I mentioned the current VERY POOR ANTENNAS because they are also parallel to the vertical fin what further degrades the performance.
Edited:
The shunting feed of VS is a good solution.
Itīs not "an antenna parallel to VS" as i thought.
Itīs a way to feed RF to the VS metal structure.
It has some disadvantages but works.
The efficiency could be good with a low SWR and a good ATU.
About effectiveness i reiterate the wire antennas used in old birds presented much higher ERP.
But the jet age (a/c speed) and space age (SAT) reduced the relative importance of HF to a/c comm.
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Initial post
With the advances in other options HF had a decrease in it`s use.
The old wire antennas were much more effective. But with the jet age they were no longer used.
The "integrated" antennas are low efficiency radiators compared to the ones used in L188, C130`s and the older planes.
Electrically speaking the basis is the low radiation resistance and it`s lenght and position in the a/c.
If the commercial planes were equipped with good HF antennas the comm would be completely different.
After a trip with DEP 2 hours from now i will post a better reply with the laptop.
Well, letīs continue:
A short antenna has several disadvantages compared to one that is in the order of the magnitude of the wave lenght you are using.
At night in June in the middle of the night you may be required to use a low HF frequency.
When i worked doing HF equipt. maintenance in the rigs from PAA (12ACX, 4WTFA, etc) i remember the QRG 2910 KHz. An adequate lenght would be in the range of 60 ft. The Connies, etc used good antennas (long). With an old Collins ART-13 with derated tube to 100 W you had a very strong signal in AM.
Later with the introduction of SSB (USB, for aviation) it was possible to reduce the size paying some penalties in performance. Anyway the 707 fin and the LH wing antennas used by Lufthansa delivered good signals.
More and more the SIMPLE SYSTEM (using just "free" ionosphere layers) was replaced by repeaters, etc.
For example, this repeaters PLAYED A ROLE in MAC between N600XL and
PR-GTD in Brazil.
I mentioned the current VERY POOR ANTENNAS because they are also parallel to the vertical fin what further degrades the performance.
It works but when you have 40+ years of HF experience in thousands of mobile operation (Land mobile, maritime mobile and air mobile) you has the obligation to say the HF antennas equipping the new planes (letīs say, after 707) ARE POOR.
Finally we must mention some EMI/EMC issues, a challenge for new composite "intensive" a/c.
I could assure that with 200W rms out, SSB and a "normal size antenna" your performance (comm and data) would amaze the younger crew.
Other considerations like S/N (signal to noise ratio), ionospheric propagation, etc i could comment further but this is not the issue here in the AF447 case.
