For some time, I had been contemplating the purchase of a pocket oscilloscope for up-the-tower or car fixing work. A few months ago I came across this oscilloscope listing on eBay. It was from a Canadian seller called "nooelec". The unit is a JYE DSO 082. It is a single channel, 10MHz bandwidth, 50Ms/S sample rate, LCD display digital storage oscilloscope. The specifications looked promising, so I went ahead and ordered one.
You must have already bought a radio or test equipment that had a display window with scratches. Or maybe you have scratched it yourself? Well, be aware that there is a simple solution to removing scratches off the surface of clear hard plastic. Light scratch marks will disappear and deeper ones will be much reduced.
You and I know that nothing is perfect in this world and the world of electronic instrumentation is no exception! It is therefore important to ensure that our measuring instruments are as accurate as possible.
One of the most likely test instrument to deviate over time is the frequency counter. The reason is that it uses the precision of an internal reference, an oscillator crystal usually running at 10,000 MHz (to verify this, look for a "10.0000" on a crystal or on a small metal box inside the counter). However, this oscillator "ages" over time, and thus changes in resonant frequency. Fortunately in most cases, this oscillator is adjustable. There is usually a "small screw" adjustment (a variable capacitor) on or near the oscillator. But where to get a reliable 10MHz reference oscillator to adjust the counter? Yes, fans of shortwave radio, the WWV station! This atomic clock at NIST (USA) transmits its signal on a carrier frequency of exactly 10.0000000 MHz.