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* is a superhet with only two NE602s? * has no discrete transistors? Can't guess? The answer is the "38 Special". The "38 Special" is an exercise in minimization. We feel that it is "special" because of the following: *It works on the under-utilized 30M band *Runs of f a 8V supply (due to limitations of some components) *Excellent price/performance ratio *Last, but certainly not least, the fact that it offers a great platform for another year of hacking... The "38 Special" is the result of an effort which started with hacking the 40-9er transceiver. A novelty radio, the direct-conversion 40-9er was quite limited, especially for weak signal work. The "38 Special" rectifies most of these problems and even adds a few nice features. It came to life due to the design contest challenge and the never ending enthusiasm and encouragement by Doug, KI6DS, who also came up with the great name. The "38 Special" is a superhet transceiver for the 30M band. The first thing you'll notice looking at the schematics is the lack of discrete transistors. I have been playing with this concept for some time and the 38 Special was the right vehicle. The transmit section relies on a TTL buffer. I extended this concept to utilize the same TTL chip for other tasks. Although it's an NE602-based superhet transceiver, the "38 Special" incorporates only two NE602s. I reuse the product-detector as the transmit mixer by channeling different signals to that chip on receive and transmit. Also, the traditional LM380/386 is gone in favor of a more versatile dual op-amp circuit for the audio section. (please look at our rules and privacy policy) |
e.silva@machine--tools.com (Eunice Silva) for additional information. This email is used for forwarding to newsgroup user.
