What's this term mean?

Tom-D

Tom-D

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Tom-D
On page #45 in the wire skit pin #9 is labeled ELT-RX

what does "RX"
what is that pin used for?

http://www.sportys.com/media/pdf/artex345.pdf

I'll call Monday to verify, but it is late Friday night.
Thanks in advance

I think it is the Co-Ax connection for the transmitter ? But they put it in the D sub connector.. confusing .
 
Last edited:
Tom-D said:
On page #45 in the wire skit pin #9 is labeled ELT-RX

what does "RX"
what is that pin used for?
http://www.sportys.com/media/pdf/artex345.pdfhat a "skit'

I'll call Monday to verify, but it is late Friday night.
Thanks in advance

I think it is the Co-Ax connection for the transmitter ? But they put it in the D sub connector.. confusing .
Click to expand...
RX is the radio abbrvtn for "receive data" or "receiver input". I have no idea what a "skit" is.

Jim
 
Tom-D said:
On page #45 in the wire skit pin #9 is labeled ELT-RX

what does "RX"
what is that pin used for?

http://www.sportys.com/media/pdf/artex345.pdf

I'll call Monday to verify, but it is late Friday night.
Thanks in advance

I think it is the Co-Ax connection for the transmitter ? But they put it in the D sub connector.. confusing .
Click to expand...

That’s Pin 9 of the D-SUB connector. It’s serial NMEA data from an approved GPS for continuous location information to be fed to the ELT. It is NOT RF. Absolutely not.

When a 406 ELT is activated, it sends its last known position immediately if a GPS is feeding it data (example: activated by the remote switch in flight prior to an off airport landing) it will continue to update that position data in transmissions sent in the data burst until it no longer receives data from the on-board GPS.

This is how 406 ELTs are light years ahead of their dumb 121.5 “beacon” counterparts. They’re not just “homing” devices. They send their location, as fed from the on board panel GPS as soon as they’re activated. SAR literally travels straight to the position.

They don’t wail like a traditional 121.5 ELT all the time. Their main job is to send a data burst to the satellite on orbit which is relayed to AFRCC. If they have a wail/beacon on 121.5 they do it intermittently in-between data packets at a much much reduced power level. You have to be a lot closer to them to “home in” on them than a traditional 121.5 wailer.

They CAN be installed without a GPS source. But if installed that way they’re not much better than a 121.5 beacon. They’ll transmit the aircraft’s tail number essentially, by transmitting their discreet ELT ID number, which must be registered to the aircraft tail number by the installer or owner. Instructions on how to register are included with the ELT. And their power output as a beacon is reduced and they’re also difficult to home in on the full power data packets without special homing gear due to the less frequent nature of the transmissions.

CAP aircraft with Becker SAR radios as well as USCG with the exact same radio, it can “average” the location and direction in homing mode because it knows the transmission is infrequent, but older left/right antenna and gear can’t easily home directly to a 406 beacon. You have to know how the beacon works to do your own manual averaging and ignore the needle indications when there’s no data packet “blast” present on the frequency. Same with older Doppler DF gear. You’ll just be homing on noise if you pay any attention to the direction indicated when the ELT packet data noise is not being heard by your receiver.

Note: The serial interface on that is one wire. Serial data requires a transmit and a ground. They appear to be using the common airframe ground for both the ground for the data and the ground for the remote activation switch closure. Not my favorite way to do serial data.

I’d make damn sure that the ELT is “copying” the NMEA serial stream from the panel GPS by scheduling a test where the transmitted data burst can be read properly with a proper 406 ELT receiver or worst case, a call to AFRCC. Or however else the manufacturer suggests to test the NMEA input to the ELT. I wouldn’t trust a one wire serial connection with airframe ground to be working without some way to see that the ELT is seeing each 4800 b/sec packet from the GPS and properly decoding it.

There’s probably data on how to test the NMEA serial line somewhere in that doc. I didn’t read all of it. If not, ask Artex how you ensure the serial data from the GPS is being decoded properly by the ELT before letting that thing out of the shop.

A quick Google shows that Artex has a through-the-satellite test function and website for $60 so you can see exactly what the ELT sent during a properly done test that will not trigger SAR or require contact with AFRCC.

http://www.406test.com/overview.aspx

Other information shows...

