milliwatts so it isn't such a big deal.
Interesting. I assume the old 121.5 EPIRBs transmitted the 121.5 homing signal at a higher power level. Also their antennae are presumably optimised to this frequency rather than 406MHz.

The reason I raise this point, is that many of us have a bunch of old 121.5MHz EPIRBs lying around. While these are in no way, shape or form a substitute for a 406MHz EPIRB, I wonder if they would give a better homing signal if deployed at the same time as a 406 MHz unit, at least for those units without a GPS equipped EPIRB.
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Old 26-07-2014, 09:00   #52
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Re: EPIRB Thoughts?

The main difference between an EPIRB and a PLB is that EPIRBs are designed to signal maritime distress, while PLBs were originally designed for land-based applications. A traditional EPIRB is mounted to your vessel, and will generate a distress signal automatically if immersed in water, if it is a Category I EPIRB, or when you manually flip the switch, if it is a Category II EPIRB. They are mandatory on commercial vessels though a good idea for pleasure vessels.

When determining which emergency beacon to purchase, keep in mind that some type of beacon is better than nothing. It's not a "should I buy" scenario, but a "which one should I buy?" because every boater should have either an EPIRB or a PLB. In some cases, it's not a bad idea to have both. Boats sink or capsize and people fall overboard even with the best planning, boating skill and experience in the world.

I have both EPIRB and PLB's on board as well as a (MOB) Man Over Board system. I recently ordered my new EPIRB from http://landandseaoutfiters.com I believe they carry manufacture replacement batteries as well.

Hope this was helpful.
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Old 26-07-2014, 17:45   #53
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Re: EPIRB Thoughts?

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Originally Posted by noelex 77 View Post
Interesting. I assume the old 121.5 EPIRBs transmitted the 121.5 homing signal at a higher power level. Also their antennae are presumably optimised to this frequency rather than 406MHz.

The reason I raise this point, is that many of us have a bunch of old 121.5MHz EPIRBs lying around. While these are in no way, shape or form a substitute for a 406MHz EPIRB, I wonder if they would give a better homing signal if deployed at the same time as a 406 MHz unit, at least for those units without a GPS equipped EPIRB.
Careful my friend, you are comparing apples with oranges; unintentionally no doubt, due to my less than perfect explanation.

The lower power 121.5 transmitter (at 25 milliwatts) that I referred to a post or so back was the homing aspect of the COPAS SARSAT 406 EPRIB. As you know, all the 406 beacons transmit on 406 and 121.5. In a 406 beacon, the 121.5 transmitter is a analogue AM modulated continuos carrier wave and usually set at 25 milliwatts while the 406 transmitter transmits a 5 watt pulse of digital data of about half a second about every minute. I am not privy to how all different makes and models achieve these parameters and presumably current generation units use a pseudo analogue AM carrier for 121.5. Of course, how they do it doesn't really concern the end user, but it can affect current drain and therefore battery size.

The older discontinued 121.5 & 121.5 / 243 beacons you might still have lying around all used a 100+ milliwatt transmitter (AM continuos CW) so were much more powerful as far as homing ability went. Their frequency stability was something less than perfect although the beacons of very last generation of that era weren't too bad.

So yes, an old beacons would provide some homing assistance but to my mind, this would be a non event. Even with a non GPS EPRIB, doppler shift location will be better than 5 Km and I note that some (many?) are quoting 2 Km thus radically reducing a homing search area. Additionally more and more SAR aircraft and some marine SAR vessels are fitted with 406 Direction Finding equipment. In recent years I have installed more 406 / 121.5 DF units than older style 121.5 DF units. Presumably USA and western Europe / UK are far ahead of Australia in the fitting of 406 DF receivers.
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Old 26-07-2014, 17:48   #54
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Re: EPIRB Thoughts?

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Originally Posted by fishhunter View Post
The main difference between an EPIRB and a PLB is that EPIRBs are designed to signal maritime distress, while PLBs were originally designed for land-based applications. A traditional EPIRB is mounted to your vessel, and will generate a distress signal automatically if immersed in water, if it is a Category I EPIRB, or when you manually flip the switch, if it is a Category II EPIRB. They are mandatory on commercial vessels though a good idea for pleasure vessels.

When determining which emergency beacon to purchase, keep in mind that some type of beacon is better than nothing. It's not a "should I buy" scenario, but a "which one should I buy?" because every boater should have either an EPIRB or a PLB. In some cases, it's not a bad idea to have both. Boats sink or capsize and people fall overboard even with the best planning, boating skill and experience in the world.

I have both EPIRB and PLB's on board as well as a (MOB) Man Over Board system. I recently ordered my new EPIRB from http://landandseaoutfiters.com I believe they carry manufacture replacement batteries as well.

Hope this was helpful.
Welcome aboard Fishhunter, nice first post - if only 'cause I agree .

Anyway, it is good to have you onboard (and I trust you will find CF helpful in finding fish )
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Old 27-07-2014, 00:39   #55
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Re: EPIRB Thoughts?

