![]() ![]() The rectifier-integrator has been changed to a straightforward two diode rectifier arrangement that has been used in previous receivers. This gives a total gain of about three thousand which is generally enough for our purpose. The second amplifier has a fixed gain of about thirty. The first amplifier is set up with a variable gain of zero to one hundred. The new circuit uses the two amplifiers on the IC with capacitor coupling. The amplifier function is quite different from the original precision rectifier arrangement. The original 1436 quad op-amp was not easily available. ![]() Another advantage here is that I have selected the TLO82 dual biFET op-amps which are available from Radio Shack. The two op-amps are separated on the circuit board to minimize interaction. In this new circuit design, I have separated the two functions by using two dual op-amps in place of the original quad op-amp. It occurred to me that the problem could very well be a result of the gyrator tuning function of the circuit being too close in proximity to the amplifier function, inasmuch as both functions are on the same integrated circuit chip. Some users of that receiver have problems with the receiver going into oscillation when the gain was increased to a high level. Many of the receivers have been built and used successfully for monitoring SID's since 1994. The original gyrator tuned VLF receiver has been previously published 1, 2. Gyrator II - An Improved Gyrator Tuned VLF Receiver ![]()
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