Which frequency spectrum should not be used for long-range communications?

• A. VHF, UHF, SHF, EHF
• B. LF, MF, HF
• C. VLF, SLF
• D. UHF

Answer: (A)

The main idea here is how radio waves propagate differently across frequency bands. Lower frequencies can travel long distances by bouncing off the ionosphere or by groundwave, letting signals reach far-away receivers without extensive infrastructure. Higher frequencies, on the other hand, are mostly line-of-sight and don’t reflect well from the ionosphere, so their direct range is limited and terrain can block them.

High-frequency bands (the range that includes VHF, UHF, SHF, and EHF) are primarily line-of-sight. They attenuate quickly with distance and don’t rely on reliable ionospheric reflection, so achieving truly long-range, direct communication is impractical without repeaters, towers, or satellite links. That’s why this spectrum is not suitable for long-range links.

Lower bands like LF, MF, and HF can achieve long-range communication through ground wave and ionospheric propagation, while VLF and SLF offer even longer reach with very low data rates. These characteristics make them better suited for long-range use, which is why the high-frequency spectrum is the one to avoid for direct long-range communication.