406 ELT Aircraft Installed - Anyone find one? - Internal carbonfuselage antenna

Does anyone have success finding an aircraft installed 406 ELT for a
Schempp-HIrth glider (i.e. internal installed antenna somewhere in
fuselage)?

On Mar 14, 11:51*pm, WaltWX wrote:
Does anyone have success finding an aircraft installed 406 ELT for a
Schempp-HIrth glider (i.e. internal installed antenna somewhere in
fuselage)?

A quarter wave of 406.25 is about 6.9", so a quarter-wave whip antenna
optimized for that frequency would stand about 7" tall. A dipole would
be about 14" tall. It's probably a vertically-polarized signal, so you
want the antenna standing vertically, and not horizontally.

If your glider has a fiberglass fuselage, it is relatively transparent
at the MHz frequencies, so you can use either an internal dipole or an
internal quarter-wave whip with a ground plane. The dipole is probably
the better bet.

If it's an all-carbon fuselage, it is pretty much opaque to the MHz
frequencies, about like an all-aluminum fuselage. No internal antenna
could offer anything like reasonable performance.

If the fuselage is primarily carbon, there may be a few places where
you might make an antenna work. Sometimes the vertical fin or rudder
are fiberglass or aramid; you might be able to put an antenna in one
of those places. I used Jim Weir's design guide to design the internal
123 MHz dipole antenna in the rudder of Brad Hill's Tetra-15
sailplane, and it seems to be working pretty well. The turtledeck area
might also be fiberglass or aramid, so you might be able to install
something there.

Thanks, Bob K.
http://www.hpaircraft.com/hp-24

On Thursday, March 15, 2012 12:32:02 PM UTC-7, Bob Kuykendall wrote:
On Mar 14, 11:51*pm, WaltWX wrote:
Does anyone have success finding an aircraft installed 406 ELT for a
Schempp-HIrth glider (i.e. internal installed antenna somewhere in
fuselage)?

A quarter wave of 406.25 is about 6.9", so a quarter-wave whip antenna
optimized for that frequency would stand about 7" tall. A dipole would
be about 14" tall. It's probably a vertically-polarized signal, so you
want the antenna standing vertically, and not horizontally.

If your glider has a fiberglass fuselage, it is relatively transparent
at the MHz frequencies, so you can use either an internal dipole or an
internal quarter-wave whip with a ground plane. The dipole is probably
the better bet.

If it's an all-carbon fuselage, it is pretty much opaque to the MHz
frequencies, about like an all-aluminum fuselage. No internal antenna
could offer anything like reasonable performance.

If the fuselage is primarily carbon, there may be a few places where
you might make an antenna work. Sometimes the vertical fin or rudder
are fiberglass or aramid; you might be able to put an antenna in one
of those places. I used Jim Weir's design guide to design the internal
123 MHz dipole antenna in the rudder of Brad Hill's Tetra-15
sailplane, and it seems to be working pretty well. The turtledeck area
might also be fiberglass or aramid, so you might be able to install
something there.

Thanks, Bob K.
http://www.hpaircraft.com/hp-24

The tail area is a poor choice for an ELT antenna because the tail boom is quite likely to break in a crash, possible taking the ELT coax cable with it. Typically there is just really no good way to mount an ELT antenna inside a carbon fuselage. The turtle deck and nose deck areas don't have enough space for a vertical antenna and ground plane, even if they are RF opaque glass/kevlar. You might want to consider a 406 MHz PLB attached to the pilot/parachute harness. The PLB won't activate on impact, but then its not clear that ELTs will reliably active on impact either...especially for what may be 'low energy' glider impacts.... all ideally after starting with a SPOT tracker which can deliver many of the benefits of an ELT/PLB and quite a few the ELT/PLB cannot. I still like to also have a 406 MHz PLB since SAR organizations really do understand them and the old fashioned 121.5Mhz local homing beacon built into them can still be useful.

Darryl

On Mar 15, 8:02*pm, Darryl Ramm wrote:
On Thursday, March 15, 2012 12:32:02 PM UTC-7, Bob Kuykendall wrote:
On Mar 14, 11:51*pm, WaltWX wrote:
Does anyone have success finding an aircraft installed 406 ELT for a
Schempp-HIrth glider (i.e. internal installed antenna somewhere in
fuselage)?

