ELT antenna question.

[Moobie]

Got back from a flight and noticed my ELT antenna got broke off by something(bird?) I'm not sure how to get it off as it seems that the cable is twisting with the nut. Also wasnt sure if I should turn off the ELT when replacing it?

 

Andy

 

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[Marauder]

9 minutes ago, Moobie said:

 

Got back from a flight and noticed my ELT antenna got broke off by something(bird?) I'm not sure how to get it off as it seems that the cable is twisting with the nut. Also wasnt sure if I should turn off the ELT when replacing it?

 

Andy

 

Sent from my SM-G935V using Tapatalk

 

 

 

The ELT shouldn't go off with the antenna removal. Based on the rust I am seeing, I think I would using some penetrate on it might help (I like SeaFoam's Deep Creep). I would think there is a backing nut on the avionics side of the connection that could be used to prevent it from spinning.

[RLCarter]

Which nut are you trying to loosen, inside or outside ?

[Moobie]

Which nut are you trying to loosen, inside or outside ?

I was trying the outside. I now see the nut on the inside. Definitely going to be a 2 person job. I'm going to have to pull a few contortions to reach the inside nut while somebody turns the outside.

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[RLCarter]

37 minutes ago, Moobie said:

I was trying the outside. I now see the nut on the inside. Definitely going to be a 2 person job. I'm going to have to pull a few contortions to reach the inside nut while somebody turns the outside.

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The outside nut is held stationary and you loosen the inside nut, the coax is made into the outside nut

[EricJ]

You should turn the ELT off when fiddling with the antenna, and I'd even disconnect the antenna cable at the ELT before working on the antenna.   This will help protect the output of the power amplifier from any transients or static discharge while you're handling the conductors around the antenna.

If the ELT transmitter comes on (inadvertently or for whatever reason) while the antenna is missing or disconnected it can damage the transmit power amplifier.   Likewise handing the output conductor via static discharge (from a person or a tool to it). 

Once you're all done with an antenna replacement, execute the self test and make sure it can be heard strongly on a 121.5 receiver.   That'll let you know that the amplifier survived the entire process.

 

[Guest]

5 hours ago, RLCarter said:

The outside nut is held stationary and you loosen the inside nut, the coax is made into the outside nut

I’m sure that’s backwards, you need to hold the inner nut and then loosen and remove the outer nut.  The coax is secured to the inner nut and stud.

Time to upgrade to a 406 MHz ELT looks like it’s come.

Clarence

Edited March 19, 2019 by M20Doc

[Yetti]

14 hours ago, EricJ said:

If the ELT transmitter comes on (inadvertently or for whatever reason) while the antenna is missing or disconnected it can damage the transmit power amplifier.   Likewise handing the output conductor via static discharge (from a person or a tool to it). 

 

 

While normally I would agree with your statement the new 406 ACK says to remove the antenna while doing the swing test.   I think they don't want a 406 alert going out on accident.  And the transmitter is low enough power to not take out the power amp.

I would think the outer coax braid is under the outer nut and there is probably another nut under that one.

[EricJ]

4 hours ago, Yetti said:

While normally I would agree with your statement the new 406 ACK says to remove the antenna while doing the swing test.   I think they don't want a 406 alert going out on accident.  And the transmitter is low enough power to not take out the power amp.

I would think the outer coax braid is under the outer nut and there is probably another nut under that one.

Some of the newer stuff is less sensitive to the impedance mismatch created by a missing load (antenna), so I'm not too surprised.  Not sure what a swing test is, though.

That said, the 406 units (I have an ACK-04, too) still have self-test modes,  .   My ACK-04 manual says that it is supposed to be self-tested every three months, and there's no mention of removing the antenna.   I think the self-test 406 signal is distinguishable from the activated signal, so I don't think that's a problem.   You can still listen on 121.5 for the one-second test signal.

I did get a call from the Air Force when the avionics guys set mine off in their shop and didn't know it.   Was nice to know the system works.