The uBlox GPS-modules are capable of providing various reference clock signals through the TIMEPULSE pin. By default, this pin outputs a 1 pulse-per-second (PPS) signal. For an upcoming project, a GPS disciplined oscillator (GPSDO), this output had to be adjusted to 100 kHz. Instead of using the manufactuer’s software, u-center, this task is supposed to […]
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Electronics
JFET-based infinite impedance detector for AM-demodulation
The so-called “infinite impedance detector” is a circuit that was commonly used in the old days of vacuum tubes. Since vacuum tubes can be somewhat considered to be heated JFETs, it is evident that such a circuit can also be built using a more modern, silicon-based approach. This article covers my first experiments with a […]
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Total Harmonic Distortion (THD) from dBc
How to calculate THD from dBc This article supplements to my article titled THD Measurement with an Oscilloscope and FFT, which appeared in Elektormagazine [1]. Here I will explain how the formula to calculate THD-F from relative power values (in dBc) was derrived from the standard voltage-ratio formula. A more in-depth explanation of the entire […]
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Generate a stereo-FM multiplex waveform with Python and AWG
Generating more complex arbitrary waveform files for modern test equipment doesn’t have to be difficult. For a recent project, I needed a stereo-FM multiplex (MPX) signal containing two different tones in the left and right stereo audio channels. This article is going to show how to generate such a MPX signal for Siglent SGD-series arbitrary […]
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SITOR-B / NAVTEX Test Signal Generation
This article shows how to generate valid NAVTEX message bitstream using an Arduino. The Arduino implements proper CCIR476 character encoding, SITOR-B forward error correction, synchronization and phasing signals. An entry-level function generator is then used as a FSK modulator on 518 kHz where it can be received by a NAVTEX receiver. UPDATE: There also is […]
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