For uncompressed speech a typical SSB peak to average power ratio is 14 dB. The average power of a typical single sideband signal is much lower than the peak power. His study was prompted in part by low transmitted average power levels. The article, Audio Processing and ALC in the FT-897D (pdf), describes his research and gives advice on optimum microphone gain and processor settings. Martin Ehrenfried, G8JNJ, is an electrical engineer who has written many excellent articles on ham radio topics. He also has hands-on experience with Icom 756PRO-series radios of his own, and he was kind enough to answer my questions about ALC. He has listened to the signals of hundreds of hams while helping them set up their radios and his products. Julius Jones, W2IHY, and his company W2IHY Technologies, produce high quality audio equipment designed to work with ham radios. The article does not apply to digital modes, such as PSK31, that are more sensitive to nonlinearity from ALC action than are voice modes. The final section summarizes access to ALC meters for blind and vision-impaired hams. This article summarizes practical advice about using an ALC meter from two experts on amateur radio signal quality. You might be tempted to operate at the top of the range for a more powerful signal, but the signal quality may suffer. It's not as easy when the recommended range on the ALC meter is wide. The Elecraft K3, Flex Radios, and Yaesu FT DX-3000D are good examples. The key is knowing how to use the ALC meter.Ĭhoosing an optimum amount of ALC activity is easy if the radio manufacturer tells you the ideal ALC meter reading. This article is about how to operate a transmitter at the optimum point-where the average signal level is as high as possible without noticeable distortion or interference. It keeps the amplifier input in the designed range for linear operation.ĭepending on the ALC circuit design and how hard it is driven (by the microphone output level and mic gain setting), the ALC circuit can distort the signal and cause interference. An Automatic Level Control (ALC) circuit governs the signal strength going into the power amplifier in a ham radio transmitter.
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