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Low-profile or Short 121.5 ELT Antenna options?

Darinh

Well Known Member
My ELT antenna is located on the bottom of my fuse and due to clearance issues with grass strips (builder lived on a grass strip) it has broken at the base and I’m sure is worthless as it just flips around. It appears to be a Pointer 3000-1 12” antenna.

Does anyone know if a shorter option or low-profile option that can be used? Pointer makes a 7” version but I can’t find one and a call to Pointer didn’t yield any helpful options. Short of ordering one from Skygeek and waiting an indeterminate amount of time for it to be manufactured and shipped, I’m hoping there are other viable options. I don’t know much about antenna theory (nothing, actually) but I assume you just can’t use any old antenna for this? There doesn’t seem to be any options other than the typical 12” - 18” whips out there.
 
Here is the pointer 121.5 short antenna.
 

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You understand, I presume, that mounting the elt antenna on the bottom of the airplane is contrary to the TSO’d installation instructions….
 
I see how someone with a fully functioning analog 121.5 system here might want to continue with it until they have to upgrade, but personally, I wouldn't put a dime into keeping the old system chugging along.
Analog systems haven't been monitored by SARSAT since 2009, and digital 406 systems are vastly superior in every way. 406 tech is already required in Mexico, Canada and a lot of the Caribbean. It's just a matter of time when it will be required here as well.

https://www.avweb.com/ownership/the-411-on-406s/
 
You understand, I presume, that mounting the elt antenna on the bottom of the airplane is contrary to the TSO’d installation instructions….

I wasn’t aware of this but I also am not the builder. I suspect his reason for mounting it on the bottom is because of it needed, you’ve likely had a forced landing and the airplane has flipped over which I also suspect is common when forced to land on anything other than pavement or a purpose built grass runway. An antenna on the top would simply be crushed and broken and rendered useless in this case. So, I think the installation on the bottom is actually a smart move on the original builders part TSO’d or not.
 
I see how someone with a fully functioning analog 121.5 system here might want to continue with it until they have to upgrade, but personally, I wouldn't put a dime into keeping the old system chugging along.
Analog systems haven't been monitored by SARSAT since 2009, and digital 406 systems are vastly superior in every way. 406 tech is already required in Mexico, Canada and a lot of the Caribbean. It's just a matter of time when it will be required here as well.

https://www.avweb.com/ownership/the-411-on-406s/

Good point…I put a 406 in my Kit Fox back in 2008. Maybe it’s time to change this system out. I haven’t looked into 406 ELTs for some time. Maybe there are some that are a bit less expensive than they used to be.
 
An antenna on the top would simply be crushed and broken and rendered useless in this case. So, I think the installation on the bottom is actually a smart move on the original builders part TSO’d or not.

Smart move or not, if it does not conform to the installation instructions, it is not legal. Typically if the aircraft is upside down, the ELT antenna is protected by the vertical stabilizer.
 
Smart move or not, if it does not conform to the installation instructions, it is not legal. Typically if the aircraft is upside down, the ELT antenna is protected by the vertical stabilizer.

Mel, being that its illegal, how would it have passed its inspection and received an airworthiness cert back in 2005? Not trying to be contentious here, I am really interested? I assume that is something that is scrutinized during a DAR's inspection? It seems I have seen helicopters with ELT antennas mounted on the bottom side of the boom. Is it illegal to mount an ELT antenna on the bottom of any aircraft or just fixed wing?

The installation of a 406 MHz is a good idea and I will probably move in that direction, particularly since I can't seem to find a suitable antenna. This will allow me to relocate the antenna.
 
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Mel, being that its illegal, how would it have passed its inspection and received an airworthiness cert back in 2005? Not trying to be contentious here, I am really interested? I assume that is something that is scrutinized during a DAR's inspection? It seems I have seen helicopters with ELT antennas mounted on the bottom side of the boom. Is it illegal to mount an ELT antenna on the bottom of any aircraft or just fixed wing?
The installation of a 406 MHz is a good idea and I will probably move in that direction, particularly since I can't seem to find a suitable antenna. This will allow me to relocate the antenna.

The DAR is responsible to see that the aircraft meets §21.191.
We are not policemen. The owner/operator is responsible for operational issues. The installation on helicopters will be contained in the ELT installation manual.
 
