Here is a quick project I made one weekend. I had just gotten my new toys, a Rohde & Schwarz FSIQ 7 GHz spectrum analyzer and two R&S SME 03 signal generators. I wanted to make something where I could employ my new test gear, so I decided to make a microwave noise source. The noise source is quite simple. It has a reverse biased AT41486 RF-transistor and the noise due […]

I’ve had the need  for a high-voltage differential probe for a long time. Mainly for probing mains connected switch-mode power supplies and such. I looked in to buying one but they are fairly expensive for what they are. You can get 25 MHz bandwidth Chinese ones for around 150 € but anything from Agilent/Tektronix/Fluke will quickly run up to multiple hundreds. I looked in to making one and they seemed […]

I was slightly concerned about the contact resistance of the 10->8 mm brass compression fittings in my induction heaters tank circuit. Out of curiosity I measured the resistances in my tank circuit. I thought I’d make this small post about how to measure very low resistances. This might be fairly obvious to someone but it still bears mentioning. The easiest way to measure very low resistance is by passing a much […]

I had the need to test the saturation current of some inductors I had wound. I built this pretty simple tester for testing the saturation current of inductors. It seems to work pretty well up to about 100A or so. I had a switch-mode power supply (48V to some lower voltages at around a kW or so, from telecommunications equipment) laying around that had a lot of components (FETs, power […]

I’m currently building an induction heater. I’ve already built one controller based on an analog PLL so this time I decided to go all digital and use an ARM Cortex-M4 microcontroller (STM32F303). For this I needed to implement a digital phase-locked loop running on the MCU. Principle An ADPLL is basically an analog phase-locked loop but implemented in software. You take the phase difference between a reference signal (the one […]

This is a project I made quite a while back (about 7 months ago). I wanted a bigger display for a project of mine and noticed that PlayStation Portable displays (480×272 pixels) are quite cheap on eBay but they do not have an integrated controller/display driver. It seemed like a perfect project to practice using FPGAs so off I went. The PCB is a 4-layer design containing an Altera Cyclone […]

I am currently building an FMCW radar. I do not have all the parts finished so I made a doppler radar from the parts I had on hand. Theory Basically a Doppler radar is a type of radar which measures speed of objects in front of it. The transmitted signal is mixed with the received frequency in a frequency mixer. If an object moves in front of the radar, the received […]

I recently saw a post on Hackaday about a course in MIT where the students get to build an FMCW radar from mainly off-the-shelf components. I got pretty excited about it and immediately thought that I wanted to build a better one from scratch. The design presented in this post is just the preliminary design, a lot of things might change as I go along. Theory I won’t go to too much detail […]

I had some space left on a PCB panel I was ordering so I quickly whipped up a return loss meter based on an AD8319 logarithmic detector from Analog devices. The AD8319 is specified up to 10GHz. The circuit has a 10dB attenuator and a resistive SWR bridge which output is measured (differentially) with the log detector. The circuit is laid out on 0.8mm FR4 PCB with impedance matched microstrip transmission […]

Categories: Electronics projects, RF

I wanted to listen to HF bands using my RTLSDR USB dongle. Since the RTLSDR dongle can only receive from around 64MHz upwards I needed an up-converter which converts the HF band (0-50MHz) to a higher frequency I can receive with my dongle. The converter will work up to about 70MHz. Many of the available converters seemed quite pricey and not too well designed (no filtering on the local oscillator […]