Probably any person interested in RF knows the basic concept of frequency (FM) and phase modulation (PM) as the terms are pretty much self self-explanatory. Yet when it comes to the practical implementation, I frequently notice how little the properties of both modulation techniques are actually understood. From my experience, a vast majority falsely believes […]
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Search Results for: Phase modulation
Quick look at a BPSK31 signal
PSK31 is gaining more popularity among amateur radio enthusiasts. It’s extremely small bandwidth and excellent performance in weak signal conditions make this mode perfect for low power HF stations. PSK31 is a digital transmission mode with just about 31 Hz bandwidth. The signal conveys data at a data rate of 31.25 baud and is extremely […]
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Closer look at a Direct Sequence Spread Spectrum Signal
This article is going to take a closer look at the properties of a pseudo random bit sequence and a simple direct sequence spread spectrum signal both in the time- and frequency domain using the FFT capabilities of a Teledyne LeCroy WaveAce 1002. A while back, I posted an article about a Pseudorandom Number Generator […]
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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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LeCroy WS3162 and HDO4024 Bugs
Exposing some bugs on LeCroy’s new WaveStation 3162 and the HDO4024 oscilloscope. Bug 1 (WS3162): When modulation is applied to a channel, the amplitude drops below the set value. Bug 2 (WS3162): Phase control dysfunctional on both channels when modulation is applied to either one channel. Bug 3 (HDO4024): Spectrum calculation locks up and slows […]
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Why PSK31 over FM is nonsense
The current issue of ARRL’s magazine QST features an article about PSK31 on 2m in FM. This article is going to show why this is an unnecessary waste of bandwidth and therefore nonsense. PSK31 is a digital transmission mode designed for minimum bandwidth and great performance even in weak signal conditions. Sending a PSK31 signal […]
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DSSS / BPSK Clock Recovery with the Abracon ABFT
Clock recovery in Spread Spectrum applications and BPSK modulated signals can be somewhat tricky. There are no commercial solutions available solely for this task either. Or are there? This article shows a great off-label use of the Abracon ABFT. Clock recovery in a Direct Sequence Spread Spectrum (DSSS) receiver can be quite a challenge. Because […]
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How it works: Quadrature detector
Many integrated FM quadrature demodulation circuits, such as the MC3361 or MC3362, have a defined LC tank circuit that creates a specific phase shift of 90 degrees at the center frequency of the demodulator. Let’s take a closer in depth look at how they work. A quadrature demodulator for FM signals consists out of two […]
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No Tune NE602 / NE612 FM Demodulator
FM demodulators have and always will be desired circuits. Many circuit designs use old and obsolete parts or appear to be too complicated for beginners. This design shows a very simple FM demodulator, a quadrature demodulator to be precise, for a 455 KHz IF using only a handful of parts and an NE602. The NE602 […]
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