While working two-meter SSB from the Benson area, I decided that local terrain and the limited height of my home-made six-element yagi, necessitate I incorporate a high gain antenna pre-amplifier at it`s terminations to enhance receiver signal strength. This approach would give that little extra advantage to help dig the signals out of the noise levels. I knew
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that this method would produce superior results, compared to a pre-amp located close to the transmitter at the other end of the transmission line. Unfortunately, this approach requires that the pre-amp be protected from the high power being fed from the finals in the transmitter to the yagi. In my case it was a 160 watt output `brick` driven from a Kenwood TR-9000 all mode transceiver. Consequently, the pre-amp needs to be switched out of the line during SSB transmission. There are a number of schemes/approaches for doing this task. The most common uses an rf switch (senses minute amounts of rf during initiation of the transmission phases and activates a relay to place the pre-amp off line). Unfortunately, there are many examples of failure using this technique to really protect the pre-amps reliably. Case in point. many `brick-amp/pre-amp` combos available to the ham community suffer from blown pre-amps. There are some expensive sophisticated power management/switching devices available, but again cost can be a factor incorporating them into the average `Joe`s` ham shack budget. I conducted a detailed search on the net for a low cost approach, and couldn`t find a suitable project, thus the unit which I came-up for my needs is presented herein. As with all prudent projects, the old scrap/salvage box becomes a key player in the design, and this endeavor is no exception. My approach to make a simple timing circuit uses...
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Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
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The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
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