Author: Sebastian Westerhold

Total Harmonic Distortion (THD) from dBc

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This article supplements to my article titled THD Measurement with an Oscilloscope and FFT, which appeared in Elektormagazine. 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 subject can be found in my research paper titled Total Harmonic Distortion (THD) analysis utilizing the FFT capabilities of modern digital storage oscilloscopes.

Generate a stereo-FM multiplex waveform with Python and AWG

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Time domain view of generated MPX signal

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 waveform generators with Python and PyVISA.

SITOR-B / NAVTEX Test Signal Generation

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The NAVTEX test signal was successfully received on a NAV4 Navtex receiver

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.

VHF LDMOS Power Amplifier Experiments

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LDMOS VHF Power Amplifier Prototype

The NXP MRF101 series high ruggedness N-channel Enhancement-mode lateral MOSFETs promise over 100 Watt CW output power and slightly over 20 dB gain from 1.8 MHz all the way up to 250 MHz. Their mismatch insensitivity for a VSWR of greater than 65:1 without significant device degradation makes these devices extremely interesting for amateur radio operators. While there a plenty of designs for the HF + 6m Bands on the internet, I wanted to see what it takes to use them on the 2m VHF band.

ICS501 / ICS501 VHF Experiments

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ICS501 output spectrum, 15.1 MHz input clock, 90.6 MHz output. Horizontal scale: 2 MHz / division, vertical scale: 20 dB / division

The ICS501 / ICS511 from Renesas are easy to use, fully integrated clock multipliers for output frequencies up to 200 MHz. What makes them particuarly interesting is the integrated crystal oscillator circuit and ability to produce some fractional multiples, such as 6.25 or 2.5. So let’s find out if they’re interesting for the hobbyist who wants to generate clock signals in the VHF range.