PA3FWM's Technical Notes

Pieter-Tjerk de Boer, PA3FWM pa3fwm@amsat.org

Since 2009, I semi-regularly write articles for the Dutch amateur radio magazine Electron, under the title "Technische Notities van PA3FWM". Some of these articles focus on a single topic, others address several smaller topics. The topics can be anything technical and amateur-radio related, but tend to emphasize SDR and radio fundamentals. The articles are originally written in Dutch, but since they may be of interest to a broader audience, I try to translate them and publish them here in English.

So far, the following installments are available here:

July 2012 about:
- Single-sideband FM
- Soundcards for SDR
- Capacitance measurement
- Coaxial traps
- Input filter for an active antenna
March 2013, about chirp reception and interpretation
(including some fundamentals of shortwave propagation)
January 2014, about fundamentals of the MiniWhip antenna
(including discussion of directivity of antennas, and a demonstration setup of electric potential measurements)
May 2014 about:
- Exponentially switchable coil, about my design for an inductor that can be varied over a large range, as an alternative to a roller inductor in an antenna tuner.
- Capacitance of antenna elements, about the capacitance of metal rods and plates that are often used as antenna elements in active antennas, such as the MiniWhip.
- High-frequency currents in a printed circuit board; this part was basically a short summary of, and reference to, this very read-worthy document: Mark Fortunato, Successful PCB grounding with mixed-signal chips, http://pdfserv.maximintegrated.com/en/an/TUT5450.pdf, and therefore not translated and reproduced here.
- Alternative use of a sugar cube, about using a sugar cube to remove bits of paint.
February 2015 about:
- WSPR; since this is mostly general information which is available elsewhere, it's not reproduced here.
- Signal/noise ratio of digital amateur modes, explaining the Eb/N0 measure for signal/noise performance, and comparing several amateur modes using this measure.
- Cone-shaped roller inductor.
- Grounding of MiniWhip and other active whip antennas.
July 2015 about:
- Radio propagation during a solar eclipse; see http://wwwhome.ewi.utwente.nl/~ptdeboer/ham/eclipse2015/.
- The Gyrator.
- Integrating signals, and some moonbounce history.
- A ferrite mystery; will be reproduced here along with the solution in the next installment.
December 2015 about:
- A ferrite mystery.
- Measuring small inductances and capacitance with the "AVR transistortester"
- The "Flevo" medium wave transmitting station
- Medium wave musings
- Spiral-shaped variable inductor
April 2016 not yet available
August 2016 about:
- Quartz crystals
- Measuring quartz crystals with the AVR transistor tester
- Arecibo in the Netherlands
- An experimental new digimode: EbNaut
January 2017 about:
- Rain radar on 24 GHz, not reproduced here because it's mostly based on this (in Italian).
- Transformer-coupled source follower in an active antenna
- Smart frequency doubler, not reproduced here because it's essentially based on this.
- Smart passive receiver, not reproduced here because it's mostly based on this.
- Passive FM receivers
- Measuring tape as antenna material
- Common-mode chokes, not reproduced here because it's mostly a summary of this.
- Nano-crystalline toroidal cores
April 2017 about:
- The "kitchen SDR"
- Demonstrating AM sidebands
- Single-sideband jubilees, and SSB with full break-in?
- Silence on 162 kHz
- Taking bearings near a longwave yagi
- Digital noise reduction
January 2018 about:
- Antenna with a French twist
- Solar flare on September 6, 2017
- A Mini-Whip antenna's DXCC score
- Patented RF choke
- Squelch algorithms
- New squelch algorithm for the WebSDR
May 2018 about:
- Relay contacts and "fritting"
- Recent progress in amateur VLF experimentation
- The polyphase mixer used in the Airspy HF+
- Automatic tuning of digital noise reduction
- Musings about a portable LCD TV screen
October 2018 about sideband asymmetry in the Luxembourg effect; not yet available here, but based on this.
May/June 2019 about:
- 1008 kHz QRT
- Selective fading on longwave
- Where did the A, B and C layers go?
- Phase and frequency modulation
- Tubes for phase modulation
- Oscillograms cast in stone
November 2019 about:
- How RTL-SDR dongles work
January 2020 about:
- How does a waveguide work?
March 2020 about:
- Strange resistors
- Radio spectrum at the moon
- Streetlight via the ionosphere
- Norway QRT on 153 kHz, reported earlier here.
- Shielding of a railroad
- The NanoVNA
July 2020 about active antennas; not available here, as it's mostly a review of https://www.dst.defence.gov.au/publication/high-performance-active-antenna-high-frequency-band and a discussion of the (unrelated) antenna I built for the Twente WebSDR, described here.
September 2020 about Noise in FM reception
March 2021 about:
- Which part of a dipole antenna radiates most?
- Near and far fields
July 2021 about Mandelstam's demonstration of sidebands
September 2021 about:
- The ICL7106 voltmeter chip and how to accelerate it
- "Toonfrequent" or ripple control signals on the mains; not reproduced here as it is largely based on my work documented here
- Destructive peak dissipation in a resistor
November 2021 about Oliver Heaviside and the theory of transmission lines
February 2022 about:
- The dim bulb tester
- Amateur VLF activity
- Slot antennas
- Island as an antenna
April 2022 about my ultra-low power continuity tester.
July 2022 about timing of morse code.
October 2022 about thermal noise.
January 2023 about:
- ethernet hardware and its reuse for amateur radio.
- attenuation in cables.
May 2023 about Gilbert cell mixers.
September 2023 about Schematic symbols for transistors.
October 2023 about The Zwischenbasis circuit and its use in active loop antennas.