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ACK E-04 ELT


Fritz1

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Finished annual yesterday and tested ACK E-04 ELT, dead, only one year old, had replaced dead one last year, tested old and newer ELT battery, plenty of power, scratched my head, called ACK in Santa Clara, first thing the technician asked me was: did you hook up a portable antenna for the test? yes we did, A&P removed ELT, hooked up portable antenna and performed test of g-switch. ACK technician stated that this blows an amplifier and pointed out that it was stated on the unit not to hook up portable antenna, not written on my old unit, not explicitly stated in manual that this will blow amp, felt great relief, ordered another unit from Spruce since I need bird back in the air and will have the two blown units repaired at ACK. Bottom line: do not hook up portable antenna to ACK E-04 ELT to test the g-switch since this will damage an amp! B)

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It states in the ACK manual not to hook up an antenna for testing the g-switch but it does not state in the manual that hooking up an antenna will damage the transmitter, I just spoke to my A&P, he most likely has blown the ELT in his Baron doing the same thing

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It sounds backwards, actually.    Activating some transmitters without a load (e.g., an antenna) can damage the Power Amplifier in the radio.   If there's an antenna or cable of the proper impedance connected it shouldn't be able to tell one from another.   If there's nothing connected, then it's not unusual to expect damage if the transmitter is activated.

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7 minutes ago, EricJ said:

It sounds backwards, actually.    Activating some transmitters without a load (e.g., an antenna) can damage the Power Amplifier in the radio.   If there's an antenna or cable of the proper impedance connected it shouldn't be able to tell one from another.   If there's nothing connected, then it's not unusual to expect damage if the transmitter is activated.

EXACTLY!

This sounds extremely weird...if a 'portable' antenna is of the proper impedance the final amp shouldn't know the difference!

 

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This is interesting. The manual (Rev 1.08) I downloaded when I purchased the airplane in 2018 with a recently installed ACK E-04 does not mention this. I just checked the current manual (Rev 1.12) and it states in the antenna installation section and in the periodic maintenance section in red bold type not to connect a non-approved antenna.

I guess it is a reminder to keep documentation up to date and read it before performing even simple maintenance. 

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10 minutes ago, EricJ said:

It sounds backwards, actually.    Activating some transmitters without a load (e.g., an antenna) can damage the Power Amplifier in the radio.   If there's an antenna or cable of the proper impedance connected it shouldn't be able to tell one from another.   If there's nothing connected, then it's not unusual to expect damage if the transmitter is activated.

This is the kind of thing that gets me in trouble all the time. Being an engineer, I think I understand stuff. The latest manual says it damages the 406 MHz transmitter. Maybe it's because the rubber duckies are tuned for the VHF communications band. Someone who really cares could call ACK and ask them. But this is Mooneyspace, so I expect that there will be several pages of speculation plus a few pages of posts about how this is a terrible design and then a few outraged folks that think they should all be recalled.:)

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18 minutes ago, PT20J said:

This is the kind of thing that gets me in trouble all the time. Being an engineer, I think I understand stuff. The latest manual says it damages the 406 MHz transmitter. Maybe it's because the rubber duckies are tuned for the VHF communications band. Someone who really cares could call ACK and ask them. But this is Mooneyspace, so I expect that there will be several pages of speculation plus a few pages of posts about how this is a terrible design and then a few outraged folks that think they should all be recalled.:)

That could be.   Antennas for many portable transceivers cover both VHF and UHF, but if somebody stuck a VHF-only antenna on there the impedance at UHF may be high enough to damage the Power Amplifier for 406 MHz (assuming it's separate, which is entirely possible).    Usually testing for annual is just done at VHF though, by listening on a comm radio or handheld, so it's harder to detect if the 406 MHz amp got blitzed and not the VHF.

Edit:  Or maybe the reflected power from the UHF PA also nukes the VHF amp if there's insufficient load at UHF.   I wonder if that's what's happening.

