The simple crystal oscillator is subject to Those last threeĮxamples offer very good long-term stability, meaning that they can be set up and left alone for years. 10 MHz is commonly used, and might beĭerived from a simple crystal oscillator, an oven-controlled oscillator, a GPS-disciplined oscillator, or a rubidium frequency standard. The easiest way to generate an accurate 1 kHz signal is to divide it down from some higher, well-known frequency. You are running will display correspondingly different frequencies unless you compensate for the error. For example, an error of 0.2Hz at 137 kHz might be 0.27 Hz at 185 khz. Offsets may be different for different frequency bands. Any errors in conversion oscillators or the BFO will produce offsets from the expected frequency. In USB mode, it would be the difference between the actual transmitįrequency and the dial frequency of the receiver. Receiver audio frequency: Whether your receiver is set for CW or SSB, you expect a certain audio pitch when it is tuned to Times keep changing, then the program becomes "deaf," only decoding strong signals. Particularly in programs like WOLF, copy is built up over time by adding frames of data. Recording functions, but in our world, reliable clocking is necessary both to display very accurate frequencies, and to assist in lining It could easily be above or below that by a few Hz. The real sampling rate is exactly 11025.000 Hz. Due to tolerances in timing within the computer, it's unlikely that As an example, 11025 Hz is fairly common. Either you or the programĬhooses a nominal sampling rate. Sampling Rate: Let's say you are running a DSP program such as ARGO, Spectrum Laboratory, etc. Explanations of the need for these calibrations: Just about any audio frequency could be chosen, as long as it's known.īut having 1kHz markers on a receiver is especially convenient. It can also be used for calibration markers on a receiver. Sound card sampling rate measurements, and if that 1 kHz signal has a fast risetime with harmonics up into the radio spectrum, A very accurate 1 kHz audio tone can easily be used for With Loran-C shut down in North America, another approach is needed. Where Loran-C on 100 kHz is still active, these calibrations may be done by methods for Some of the techniques used for weak-signal reception in the LF and lower MF range require accurate calibration ofĪudio frequencies from the receiver and the actual sampling rate of a computer's sound card. Sampling Rate and Receiver Calibrator for LF/MF Work
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