Hi,
grounded27:
How old is HF as used in aircraft and what was the wattage of the first systems?
Amelia Earhart tried HF use (unsuccessfully) in her doomed flight in 1937. They were heard (IIRC, loud and clear) on Itasca (ship) but a probable aerial broked in Lae take off reduced drastically the ERP (effective radiated power) only allowing short distance comm.
I will study to trace the beginning of use of HF on A/C.
The capabilities of first Systems were very limited. They used CW (morse code) thus compensating equipt. limitations. Later on they introduced AM (phone) with limited performance due the use of AM (amplitude modulation. The same used currently used in VHF comm. today).
The power levels were low (due derated RF tubes to increase "TBO" MTBF). For example, the "powerful" Collins ART13 (extensively used in WW II) was rated 100 W only. I have a Bendix TA12 (a good equipt.) with just 40 Watts (AM) from WW II. The "Command Set" designed for gliders. used same power level.
With the introduction of SSB (an highly improved AM) the power levels went to the 400 w PEP (peak envelope power) standard today. Enough to you be heard by
good operators in ground stations. (not always the case
)
Based in my experience of ~ 5,000 hours of (land mobile) continuous HF use (SSB or CW/morse 500 W power level) i can say with a proper selection of frequency and with a good (efficient) antenna you have (most* of time)
WORLD WIDE comm.
The problems faced in A/C using HF are to be commented later. Derives from several factors.
Mac
(*) With CW (Morse) ALL TIME: 99,99%,
