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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VHF LDMOS Power Amplifier Experiments
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 […]
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ICS501 / ICS501 VHF Experiments
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 […]
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Arduino |Automatically Save Variables to EEPROM on Power-Down
A recurring challenge for Arduino projects is that variables are volatile and will be lost completely unless previously stored to some sort of non-volatile storage such as de inbuilt EEPROM. This article shows a minimalistic approach to detect sudden loss of power and automatically store a variable to an EEPROM adress. First I should mention […]
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Diamex Prog-S2 | Arduino IDE
The Diamex Prog-S2 is an universal USB ISP programmer vor various microcontrollers including Atmel AVRs. This article shows how to integrate the programmer into the Arduino IDE There are a few articles on the web that talk about the Diamex Prog-S2 and Arduino. But it seemed to me like they were either outdated or faulty. […]
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Automated Forward Gain Measurement
This article is going to take you into the world of automation. Using MATLAB and commercial off-the-shelf bits and pieces, this article will show how to measure the forward gain of a RF device. For a long time now I had a bunch of Mini Circuits portable test equipment bits and pieces sitting around. S […]
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