The Precision VXO (PVXO) and its matching Crystal Test Fixture (CTF) were created to provide a low cost means of evaluating the characteristics of crystals and a means of measuring their series resonant frequency. With this information, one can then build very low cost, high performance, crystal filters for receivers and transmitters. The PVXO was
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kitted by the NJ QRP Club, but has since sold out those units. However, photos of that unit are available on this page for completeness. The schematic diagram for the PVXO. A detailed description of what this circuit is and how it works can be found in the Atlanticon 2002 paper entitled "Simplified Tools and Methods for Measuring Crystals" whose link is at the bottom of this page. The circuitry shown above is transformed to a working instrument using Manhattan-style construction. The front panel contains the frequency control potentiometer, inductance switches, and the output BNC connector. Later on in the development of the instrument, the Arizona QRP Club offered their inexpensive "Stinger Singer" CW frequeny readout designed by Dan Tayloe, N7VE. This module was added and the instrument could now read out the frequency to which it was set. A SPST push button switch was added to the front panel to control the module. The NJ QRP Club sold 100 of the PVXO kits during 2002 and 2003. This picture shows what the finished kit looked like. Included were all components, case, and templates for doing the lettered covers. This kit was relatively expensive to produce due to the cost of the components, especially the precision 10 turn pot, five switches, and case, and therefore didn`t sell very well. However, those that bought them got a real deal considering the capabilities of the unit. This is a spectrum plot of the PVXO with a 4....
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The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
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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