The preamplifier is very simple. I used a Low Noise integrated circuit manufactured by Hewlett Packard. The device name is MGA86563. It has a Noise Figure of about 2dB and can be used from 0. 5 GHz to at least 6 GHz. The gain is about 20-22dB at 2. 3 GHz. The input and output ports are internally matched to 50 Ohms. All you have to do is to put a ca
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pacitor in front of the device and behind it and provide the necessary supply voltage of 5-7 Volts at the output port. I used a quarterwave stripline for the supply voltage. The 100 Ohms resistor is used to "de-Q" the circuit in order to avoid oscillations. This resistor causes a voltage drop that must be equalized by a somewhat higher supply voltage of 7. 5 Volts. (Fig. 2) The harmonic mixer is not much more than two Schottky Diodes BA481. They short circuit the signal twice at every periode of the LO signal (at every half-wave). At the input there is a bandpass filter to suppress the image frequency. A monolitic amplifier ERA 3 from Mini Circuits (New York) amplifies the signal for another 20dB. This is not necessary in order to have an optimal sensitivity (the preamp would be sufficient without another amplifier) but it helps to have a strong signal at 144 MHz. This allows you to put the converter at the antenna and use a cheap coax cable for the IF. A 144 MHz amplifier at the output is not advisible because strong 144MHz-signals from the neighborhood could get into the amplifier and then cause interference to your 13cm signal. The LC-transformation-circuit at the output makes sure that the mixer is not overloaded by the 50 Ohms of the IF receiver. (Fig. 3) I will not give the circuit diagram for the 1088 MHz local oscillator. It is really not adviceable the way I did it (now I know!). I built a 1088 MHz VCO and...
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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....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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