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What Is an HF Transceiver?

Jean Marie Asta
Jean Marie Asta

An HF transceiver is an electronic device that both transmits and receives radio frequencies between 3 Megahertz (MHz) and 30 MHz. HF stands for “high frequency” and refers to the oscillation rate of radio waves that a transceiver receives and transmits. All radio waves broadcast a frequency between 3 Hertz (Hz) and 300 Gigahertz (GHz). The radio waves also differ in length, depending on frequency. An HF transceiver is used by a wide array of people, including amateur radio operators, military personnel, and humanitarian entities.

Often the HF transceiver will include a manual switch for transmission and reception, coupled to transmission and reception paths on a module, respectively. This switch that has transmission/reception functions connects to three different ports, all containing a common 3 decibel (dB) directional coupler, and a fourth decoupled port that connects to the path designated for reception. The first port and the second port connect to two high frequency power amplifiers on the switch, forming an amplifier that is balanced in the path designated for transmission. A high frequency switch connects to the same two ports, which short-circuits the output in the amplifier that is balanced. The manual switch connects to the reception path and the high frequency switch, which is attached to the transceiver’s transmission path, to selectively alternate between both, making the paths operational as desired.

Woman holding a book
Woman holding a book

Amateur radio stations and amateur radio users often use an HF transceiver. The amateur radio user will often build an amateur HF transceiver of his own, selecting important transmitter and receiver components. In building an HF transceiver, selecting a transmitter is all based on preference, since emitting signals requires hardly any components and little power. When choosing a receiver, it is best to select a receiver that responds to desired tuned stations and rejects any adjacent undesired signals. It is also best to look for mechanical filters that respond well to bandwidths of weak signals and pile-up signals.

To remove interfering signals in an HF transceiver, there are different cascading methods to apply to the device. One method involves shifting the filter’s passband down or up in frequency to the point where undesired signals and noise disappear. Another method to get rid of interference and noise is the process of altering the high/low cut control, which removes the high or low pitch of undesired audio interference from desired audio. Following this method can reduce undesired audio interference, and can even remove it entirely if performed correctly.

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