Aerospace/Aviation/vhf radio


why VHF is used in aircraft over HF communication?

Actually HF radio was used in airplanes. My 1947 Culver V had one. One channel 3023.5 KHz. The receiver covered 200 KHz to 1700 KHz. The 200-500 KHz range was for beacons and the rest for broadcast. Both used for homing. The loop was used for getting a fix on the station. When the transmitter was used to communicate the ground station would respond in the low frequency band.
There are several reason VHF became the norm. Smaller antenna and a limited range. HF can travel further distances interfering with other stations across the country in a limited size band. HF is still used but only for travel outside The USA. Flying over to Europe required HF communications because of the range needed to be in communications. As electronics improved so did aircraft systems. Got my IFR ticket using HF flying the adcock ranges to navigate. Then came VOR that is still used. However several others a came into use. RNAV, Loran (HF) and now GPS (UHF). I have often wondered why AM for airplanes? Narrow band FM would be more efficient. But the technology was not available when the decision was made. Look how long in took to improve TV. And there are still people using AM modulated TV using a converter box. I have two. Digital is so much better why was AM used? Again the technology was not available at that time. To sum up your question. It was found that VHF was more useful than HF for normal Com and Nav. The same with Boats Local use VHF is used. For distance travel HF. Now SatCom replaced HF and in many case Cell phone replaces VHF. No more need to call the Marine operator. You even call the Coast Guard on your Cell phone (UHF)  


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Marc Ebelini





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