Yes I was confused
It seems to me (Advanced Class ham KC9PR) that if the antenna was electrically connected directly to the airframe, then the entire airframe would be the antenna, and then there is no ground plane.
CQ CQ CQ KC9PR - No offense, I see your antenna shield was locally grounded, via the tab. Yes I was confused by the type of antenna you had. They are all simple whips, but the antennas with a sealed base and BNC connector are grounded through the mounting base, yours is made through the tab. Sorry KC9PR. Got it.
Bottom line the shielding braid gets ground to the "ground plane".
Also, my ELT came with a whip antenna and a rubber duckie. The whip is mounted on the airframe and the duckie is used once the ELT is out of the plane to make it portable. The ELT also has voice transmission capability.
What brand of ELT came with a rubber duckie? The ACK and Amerking have portable antennas, but "old fashion" car style telescoping chrome metal deals, 1/4, may be 1/2 wave length (22" or 44") antenna?
Anyone is interested in all variations of ground plane/non-ground plane antennas, like a 5/8 gamma match/tuning coil antenna, which does not need a ground plane, here is a good
link. The 5/8 antenna of course is not good for for airplane use at 60" long, but it works well OK even with out a ground plane. Below are some 1/4 wave dipole antennas with clever ways around the no ground plane.
Keep in mind the caveat, ELT's are not required for sailplanes and therefore certified TSO installation is not required. For our RV's I would argue the FAR's do require us to use an ELT, and that ELT must be TSO'ed, meaning installed per the manual with approved antenna. If your ELT came with a rubber duckie than its fine.
Clearly you can make the rubber duckie
work with
some ELT's, just look at all the PLB's, all have short little antennas. However the word
work does not necessarily mean performance, at least on the 121.5 Mhz. That is why PLB's are not substitutes for ELT's, they don't have the performance despite the same rated transmitter power. The antenna is key. On the other hand if your approved TSO'ed antenna with ground plane is smashed under the plane, its not going to work well either. Air-band handheld VHF transceivers use short rubber duckies, but the radio was made to work with that particular antenna. Still they would perform with a full 1/4 wave ground plane antenna.
Artex has the
ME406 ELT that does not allow portable antenna use or odd ball monopole antennas, at least efficiently, but they just came out with the
ME406/P which does have a portable antenna option. They had to make the case out of metal to act as a ground plane. The antenna as you can see is more than a rubber duckie. It cost a little more than the base line ME406. Regardless the base line ME406 CAN NOT be used with a portable antenna of any kind as I'm told. Bottom line they had to change the whole ELT to work well with a portable antenna.