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So yes, an old beacons would provide some homing assistance but to my mind, this would be a non event.
I understand we are only talking about the 121.5 MHz signal not the primary 406 MHz signal which is the only one the satellite will respond to.

However I have 4x121.5 MHz EPIRBs on board I keep meaning to dispose of them, but they take up very little room and I wonder if they are of any use. I have one attached to my danboy.

I understood the new EPIRBs transmitted on 121.5 as well, but was not aware until your post that it was at a lower power level than the older units.

Do aviation still listen for an alert 121.5 MHz? Is there any chance a commercial plane flying overhead would pick up a 121.5 signal like they used to even though the satellite response to the old units has been turned off?.

The bottom line is there are point in an emergancy situation of activating the 121.5 MHz units as well? Could it do any harm?
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Old 27-07-2014, 01:11   #56
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At the risk of being boring and repetitive - PLBs have another huge plus compared to EPIRBs: you are much less likely to forget or fail to take it with you if the SHTF. I keep my ResQLink lanyarded in my lifejacket, so always on my person.
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Old 27-07-2014, 01:29   #57
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Re: EPIRB Thoughts?

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The bottom line is there are point in an emergancy situation of activating the 121.5 MHz units as well? Could it do any harm?
Probably not, but if you had a 406/121.5 MHz unit why bother firing off the old 121.5 MHz units ?

I guess you could delay setting them off until the 406/121.5 MHz died in the hope search aircraft could still home in on you, but it's extremely rare (if not unheard of these days) that you, or more correctly the EPIRB, have not already been located well before the EPIRB stops transmitting......

I'm not sure if commercial aircraft are actively still monitoring 121.5 MHz, but I do know if an 406 EPIRB is activated in the area they are transiting they are requested to monitor 121.5 MHz.....
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Old 27-07-2014, 02:17   #58
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Re: EPIRB Thoughts?

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..........
Do aviation still listen for an alert 121.5 MHz? Is there any chance a commercial plane flying overhead would pick up a 121.5 signal like they used to even though the satellite response to the old units has been turned off?.
I'm told that some intentional carriers still monitor 121.5 as part of their SOP but can't vouch for this a fact. I do know that old school GA commercial pilots in Oz do it routinely and some younger GA pilots do it occasionally so they can feel they are part of the "old school in club". There must be some USA / UK pilots here who can confirm what happens elsewhere .

AirServices still monitor 121.5 at manned control towers in Oz and consider a 121.5 transmission as genuine Mayday.

121.5 remains an international aviation distress frequency and can be used for voice Mayday calls.


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...The bottom line is there are point in an emergancy situation of activating the 121.5 MHz units as well? Could it do any harm?
Dunno but there is no regulation that prevents it AFAIK. The use of 121.5 should fall under "you can use any frequency you have access to to transmit an emergency call" clause of the ITU regulations.
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Old 27-07-2014, 17:36   #59
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Re: EPIRB Thoughts?

MarkJ-
Sorry, no photo. Sent one by email to confirm it was right when I was replacing it, didn't keep any copy. The connector looked very much like the standard one used in every home wireless handset, typically attached to 2 or 3 AA cells as sold at every Radio Shack. There must be a name for those connectors, I plead blissful ignorance. I think all the RC packs use them as well.

Noelex-
I suspect that anyone, civilian or otherwise, who still has the capability of listening for 121.5 is still doing so on the theory that "it never hurts" and with digital scanners, it costs nothing to monitor the frequency.
If SAR is coming looking for you, they will pick up that obsolete 100mW signal further out than the new 25mW signal. So it definitely couldn't hurt to keep it. Got four of em? And each has what, a 24 hour transmitter time? OK, crack off one when you think someone might here it, and then 24 hours later, crack off the next.
At that price...you know, you could always wed it to a PVC pipe and a sleeve of D cells and make battery replacement cheap too.(G)

Folks who think emergency signals can only be maintained by highly trained, highly authorized, gen-you-whine certified manufacturers, may wish to check COLREGS and ask themselves, who is authorized to repack and recertify those 55 gallon drums of burning material? Or those guns being fired every minute?

In the interest of full disclosure, I should hastily point out that I am authorized to repack 55 gallon drums with shredded tire rubber and combustible jelly by all major manufacturers. But since I'm not a commercial forum member, I don't advertise that service here.(VBG)
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Old 27-07-2014, 17:56   #60
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EPIRB Thoughts?

As of Feb 1 2009 121.5 and 243.0 are no longer being monitored by COMPASS / SARSAT (hope I got the spelling correct)
121.5 is civilian emergency freq (VHF) 243.0 military (UHF). Trivia but 121.5 is exactly 1/2 of 243.0
Anyway the 121.5 signal can be DF'd and I assume only use for it now in a EPIRB?

I wouldn't bother with a 121.5 ELT, save that space and weight for a cup of water or something else.

Be neat though if you had a handheld VHF and could talk to the rescue folks, All military UHF radios were tuned to "guard" freq as well as of course the freq you had in the radio so everyone was listening to 243.0, but never seen a civilian radio that did that.
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