A quarter wave of 406.25 is about 6.9", so a quarter-wave whip antenna
optimized for that frequency would stand about 7" tall. A dipole would
be about 14" tall. It's probably a vertically-polarized signal, so you
want the antenna standing vertically, and not horizontally.

If your glider has a fiberglass fuselage, it is relatively transparent
at the MHz frequencies, so you can use either an internal dipole or an
internal quarter-wave whip with a ground plane. The dipole is probably
the better bet.

If it's an all-carbon fuselage, it is pretty much opaque to the MHz
frequencies, about like an all-aluminum fuselage. No internal antenna
could offer anything like reasonable performance.

If the fuselage is primarily carbon, there may be a few places where
you might make an antenna work. Sometimes the vertical fin or rudder
are fiberglass or aramid; you might be able to put an antenna in one
of those places. I used Jim Weir's design guide to design the internal
123 MHz dipole antenna in the rudder of Brad Hill's Tetra-15
sailplane, and it seems to be working pretty well. The turtledeck area
might also be fiberglass or aramid, so you might be able to install
something there.

Thanks, Bob K.
http://www.hpaircraft.com/hp-24

The tail area is a poor choice for an ELT antenna because the tail boom is quite likely to break in a crash, possible taking the ELT coax cable with it. Typically there is just really no good way to mount an ELT antenna inside a carbon fuselage. The turtle deck and nose deck areas don't have enough space for a vertical antenna and ground plane, even if they are RF opaque glass/kevlar. *You might want to consider a 406 MHz PLB attached to the pilot/parachute harness. The PLB won't activate on impact, but then its not clear that ELTs will reliably active on impact either...especially for what may be 'low energy' glider impacts.... all ideally after starting with a SPOT tracker which can deliver many of the benefits of an ELT/PLB and quite a few the ELT/PLB cannot. I still like to also have a 406 MHz PLB since SAR organizations really do understand them and the old fashioned 121.5Mhz local homing beacon built into them can still be useful.

Darryl- Hide quoted text -

- Show quoted text -

I own a PLB also and have it with me for every flight (on my
parachute). I believe that having the government looking for, and
responding to, my emergency beacons (both 406 satellite with GPS
coordinates and old fashioned terrestrial 121.5) is preferable to a
commercial enterprise doing so. Also the recurring cost of a SPOT
quickly overtakes the up front sunk costs of a PLB (zero recurring).
But, of course, the PLB will not provide the tracking information that
SPOT (and the Delorme device) can provide. Not to mention that PLBs
are cheaper than ELTs.

Questions - Why don't the PLB's have self-triggering on impact like
ELTs? False/inadvertant or no triggering? As I understand the marine
version of the PLB will auto-trigger (via moisture). Doesn't the
possibility of a good trigger outweight the false/no trigger? Does
this have to do with the fact the PLBs are handheld and maybe more
prone to being dropped and then falsely triggering?

On Friday, March 16, 2012 8:48:32 AM UTC-7, JohnDeRosa wrote:
On Mar 15, 8:02*pm, Darryl Ramm wrote:
On Thursday, March 15, 2012 12:32:02 PM UTC-7, Bob Kuykendall wrote:
On Mar 14, 11:51*pm, WaltWX wrote:
Does anyone have success finding an aircraft installed 406 ELT for a
Schempp-HIrth glider (i.e. internal installed antenna somewhere in
fuselage)?

A quarter wave of 406.25 is about 6.9", so a quarter-wave whip antenna
optimized for that frequency would stand about 7" tall. A dipole would
be about 14" tall. It's probably a vertically-polarized signal, so you
want the antenna standing vertically, and not horizontally.

If your glider has a fiberglass fuselage, it is relatively transparent
at the MHz frequencies, so you can use either an internal dipole or an
internal quarter-wave whip with a ground plane. The dipole is probably
the better bet.

If it's an all-carbon fuselage, it is pretty much opaque to the MHz
frequencies, about like an all-aluminum fuselage. No internal antenna
could offer anything like reasonable performance.

