Little spy bugs and tracking devices are generally very popular circuits in the electronics community. This is probably because the user gets to feel like James Bond and other special agents for a while. Let’s have a look at a simple tracking device. Spy bugs and tracking devices are not only very popular in the […]
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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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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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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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L-Network impedance matching
Impedance matching is an everyday problem for RF circuit designers. The L-Network is one of the easiest lossless ways of matching a low source impedance to a higher load impedance. This article shows how they work and how to design them. Matching a transistor amplifier’s low output impedance with the higher impedance of an antenna […]
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Review: Abracon ABFT Frequency Translators
In March, 2012, Abracon announced the production of ultra-low jitter, VCXO based frequency translators / jitter attenuators. This is supposed to resolve some problems that accompany classic PLL-based designs at an affordable price. Now, the ABFT frequency translators / jitter attenuators are available on the market and it’s time to have a closer look. The […]
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Blown Capacitors – Repairing LCDs and TFTs
Blown capacitors have been around as long as capacitors themselves. Replacing defective capacitors is something every electronics engineer should be capable off. Let’s have a look how to turn a broken LC Display back into a functioning device. Free TVs and computer screens are almost literally laying on the side of the road. About a […]
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Crystal controlled listening device
There are tons of circuits for listening devices available on the internet. For the most part, they all have in common that they are virtually useless. This article shows how to build a reliable, small and inexpensive listening device using a PLL clock multiplier and a standard crystal. Most audio listening devices, also called spy […]
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Pseudorandom Number Generator (PRNG)
The core of any spread spectrum (and other cryptographic) system is a pseudo random number generator (PRNG). Pseudo random numbers play a big role in the world of electronics and cryptology. The quality of a spread spectrum link and its properties strongly depend on this device. For my Direct Sequence Spread Spectrum Experiments I needed […]
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