ANTENTOP- 01- 2010, # 012

Some Thoughts on Regenerative Receivers

One of Armstrong Regenerative Receiver

Credit Line: Thermionic Tubes in Radio Telegraphy and Telephony, by: John Scott- Taggart, The Wireless Press LTD, 1921

 Effectively increases the "Q" of the tuned circuit by the concept of "negative resistance." Any circuit that accomplishes this will do the trick. Typically, an oscillator circuit, such as a Hartley, Colpitts, or the like is chosen. One then sets the loop gain of the oscillator circuit by some means to be just below the point of oscillation. Later, it will be seen that there are some clear design advantages to some circuits over the others.

Runs in "oscillation" mode, if desired, to act as a direct conversion or autodyne detector for CW or Single Sideband signals. The oscillation mode provides the BFO, or course.

The workings are not dependent on vacuum tubes versus transistors. The real problems in any design at least, are:

1. Interaction with the antenna, and QRM generated by the receiver itself. "Grounded Grid" or equivalent isolation amplifier does the trick here. An un-tuned grounded gate FET amplifier seems to be the modern choice.

2. There is massive interaction with tuning as a function of regeneration setting. If there is a way to separate detection from regeneration, this problem can be addressed. One typical vacuum tube design uses a Colpitts oscillator in parallel with a plate or grid leak detector (my favorite for vacuum tube designs). Another alternative (my Senior EE project in 1960!) was to insert a cathode follower between the tuned circuit and the detector/feedback vacuum tube).

Edwin H. Colpitts, "Oscillation Generator,"

U.S. patent 1,624,537 (filed: 1 February 1918: issued: 12 April 1927)

Figure Credit Line: Wiki

http://www.antentop.org/

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