I am an antenna expert :rolleyes::D Well it's a hobby. Let me get to my answer first. You should not replace the antenna. You should buy a new ELT with the matching antenna. I will tell you why I suggest that. As you may know this is an older ELT's that transmits on 121.5 MHz and 243 Mhz. BOTH of these are no longer monitored, so to speak. The new frequency is 406 Mhz is monitored by satellites whose job is to find you and aviator and sailors, and very very accurate. It transmits your unique identity and can also optionally send GPS position. However without GPS the accuracy is very good. The old system no longer monitored was not accurate or timely. Better than nothing, but new technology is light years better.

Seriously I am not a pointer Pointer 3000-1 expert (or is it Pointer 3000-10), but pretty sure either way this is an older ELT. If you REALLY want the advantage of safety and accurate position location get a new ELT. Also ELT's are TSO'ed "systems" and the antenna is part of that. You can't mix and match any other antenna. Again old ELT might as well replace the whole ELT and antenna.
  • ACK 406/121.5 MHz E-04 ELT FAA TSO
  • ARTEX 345 406

Pointer ELT for 406 is their 8000 series. It is a new design so it does not use the 3000 series mount hardware or antenna. Pointer is more expensive than above models, so no advantage going Pointer.

Most ELT antenna even the new 4O6 Mhz models have antennas about 20-23" long. ARTEX has a 15" ELT antenna option. The driving factor is the 121.5 Mhz which is still part of the new ELT's. The 121.5 is for that last mile to "home" to airplane with Direction Finders. The ideal antenna length for 121.5" is about 18". If it was just for 406 Mhz the antenna could be 6" for a 1/4 or quarter length antenna. So 18" would be approx 3/4 wave for 406 Mhz. Some ELT antennas are shorter by using a base loaded coil in the antenna to trick the RF signal into seeing the antenna as electrically longer. That is why your antenna may be shorter?

You say your current antenna is 12" ? You are not going to get much shorter (but I am not 100% sure). Most ELT antennas I see are in the 20" ball park, they can be shorter, however the antenna has to match ELT's which are TSO'ed systems, and you MUST use the exact antenna part number that it was designed to use or an approved substitute by the manufacture.

WHY YOU NEED A NEW ELT - The new 406 ELT's are VERY accurate and transmit your unique identification (that is registered to you and your plane). The 406 beacon will be detected faster, more often and with precision. The 243 is not officially monitored any more and the satellites are not over head often and can not locate the signal with any precision. Also you can transmit your GPS position as an option. I was told by ELT manufacture that even without GPS data it is very accurate, way better than the older ELT's even on their best day. You might be lucky and get someone monitoring 121.5 Mhz but the range can be as short as a few 1000 feet to 5 miles in ideal line of sight condition. It is only 200 milli-watts transmitter. We transmit typically with our COM radio 5 to 10 watts. Your old ELT has 25 to 50 times less power. If you keep with the Pointer you really are checking a box to fill a regulation but it is pretty useless. These ELT's were to be phased out and no longer legal to use. The GOV backed down from the mandate, at least for now. I recall all new ELT installations going forward require the 406 ELT. You are repairing your old one so that is OK I believe?

The old ELT's date back to original FAA specs from early 1970's. This is old technology. One big reason to switch are false alarms. It is a huge pain, loss of big money (which you might be liable for) and resources to chase down false ELT alarms. With the new 406 has precision location (faster to find) and an ID with contact info. They can call you or at least find the location quickly wasting less time and money. Also new ELT's have newer battery technology that lasts up to 5 yrs for the one I know of.

DRAG and CLUTTER, HIDE THE ANTENNA - If you are worried about "drag" and antenna clutter on your sleek RV sky scooter, you can mount in the baggage area next to the plexi glass. Not as good as outside but not totally bad. Say you put it on the outside, top back and flip over? The antenna would be in the dirt. If you have it on the belly it is not ideal either unless you flip. :D
 
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Great information, GMCjetpilot!

I am aware of the benefits of the 406 systems and installed one In my Kitfox back in 2008 when I built it. I’ll move in that direction. Thanks all!
 
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