# oscillator mcpos400 plus

Posted on Feb 4, 2014

This is a UHF oscillator circuit I designed to make use of the Mini-Circuits POS-400+ voltage controlled oscillator chip. By giving it a voltage from 0 to 12V on pin 8 it gives out a sine wave ranging from 200MHz to 380MHz on pin 2, though my testing with a lecher line gave a range of 200MHz to 440MHz. The purpose was to use it as a frequency sour

ce for the testatika Linden experiment under the assumption that the experiment`s long wire is a lecher line that is 1 metre long, the wavelength corresponding to 300MHz which in turn corresponds to the speed of light (approximately 300, 000, 000 metres/second. ) Basically I needed two 12VDC sources, one fixed at 12V for feeding pin 1 and one that could vary between 0 and 12V for feeding pin 8, the latter for selecting the frequency (from 200MHz to 380MHz. ) Unfortunately I didn`t have two 12VDC sources where one leg of each was connected to ground. I had a power supply that I`d built where that was the case but everything else I had had both legs floating as far as I could tell. So somehow I had to come up with a circuit that would allow my one power supply to provide both fixed 12VDC and variable 12VDC. I came up with the following circuit. It uses the fact that a single 12VDC source can be made into two separate ones by use of two parallel lines (the top and bottom horizontal lines connected to the positive leg in the above), the voltage supplied to both being 12V but the current being divided, which I didn`t care about since I had enough current. For the variable line I used the fact that voltage drops across a resistor, the bigger the resistance the bigger the voltage drop. Since I needed various voltages I used a potentiometer for the resistor (a potentiometer is a variable resistor. ) That way I could choose the size...

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