A SHORT WAVE REGENERATIVE RECEIVER


Posted on Feb 6, 2014

Sensitivity and selectivity are issues that will invariably concern a short wave listener when he wishes to purchase a new receiver. Commercially available communications equipment will undoubtedly fulfill his expectations, but we are talking here of highly priced products. Low-cost alternatives call mainly for homebrewed radios, and in this sense


A SHORT WAVE REGENERATIVE RECEIVER
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, the regenerative receiver is the common choice due to its simplicity, low parts count and very acceptable performance. The author is also a short wave enthusiast and for some time used his family`s Philips MW/SW vacuum tube radio. Later, he changed to a solid-state Sony ICF-7600, a high selectivity receiver featuring ceramic filters in the IF stages. Then he would discover how much fun he could have building radios on his spare time. After testing a variety of schematics available in books and on the web, the author finally decided to make his own designs. Back in 2003, an experimental Colpitts-type shortwave regenerative receiver was made public on the web by this servant. It was reported to tune from the 22-meter band up to the 11-meter band with a single set of coils. Operation was found to be satisfactory with the prototype built on a protoboard and a ground plane fixed underneath. Further work with the receiver using different sets of coils revealed a larger usable frequency spectrum. Fig. 1 shows the schematic diagram of an improved version of the early receiver. It will tune signals from 3500kHz up to 26MHz, roughly in three bands, each with a 1. 96:1 frequency-ratio. It must be quoted that the said frequency ratio is what the author got for his prototype. It is a function of the maximum-to-minimum capacitance of the variable tuning capacitor and the stray capacitance of the circuit layout. The Colpitts approach...




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