High Frequency vs. Low Frequency

"Frequency is the number of occurrences of a repeating event per unit of time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency. ----- FMUSER"

Content

1 HF vs. LF
2 Why does low frequency have high energy and high frequency have low energy?
3 What are the advantages of low frequency over high frequency and vice versa?

HF vs. LF

It defines as the number of cycles / second of anything that oscillates and its unit is Hertz (Hz).

Higher frequencies (HF) have a shorter wavelength / closer together which can be highly sensitive to smaller as well as lower conductive. Generally HF do not have good ground penetration in mineralized the ground as the lower frequencies have.

On the other side, Lower frequencies (LF) have a longer wavelength than HF and further apart which definitely makes it more and more sensitive to a higher conductive target. In addition, LF tends to do better in mineralized the ground, but they aren’t as sensitive to small targets.

See Also: >>How to Eliminate Noise on AM and FM Receiver

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There is also one more in this category and it is called as ultra-high frequencies. But it is not used in general purpose and not for human usage to communicate with each other.

The most common are high-frequency (13.56 MHz), low-frequency (around 125 KHz), & ultra-high frequency (860-960 MHz).

Why does low frequency have high energy and high frequency have low energy?
The energy of a wave is not just a matter of frequency. For two waves of the same amplitude the higher frequency will have higher energy content because the medium is vibrating at faster speeds and its particles have higher kinetic energy. 

Frequencies do not add and do not change as waves travel through (linear) media. But waves also have amplitude and amplitudes add up when waves combine. Many little waves can add to become arbitrarily large waves, something surfers well understand. Loud low frequency sounds can have more energy than soft high frequency sounds. A very bright red light can have more energy than a dim blue light even though blue light has higher frequency and therefore is more energetic than red light.

See Also: >>What is the Difference between AM and FM?

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What are the advantages of low frequency over high frequency and vice versa?
High frequencies have more cheaper bandwidth, so it is possible to transfer data at higher speeds.

Additionally, antenna sizes are smaller and have higher gain at higher frequencies.

However, high frequencies, with low power mode, support line of sight propagation mode only, so if you want to send your data over the horizon you need some mediators, such as ground or satellite repeaters.

Lower frequencies support SkyWave or GroundWave propagation modes, which allow data to be transferred over the horizon without any mediators in peer-to-peer fashion. However, antenna sizes are becoming quite large and amount of bandwidth is very limited, so you cannot use it for broadband links.

See Also: >>What is Low Pass Filter and how to build a Low Pass Filter? 

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