Once that initial test through the satellite is done, it’s up to the shop doing the annual test if they want to do a proper through-the-satellite test or just a quick listen for the weak 121.5 wail.

It’s recommended to keep tests less than 30 seconds to not have them received and decoded by the satellites.

Technically I’m sure the satellites hear it anyway, they’re just saying AFRCC will ignore transmissions less than 30 seconds.
 
denverpilot said:
That’s Pin 9 of the D-SUB connector. It’s serial NMEA data from an approved GPS for continuous location information to be fed to the ELT. It is NOT RF. Absolutely not.

When a 406 ELT is activated, it sends its last known position immediately if a GPS is feeding it data (example: activated by the remote switch in flight prior to an off airport landing) it will continue to update that position data in transmissions sent in the data burst until it no longer receives data from the on-board GPS.

This is how 406 ELTs are light years ahead of their dumb 121.5 “beacon” counterparts. They’re not just “homing” devices. They send their location, as fed from the on board panel GPS as soon as they’re activated. SAR literally travels straight to the position.

They don’t wail like a traditional 121.5 ELT all the time. Their main job is to send a data burst to the satellite on orbit which is relayed to AFRCC. If they have a wail/beacon on 121.5 they do it intermittently in-between data packets at a much much reduced power level. You have to be a lot closer to them to “home in” on them than a traditional 121.5 wailer.

They CAN be installed without a GPS source. But if installed that way they’re not much better than a 121.5 beacon. They’ll transmit the aircraft’s tail number essentially, by transmitting their discreet ELT ID number, which must be registered to the aircraft tail number by the installer or owner. Instructions on how to register are included with the ELT. And their power output as a beacon is reduced and they’re also difficult to home in on the full power data packets without special homing gear due to the less frequent nature of the transmissions.

CAP aircraft with Becker SAR radios as well as USCG with the exact same radio, it can “average” the location and direction in homing mode because it knows the transmission is infrequent, but older left/right antenna and gear can’t easily home directly to a 406 beacon. You have to know how the beacon works to do your own manual averaging and ignore the needle indications when there’s no data packet “blast” present on the frequency. Same with older Doppler DF gear. You’ll just be homing on noise if you pay any attention to the direction indicated when the ELT packet data noise is not being heard by your receiver.

Note: The serial interface on that is one wire. Serial data requires a transmit and a ground. They appear to be using the common airframe ground for both the ground for the data and the ground for the remote activation switch closure. Not my favorite way to do serial data.

I’d make damn sure that the ELT is “copying” the NMEA serial stream from the panel GPS by scheduling a test where the transmitted data burst can be read properly with a proper 406 ELT receiver or worst case, a call to AFRCC. Or however else the manufacturer suggests to test the NMEA input to the ELT. I wouldn’t trust a one wire serial connection with airframe ground to be working without some way to see that the ELT is seeing each 4800 b/sec packet from the GPS and properly decoding it.

There’s probably data on how to test the NMEA serial line somewhere in that doc. I didn’t read all of it. If not, ask Artex how you ensure the serial data from the GPS is being decoded properly by the ELT before letting that thing out of the shop.

A quick Google shows that Artex has a through-the-satellite test function and website for $60 so you can see exactly what the ELT sent during a properly done test that will not trigger SAR or require contact with AFRCC.

http://www.406test.com/overview.aspx

Other information shows...

Once that initial test through the satellite is done, it’s up to the shop doing the annual test if they want to do a proper through-the-satellite test or just a quick listen for the weak 121.5 wail.

It’s recommended to keep tests less than 30 seconds to not have them received and decoded by the satellites.

Technically I’m sure the satellites hear it anyway, they’re just saying AFRCC will ignore transmissions less than 30 seconds.
Click to expand...
IOWs we have no GPS on board, we don't use this pin?
 
Yes, you can skip that pin. But I would still run a line from the ELT to the panel from that pin to make hooking it up easier later. I believe some modern portable GPS units have an NMEA output as well.
 
And, FWIW, if one were to connect the RX pin to a GPS source, it would connect to a TX pin on the GPS, not an RX.
 
Capt. Geoffrey Thorpe said:
And, FWIW, if one were to connect the RX pin to a GPS source, it would connect to a TX pin on the GPS, not an RX.
Click to expand...

That too. Also, don’t some modern transponders with built in GPS for ADS-B have suitable NMEA outputs?
 
denverpilot said:
That’s Pin 9 of the D-SUB connector. It’s serial NMEA data from an approved GPS for continuous location information to be fed to the ELT. It is NOT RF. Absolutely not.