If the fuselage is primarily carbon, there may be a few places where
you might make an antenna work. Sometimes the vertical fin or rudder
are fiberglass or aramid; you might be able to put an antenna in one
of those places. I used Jim Weir's design guide to design the internal
123 MHz dipole antenna in the rudder of Brad Hill's Tetra-15
sailplane, and it seems to be working pretty well. The turtledeck area
might also be fiberglass or aramid, so you might be able to install
something there.

Thanks, Bob K.
http://www.hpaircraft.com/hp-24

The tail area is a poor choice for an ELT antenna because the tail boom is quite likely to break in a crash, possible taking the ELT coax cable with it. Typically there is just really no good way to mount an ELT antenna inside a carbon fuselage. The turtle deck and nose deck areas don't have enough space for a vertical antenna and ground plane, even if they are RF opaque glass/kevlar. *You might want to consider a 406 MHz PLB attached to the pilot/parachute harness. The PLB won't activate on impact, but then its not clear that ELTs will reliably active on impact either...especially for what may be 'low energy' glider impacts.... all ideally after starting with a SPOT tracker which can deliver many of the benefits of an ELT/PLB and quite a few the ELT/PLB cannot. I still like to also have a 406 MHz PLB since SAR organizations really do understand them and the old fashioned 121.5Mhz local homing beacon built into them can still be useful.

Darryl- Hide quoted text -

- Show quoted text -

I own a PLB also and have it with me for every flight (on my
parachute). I believe that having the government looking for, and
responding to, my emergency beacons (both 406 satellite with GPS
coordinates and old fashioned terrestrial 121.5) is preferable to a
commercial enterprise doing so. Also the recurring cost of a SPOT
quickly overtakes the up front sunk costs of a PLB (zero recurring).
But, of course, the PLB will not provide the tracking information that
SPOT (and the Delorme device) can provide. Not to mention that PLBs
are cheaper than ELTs.

Questions - Why don't the PLB's have self-triggering on impact like
ELTs? False/inadvertant or no triggering? As I understand the marine
version of the PLB will auto-trigger (via moisture). Doesn't the
possibility of a good trigger outweight the false/no trigger? Does
this have to do with the fact the PLBs are handheld and maybe more
prone to being dropped and then falsely triggering?

The reason why PLBs don't impact activate is they are designed to be portable and be handled by consumers. You don't want to drop one or bump it in your backpack and have it go off without the user realizing. Also for best operation many PLBs require an antenna to be manually deplyed, and won't work very well without that, so impact activating them without first putting the antenna up may not make sense.. so you may get unintended alerts when you don't want them and not good performance when you do.

The FCC and others were clearly worried about PLBs getting into consumer hands vs. the more regulated/expensive ELTs. That is apparently related to the reason that a PLB has a morse code "P" (dit dah dah dit) added to the 121..5MHz beacon signal in the USA (but not overseas)... its so those signals could be identified as coming from a PLB and presumably even more ignored by SAR organizations than 121.5MHz ELT beacons -- unless SAR folks knew somebody was missing with a PLB then hopefully seeing a PLB beacon would get SAR folks even more interested. Note its only the 121.5Mhz beacon parts of a 406 MHz ELT or PLB that I'm talking about being 'ignored' False 121.5 alarms from old ELTs happen a lot and SAR organizations just cannot always respond to them, and now the SARSAT/COSPAS satellite network does not monitor 121..5 Mhz at all. If you fire off a modern 406 MHZ ELT and PLB (which all also have a 121.5 MHz beacon final/local SAR organization homing) you *will* get attention from SARSAT and local SAR organizations, alerted initially from the 406 MHz SARSAT/COSPAS satellite network.

Darryl

On Mar 14, 11:51*pm, WaltWX wrote:
Does anyone have success finding an aircraft installed 406 ELT for a
Schempp-HIrth glider (i.e. internal installed antenna somewhere in
fuselage)?

Hi,

I spoke with Schempp-Hirth about that at the Reno Convention and they
recommended a flexible antenna taped around the fuselage, close to the
canopy frame's end rear right hand side. (sorry it's easier to show
then to describe). Now I still need to find the proper antenna type/
model but if you contact SH please let us know as I need to do the
same in my glider.

Uwe