![]() ![]() The type of signal being transmitted will determine the bandwidth needed at the In the latterĬase, the clarity of weak signals can be improved by using various filters, such as bandwidth controls.ĩ. To be increased when receiving weak signals, despite this increasing background noise. ![]() Received without distortion and with low levels of background noise. The sensitivity reduces both the signal and the background noise. IfĪ received signal is particularly strong it may saturate the RF stage and thus be distorted. The sensitivity control acts on the RF stage of a receiver. The required frequency is set by turning selector knobs until the desiredįrequency appears in the indicator windows. However, on other equipments the following modes may be selectable: Some devices operate only on the upper sideband and have no other modes. Automaticįine tuning takes place during the first 0.5 seconds of each transmission. Systems include a warning light which extinguishes when tuning has been accomplished. Failure to resonate produces a 1 kHzĪudio warning tone which will continue to operate until the frequency has been reselected. Place and, in some systems, this causes the tuner to resonate. During the tuning cycle, coarse matching of transmitter and aerial takes The aerial tuning unit, or coupler antenna, matches the transmitter andĪntenna to ensure efficient radiation of maximum power from the aerial. ![]() Some multi-crew aircraft it may be at a rear station.Ĥ. The control unit will normally be installed in the cockpit although in Spacing is in the order of 100 Hz intervals (giving 280,000 channels) with some older equipments more Sideband (SSB) mode but may be able to operate in double sideband (DSB) and CW modes. Typically an HF set is able to operate in the 2 – 30 MHz range, usually in the single The control unit enables selection of the frequency and mode of operation of theĮquipment. Typical HF Installationįig 1 illustrates, in block schematic form, a typical aircraft HF installation. This chapter describes the installation and operation of a typical HF communications system andīriefly mentions the uses of MF and LF systems. AP3456 – 7-1 - LF, MF and HF Communications CHAPTER 1 - LF, MF AND HF COMMUNICATIONS Introduction ![]()
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