When a 406 ELT is activated, it sends its last known position immediately if a GPS is feeding it data (example: activated by the remote switch in flight prior to an off airport landing) it will continue to update that position data in transmissions sent in the data burst until it no longer receives data from the on-board GPS.

This is how 406 ELTs are light years ahead of their dumb 121.5 “beacon” counterparts. They’re not just “homing” devices. They send their location, as fed from the on board panel GPS as soon as they’re activated. SAR literally travels straight to the position.

They don’t wail like a traditional 121.5 ELT all the time. Their main job is to send a data burst to the satellite on orbit which is relayed to AFRCC. If they have a wail/beacon on 121.5 they do it intermittently in-between data packets at a much much reduced power level. You have to be a lot closer to them to “home in” on them than a traditional 121.5 wailer.

They CAN be installed without a GPS source. But if installed that way they’re not much better than a 121.5 beacon. They’ll transmit the aircraft’s tail number essentially, by transmitting their discreet ELT ID number, which must be registered to the aircraft tail number by the installer or owner. Instructions on how to register are included with the ELT. And their power output as a beacon is reduced and they’re also difficult to home in on the full power data packets without special homing gear due to the less frequent nature of the transmissions.

CAP aircraft with Becker SAR radios as well as USCG with the exact same radio, it can “average” the location and direction in homing mode because it knows the transmission is infrequent, but older left/right antenna and gear can’t easily home directly to a 406 beacon. You have to know how the beacon works to do your own manual averaging and ignore the needle indications when there’s no data packet “blast” present on the frequency. Same with older Doppler DF gear. You’ll just be homing on noise if you pay any attention to the direction indicated when the ELT packet data noise is not being heard by your receiver.

Note: The serial interface on that is one wire. Serial data requires a transmit and a ground. They appear to be using the common airframe ground for both the ground for the data and the ground for the remote activation switch closure. Not my favorite way to do serial data.

I’d make damn sure that the ELT is “copying” the NMEA serial stream from the panel GPS by scheduling a test where the transmitted data burst can be read properly with a proper 406 ELT receiver or worst case, a call to AFRCC. Or however else the manufacturer suggests to test the NMEA input to the ELT. I wouldn’t trust a one wire serial connection with airframe ground to be working without some way to see that the ELT is seeing each 4800 b/sec packet from the GPS and properly decoding it.

There’s probably data on how to test the NMEA serial line somewhere in that doc. I didn’t read all of it. If not, ask Artex how you ensure the serial data from the GPS is being decoded properly by the ELT before letting that thing out of the shop.

A quick Google shows that Artex has a through-the-satellite test function and website for $60 so you can see exactly what the ELT sent during a properly done test that will not trigger SAR or require contact with AFRCC.

http://www.406test.com/overview.aspx

Other information shows...

Once that initial test through the satellite is done, it’s up to the shop doing the annual test if they want to do a proper through-the-satellite test or just a quick listen for the weak 121.5 wail.

It’s recommended to keep tests less than 30 seconds to not have them received and decoded by the satellites.

Technically I’m sure the satellites hear it anyway, they’re just saying AFRCC will ignore transmissions less than 30 seconds.
Click to expand...
Great explanation. Thanks!
 
I'm missing some thing..

Why would you hook up a portable GPS (PLB) to a fixed ELT transmitter? This ELT has an internal GPS that gives the latest Position to the output. But what this unit lacks is a portable antenna.

Unless of course you can remove the ELT from the wreckage and carry it with you. If that is the case, why would you add a wire to the aircraft wire harness?
 
flyer770 said:
Yes, you can skip that pin. But I would still run a line from the ELT to the panel from that pin to make hooking it up easier later. I believe some modern portable GPS units have an NMEA output as well.
Click to expand...
Thanks
 
Capt. Geoffrey Thorpe said:
And, FWIW, if one were to connect the RX pin to a GPS source, it would connect to a TX pin on the GPS, not an RX.
Click to expand...

Is there any way to test a completed installation? To ensure the G switch works, the manual switch works, that it is broadcasting on the right frequency, the right wattage, giving the location correctly? Maybe avionics shops can do all this?
Would seem pointless to install a 'quiet' device and not ever know if its going to work properly when needed.
 