 

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1 hour ago, Fritz1 said:

It states in the ACK manual not to hook up an antenna for testing the g-switch

Excuse me, it says what??????   I find this suspicious!  You never transmit without an antenna/load or you very well may burn out the transmitter.   And does the manual call for a specific load for the antenna, which I guess their antenna provides?

 

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17 minutes ago, PeteMc said:

Excuse me, it says what??????   I find this suspicious!  You never transmit without an antenna/load or you very well may burn out the transmitter.   And does the manual call for a specific load for the antenna, which I guess their antenna provides?

 

Well, here is the pertinent excerpt from their manual:

image.png.036611952a29b45e9b6dcb27fd74e1a6.png

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That suggests the Power Amplifier output is protected from reflections for the case where no load is connected.   That makes it even stranger if it is fragile to having a portable antenna connected.

It's also weird that the manual for mine doesn't have the warning.

Also, while it isn't a bad idea, the G-test isn't strictly required.   My previous IAs never did it, and I don't do it.   There is obviously risk in doing it, not the least of which is that if you don't do it right and it transmits a 406 signal you might have the Air Force hunting you down to investigate.    This shouldn't happen if you use the test button on the RCPI to do the self test, since it transmits a test signal in that case that is distinct from the signal transmitted after a G-induced activation.

image.png.55664d11445299745d8d451e30ded934.png

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Ooh, I think I might see what may be going on.     When activated with the G-switch it transmits on 121.5 MHz for nearly a minute before transmitting on 406 MHz.   The initial transmission of an ELT on 406MHz is not a single burst, but several repetitions of the first burst, so it lasts for a while.   The 121.5 MHz signal is only 125 mW (milliWatts), the 406 signal is 5 Watts (40 times as much).   So the warning in red letters about not letting it transmit for more than thirty seconds is to keep it from blasting 5 W back into the Power Amplifier with no load (as well as keeping the Air Force from getting too excited about it).  It may be able to handle the 125 mW reflection, but the 5 W may be too much for it.

That should be less of an issue with an antenna connected than without one, so I'm still puzzled why it'd be a bad idea to connect an antenna, but who knows.  Maybe that's just to reduce the likelihood of getting the Air Force involved.   Or there may be something about their particular output circuit that responds that way.

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2 hours ago, Fly Boomer said:

and it will radiate enough with no antenna to pick up on a nearby handheld

Being heard on a near by Hand Held doesn't surprise me.  It's the not burning out the Transmitter that does.

However....   I'd love to see the antenna wiring.  I wonder if with no antenna attached they include an internal load.  Then, when you turn it on, odds of a false alarm are greatly reduced as the transmitting power/range is reduced.  But there is still enough output for the Hand Held to pick up.

 

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More internet speculation:  I suspect the output stage amp is wide-band; i.e. one amp handles both transmission on 121.5 MHz and 406 MHz.  As such, at only 125 mW I don't see the output stage being harmed (reflected voltage from an open load won't exceed limits).  However, allow it to transmit at 5 W and the reflected voltage likely exceeds the output stage's rating and...poof, no more transistor!

This speculation is at least consistent with the warnings and procedures in the manual:D

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The E-04 is a complete piece of junk. It carries over the E-01's faulty G-switch problems, and adds it's own random triggers to make life aggravating. 

I have at least four clients who have recurring problems with these ELTs. One is on his second factory repair, and tomorrow I have to remove it yet again and send it back to ACK for yet another repair. It keeps going off in flight. 

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21 minutes ago, PT20J said:

Mine works fine. No false alarms and passes the g switch test at annual.  Haven’t crash tested it, though ;)

Mine too! I just push the test button while listening on a handheld once in a while and skip 3/4 of the stuff on this thread!

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13 hours ago, philiplane said:

The E-04 is a complete piece of junk. It carries over the E-01's faulty G-switch problems, and adds it's own random triggers to make life aggravating. 

I have at least four clients who have recurring problems with these ELTs. One is on his second factory repair, and tomorrow I have to remove it yet again and send it back to ACK for yet another repair. It keeps going off in flight. 

My avionics shop suggested I replace mine during the current avionics upgrade project.

Similar comments to yours.

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