On February 5th, 2015 the electronics retailer RadioShack finally filed for Chapter 11 protection under US bankruptcy law after 11 consecutive quarterly losses. Many stores closed as a result of this. Before they closed their doors forever, RadioShack blew out their remaining inventory with great discounts. When I first heard of the RadioShack bankruptcy, I […]
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DIY: Adjustable 30 kV High Voltage Power Supply
High voltage power supplies can open interesting doors to research topics such as laser, x-ray, spark gap transmitters. And many other specialized niches. Unfortunately, laboratory grade high voltage power supplies are rather costly. Luckily, there is a much less expensive way to put high voltage experiments into the hobbyists reach. This article shows how to […]
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Diplexer with integrated Bias-T (Triplexer) for QO-100 and X-band microwave reception using LNBs
This article shows how to build a simple Triplexer (Diplexer plus integrated DC Bias-T) for use with commercial TV LNBs for QO-100 or X-band microwave experiments. Introduction When using modified, commercial LNBs for reception of the QO-100 amateur radio satellite or X-band microwave experiments, it is necessary to pass a clock-reference signal, a DC supply […]
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DSP Diode Clipping Algorithm for Overdrive and Distortion Effects
This article shows how to approximate the behaviour of a regular diode in a mathematical equation and how to subsequently implement the behaviour in software. The DSP algorithm can be modified to implement different topologies, such as single diode clipping, dual diode symmetrical soft clipping or asymmetrical clipping. The easiest way to implement distortion through […]
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Critical length of a PCB trace and when to treat it as a transmission line
Ideally, the impedance of PCB traces should be matched to the load and source impedances. This becomes especially important in high-frequency and high-speed digital PCB designs. Various rules of thumb are available to determine the critical length at which a PCB trace should be treated as a transmission line. Below this critical length, an impedance […]
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Universal Clock Translator using Renesas VersaClock 6E Devices
Due to the popularity of the QO-100 geostationary amateur radio communication satellite, precision GPS reference frequency sources (GPSDO) are becoming more and more common in home labs. The desire to derive different, fixed frequency signals from a GPSDO has similarly been increasing as different devices requiere different reference clocks with different frequencies. Therefore, this article […]
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LNB Modification for 10 GHz QO-100 Satellite Reception
This article shows how to modify an inexpensive LNB to accept an external LO-reference signal in order to be used as a K-band downconverter for QO-100 (Qatar Es’hail 2) amateur radio sattelite reception, radio astronomy or similar K-band experiments. This article is a shortened version of a scientific paper that I wrote as the lead […]
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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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First PCB Manufacturing Run with Dirty PCBs
In an earlier article I gave an introduction to DipTrace and in another article I showed how to correctly export a layout files for the PCB manufacturing service Dirty PCB. Besides familiarizing myself with DipTrace, I also used the articles as a chance to test Dirty PCBs. I have never used that service before. As […]
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Video Distribution Amplifier | 10 MHz Reference Distribution
Three Sigma VDA-100 Video Distribution Amplifiers (DA) have been sitting on my shelf for a while. The DAs have been waiting to be repurposed for something useful. When Jackson Labs sent me a custom variant of the FireFly-IIA GPS-Locked double ovenized 10 MHZ reference oscillator, I decided to repurpose one of the VDA-100 as a […]
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