Tom-D said:
I'm missing some thing..

Why would you hook up a portable GPS (PLB) to a fixed ELT transmitter? This ELT has an internal GPS that gives the latest Position to the output. But what this unit lacks is a portable antenna.
Click to expand...

No. That ELT does NOT have an internal GPS. It can only transmit it's precise position if it is connected to an external GPS position source. In the manual you linked, read page 17, bullet points #2 and #5.
 
Let'sgoflying! said:
Is there any way to test a completed installation? To ensure the G switch works, the manual switch works, that it is broadcasting on the right frequency, the right wattage, giving the location correctly? Maybe avionics shops can do all this?
Would seem pointless to install a 'quiet' device and not ever know if its going to work properly when needed.
Click to expand...
On at least some units, there is a test output that will tell you if it is getting the NMEA data in the proper format (including baud rate). For frequency / warts / etc you would need some fancy dancy equipment.
 
slacktide said:
No. That ELT does NOT have an internal GPS. It can only transmit it's precise position if it is connected to an external GPS position source. In the manual you linked, read page 17, bullet points #2 and #5.
Click to expand...

That is correct. The idea that every 406 has an internal GPS is a common misconception amongst the masses. Pilots, plane owners, mechanics, etc. should really read the published material on a unit before buying. It’s called research.
 
Capt. Geoffrey Thorpe said:
On at least some units, there is a test output that will tell you if it is getting the NMEA data in the proper format (including baud rate). For frequency / warts / etc you would need some fancy dancy equipment.
Click to expand...

I must review the fars on this.
Seems like it was an annual requirement to test the elt function, maybe that is only for 121.5 elts.
If a requirement for all elts, I wonder how the 406 elts are getting tested.
 
slacktide said:
No. That ELT does NOT have an internal GPS. It can only transmit it's precise position if it is connected to an external GPS position source. In the manual you linked, read page 17, bullet points #2 and #5.
Click to expand...
  1. 2) The information contained in the message includes:
    1. a) Beacon serial number, or

    2. b) Aircraft identification or registration number

    3. c) Country of registration and country code

    4. d) Position coordinates, if beacon is programmed to receive position data from the aircraft navigation system

      1. 5) The location accuracy of the 406 MHz transmitter is typically 3 km. If position information is extracted from the aircraft navigation system, the accuracy improves to approximately 100 meters (standard or national location protocol).

        My take on this is, it improves with a GPS input, but will give the last position prior to the activation.
 
Tom-D said:
My take on this is, it improves with a GPS input, but will give the last position prior to the activation.
Click to expand...
Nope.
No GPS, no position provided by the ELT.
The 3km number comes from the satellites estimating where the signal is coming from.
 
Well.. SCAT..
3) When the 406 MHz signal is detected by the Cospas–Sarsat satellite system, a position is calculated and the 121.5 MHz signal is used to home in on the crash site.
 
Tom-D said:
My take on this is, it improves with a GPS input, but will give the last position prior to the activation.
Click to expand...

Your take is incorrect. Without a GPS input, the Artex 345 has absolutely no idea at all what it's position is, and it does not transmit it's position when activated. When activated, it only transmits the beacon serial number, the registration number, and the country of registration. Multiple satellite passes are required to determine the position by triangulation, which may take several hours, and the best accuracy that they can get is within 3 km. If it is connected to an external GPS position source, it also includes the latitude/longitude in the transmission, and the position is known within minutes, to an accuracy of 100 meters.
 
slacktide said:
Your take is incorrect. Without a GPS input, the Artex 345 has absolutely no idea at all what it's position is, and it does not transmit it's position when activated. When activated, it only transmits the beacon serial number, the registration number, and the country of registration. Multiple satellite passes are required to determine the position by triangulation, which may take several hours, and the best accuracy that they can get is within 3 km. If it is connected to an external GPS position source, it also includes the latitude/longitude in the transmission, and the position is known within minutes, to an accuracy of 100 meters.
Click to expand...
Yep,, figured that out,, Don't know what I'd do with out you guys ,, :)

Pin 9 wire is installed, we will see what the owner wants to do with the radio stack later, for now the ELT will comply with 91.207, So we be legal to fly.
Main objective now is get it flying, then who knows.
 
