A while back, I was asked if I could repair a ODU for a BMS Truck-Coder II. Someone had managed to rip the N connector straight off the casing, including a bit of the microstrip line from the distributed element output filter. See what approach I took to fix the broken stripline. The BMS Truck-Coder […]
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Switched Capacitor (SC) comb filter
Switched-capacitor filters are great alternatives to standard LC filters. Their frequency response can easily be controlled solely by an external clock signal. In this short article we will have a closer look at an extremely narrow switched-capacitor comb filter. For a homebrew EAS (Emergency Alert System) decoder I needed a very selective band pass filter […]
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Review: Abracon Sync’n Go – Portable Precision Frequency Reference
Most professional devices which require high accuracy and precision have an input for some sort of external frequency reference. The frequency 10 MHz is an industry standard particularly for test equipment. Most reference generators are designed for lab use and therefore are bulky and unsuitable for portable use. Abracon now offers a pocket-sized portable solution. […]
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Why you should use high quality soldering tips
That a chain is only as strong as the weakest link should be common sense. Yet I see many people investing into extremely cheap soldering irons and then being surprised about their weak performance. Let’s compare tips of a budget soldering iron and a professional brand soldering iron. A while back I read an article […]
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Modifying a 240V / 50 Hz switch mode power supply for 120 V / 60 Hz
Most switch mode power supplies can handle both 120 or 240 Volts just fine. They usually either have a switch to select the input voltage or are simply designed to cover the whole range to begin with. But what if one needs to operate a switch mode power supply, that is exclusively designed for 240 […]
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JM38510/10901BPA – Military grade 555 timer IC
When parts are being used in military or aerospace applications they need to meet special quality standards. Using off-the-shelf parts is a big no-go and should be avoided at all times. While inventorying all my electronic parts, I stumbled across a few old forgotten parts from a fairly old project which was designed according to […]
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Microcontroller Controlled Police Strobe Light
Circuits with flashing LEDs and amazing color combinations are pretty popular. This is probably because they are not only simple but one can literally see the results instantly. Let’s have a look at a microcontroller controlled police strobe light using an ATtiny45 from Atmel. LED flashing circuits have been around for ages and probably always […]
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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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Direct Sequence Spread Spectrum Experiments
In our digital communication age heavy cryptology becomes more and more necessary everyday to protect our data from eavesdroppers. Direct Sequence Spread Spectrum is one way of covertly transporting data over radio waves. Without the knowledge of the correct code sequence it is nearly impossible for an attacker to decrypt the original message. 47 CFR […]
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Overtone Crystal Oscillator
Crystals with higher frequencies than about 30 MHz are almost exclusively overtone crystals. Such a crystal is intended to be used on an odd multiple of it’s fundamental frequency. Unfortunately, the crystal doesn’t want to resonate on it’s overtone frequency voluntarily, the oscillator circuit needs to force the correct overtone. For a little 2m band […]
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