Circuit RF Amplifier


Posted on Feb 5, 2014

One of the best RF amplifiers ever published was Wes Hayward`s post mixer amplifier in the Progressive Communications Receiver. It quickly became known as a great high level RF amplifier. With a standing current of 50ma, it takes a very strong signal to upset this amplifier. Check out page 15. 24, figure 15. 33 of the 2000 ARRL Handbook for Radio Amateurs for more information.


Circuit RF Amplifier
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This receiver is designed to work in the worst conditions that many hams have to tolerate: living in a condo or townhouse with antenna restrictions. A Hamstick antenna mounted just inside a bedroom window (in a townhouse) was used to test the sensitivity of the receiver. A 16-18dB RF amplifier was used to provide the necessary sensitivity to work with a hamstick in a townhouse/condo. When this receiver is used with better antennas, the front end gain needs to be "tuned" for the antenna system used. The RF amplifier needs to be bypassed in really good antenna systems, and maybe used only on the 17 meter band. Instructions for bypassing the RF amplifier are near the bottom of this page. The right amount of gain is a compromise between sensitivity and dynamic range. When using a Hamstick, signal levels are so low that going all the way for sensitivity gives a very good performing setup. An excellent article that shows the effectiveness of using Hamsticks in a dipole configuration is "Receiving Antennas", by Robert L. Nelson, K6ZGQ, Ham Radio, May 1970, pp 56-63 (Subtitled: "A discussion of special purpose antennas for receiving - including some novel ideas for improved performance on the lower bands"). Mr. Nelson states, from the article above (page 62), "I have obtained good results with both a helical dipole and an untuned five-foot-long dipole with a capacitive hat when worked through an antenna coupler. However, the...




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