Oh....:D

symbol-Rx-6.jpg

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Last edited:
Tom-D said:
Well.. SCAT..
3) When the 406 MHz signal is detected by the Cospas–Sarsat satellite system, a position is calculated and the 121.5 MHz signal is used to home in on the crash site.
Click to expand...

Misleading. Kinda. The 406 signal is data, the 121.5 is a sweep beacon just like the old system.

If the data packet sent up says “I’m at X/Y coordinates” searchers are going to start searching there and not give a crap about DFing the sweep. DFing has multiple difficulties and requires more skill to do than reading the coordinates received by AFRCC and going there.

If you want the benefits of the new tech, you feed GPS data into the ELT for the most part. The 121.5 sweep is simply “backward compatibility” with old tech and techniques AND at a lower RF power output so harder to DF than the original 121.5 ELTs.

The “3km” vs “100m” thing is this:

3km: Multiple satellite passes (takes time) judging where a signal is by AOS/LOS (acquisition of signal, loss of signal) as they pass overhead.

100m: Standard GPS accuracy in a last known position fed to the ELT transmitter prior to activation, which simply sends it to the satellite. (If your feed to the ELT is GPS+WAAS derived it’s even better accuracy.)

The Artex (depending on model) only knows where it is by the serial GPS data fed to it from an external GPS if it’s a typical model.

SOME have their own GPS in them but still may need on board location data to pre-fed the GPS so it doesn’t have to do a GPS “cold start” to figure out where it is on the planet. That takes many minutes.

In contrast, many boating EPIRBs have some way to determine their own location, for example. Exact same technology, same frequencies, everything. Just water activated instead of G force activated. But many of those are also wired into the ship’s main GPS receiver as well, to avoid the cold start problem.

But anyway. Simple Artex models are relying on an external source of location prior to activation. Whatever is in the location buffer when they activate, is what they send.
 
Checkout_my_Six said:
then there is the ADS-B out bread crumb trail.....
Click to expand...

If you’re in ADS-B coverage and using UAT or radar site coverage and using Mode-S. At an altitude where any of it is useable.

SARSAT sees a lot more territory than ADS-B does.
 
denverpilot said:
If you’re in ADS-B coverage and using UAT or radar site coverage and using Mode-S. At an altitude where any of it is useable.

SARSAT sees a lot more territory than ADS-B does.
Click to expand...
not on the east coast.....:D
 
GeorgeC said:
Some 406 ELTs have internal GPS.
Click to expand...
Here is what Spruce says:

When an emergency happens, rely on the same brand that leading aircraft manufacturers trust for first-class quality, superior technology, and outstanding customer service.

The ARTEX ELT 345 is built to the industry’s most stringent quality management standards to ensure the ELT works the first time, every time. The ARTEX ELT 345 transmits on 406 MHz and 121.5 MHz frequencies while providing position accuracy thanks to the built-in GPS navigational interface. GPS data is embedded within the first emergency transmission and provides Search and Rescue personnel with the aircraft location, within 100 meters, in less than a minute.

The ELT 345 boasts an industry low price for an ELT, providing the same quality and performance on which the ARTEX brand was built.

FAA approved.

And why I advised owner to buy. Very misleading and possibly a false statement.
 
Tom-D said:
Very misleading and possibly a false statement.
Click to expand...

I'd agree with that. They should make it clear in the ad copy that it only transmits the GPS position when it is connected to an external GPS position source. It seems like it is written to be intentionally misleading.
 
Tom-D said:
And why I advised owner to buy. Very misleading and possibly a false statement.
Click to expand...

He could have downloaded the manual first and checked. 406 ELTs aren’t exactly new tech at this point.

It does have a “GPS navigational INTERFACE”.

It does not have a “GPS receiver”.

You found the “interface” right there at Pin 9 of the D-Sub connector. :)
 
slacktide said:
I'd agree with that. They should make it clear in the ad copy that it only transmits the GPS position when it is connected to an external GPS position source. It seems like it is written to be intentionally misleading.
Click to expand...

But the next question is, what should we use to feed pin 9 that data to get a position to transmit.
 
denverpilot said:
He could have downloaded the manual first and checked. 406 ELTs aren’t exactly new tech at this point.

It does have a “GPS navigational INTERFACE”.

It does not have a “GPS receiver”.

You found the “interface” right there at Pin 9 of the D-Sub connector. :)
Click to expand...
How would a non-geek know that ? but to learn it the hard way.
 
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