Electronics and other subjects I happen to write about
Placing the ground radials of the monopole antennas usually used with 80 m fox hunting (radio orienteering) transmitters such that the runners do not risk getting entangled in them is time consuming. So it would be good if it were possible to eliminate these radials by instead using dipole antennas. There is a design published Continue reading Sleeve Dipole for 80 m Fox Hunting Transmitters
By Per Magnusson, SA5BYZ This is the sixth part in the article series about the FoxScope 2m ARDF receiver and describes how it is used. It is assumed the reader knows how radio direction finding in general is done on the 2 m band. The receiver has an alphanumeric LCD, a rotary encoder with a Continue reading FoxScope 2m – 144 MHz ARDF Receiver – Part 6 – Usage
By Per Magnusson, SA5BYZ The receiver is mechanically based mostly on 3D-printed parts. The antenna is described in a previous article, so this section focuses on the mechanics of the receiver itself. The 3D models can be downloaded via the following link: Link to a zip-file with the files: I printed most of the parts Continue reading FoxScope 2m – 144 MHz ARDF Receiver – Part 5 – Mechanics
By Per Magnusson, SA5BYZ In addition to the RF and processor boards described in previous articles, there are three simpler boards that make up the electronics of the receiver. The following files are available for download: Link to a zip-file with he files: LCD Board The LCD board is very simple. It essentially just contains Continue reading FoxScope 2m – 144 MHz ARDF Receiver – Part 4 – Other…
By Per Magnusson, SA5BYZ This is the third part in the article series about the FoxScope 2m ARDF receiver. The processor board contains (surprise) the processor, the audio codec, the LiPo charging circuit, voltage regulators and various external interfaces. The following files are available for download: Link to a zip-file with the files: Software The Continue reading FoxScope 2m – 144 MHz ARDF…
By Per Magnusson, SA5BYZ This is the second part in the article series about the FoxScope 2m ARDF receiver. The RF board contains the RF-attenuator/amplifier, local oscillator, mixer, IF-filter and the IF amplifier. It has an SMA connector for connecting to the antenna and interfaces with the processor board via a 32-pin, 0.5 mm pitch Continue reading FoxScope 2m – 144 MHz ARDF Receiver – Part 2 –…
By Per Magnusson, SA5BYZ This is the first in a series of articles describing a 2 m (144 MHz) direction finding receiver for “fox hunting”. I have built a few of these for myself and for friends. The receivers have been used on events starting in 2025, including the ARDF World Championships in Lithuania. The Continue reading FoxScope 2m – 144 MHz ARDF Receiver – Part 1 – Overview
I have previously published two versions of a 3D-printed tape measure Yagi antenna design for fox hunting on the 2m band (144 MHz): This article presents some slight improvements over the previous designs. The handle is less complicated and lighter and there is better protection for the elements from getting kinked. A drill guide for Continue reading 2 m Fox Hunting Antenna v3
Den här artikeln publicerades först i QTC nummer 2 2025. Programkod, filer för kretskortstillverkning och 3D-modeller för den färdiga sändaren finns på https://github.com/per-magnusson/RP2350-Foxoring-Transmitter. I del 1 av den här tvådelade artikeln [1] beskrevs hur man från en Raspberry Pi Pico 2 (ett billigt litet mikrokontrollerkort) direkt kan skapa häpnadsväckande bra HF-signaler som bara…
En resa mot krångligare mjukvara för attmed minimalistisk hårdvara få fina RF-egenskaper Den här artikeln publicerades först i QTC nummer 1 2025. Programkod, filer för kretskortstillverkning och 3D-modeller för den färdiga sändaren finns på https://github.com/per-magnusson/RP2350-Foxoring-Transmitter. Texten här i del 1 beskriver hur mjukvaran fungerar och utvecklades mot att generera allt bättre…
Back in 2023, I published a 3D-printed tape measure Yagi antenna design for fox hunting on the 2m band (144 MHz). While the antenna worked (and still works) fine, I realized that it would be better to have the tape measure pieces mounted with the broadside towards the front rather than up. That way, they Continue reading Improved 2 m Fox Hunting Antenna
Många rävsaxar/pejlmottagare för radiopejlorientering är konstruerade så att de slås på när man kopplar in hörlurskontakten. Denna hörlurskontakt är åtminstone på mottagare från OK2BWN av typen 5-polig DIN, medan normala konsumentlurar av olika slag vanligtvis har en 3,5-mm TRS- (tip-ring-sleeve, utan mikrofon) eller TRRS-kontakt (tip-ring-ring-sleeve, med mikrofon). För att få de två att passa…
I needed a small and inexpensive 3.3 V alphanumeric LCD for a project and found the 2 8 character RC0802A-TIY-ESV sold by tme.eu. I ordered a few but had a very hard time getting anything to display on it. This blog post describes the solution and how I found it. The LCD has ST7066U as the Continue reading Fooled by a Blatant Error in the RC0802A LCD Datasheet
When doing frequency synthesis with fractional-N PLLs, one often needs to find a rational approximation of a floating point number with the constraint that the numerator must not be larger than a certain number. The more exact the approximation is, the closer the actual frequency will be to the desired one. The integer part is Continue reading Fast Algorithm for Rational Approximation of Floating…
I maintain a set of simple ARDF (amateur radio direction finding, or fox hunting ) receivers of the type Compact 3,5F from OK2BWN for use by beginners. A problem with some of the receivers is that the gain cannot be set low enough, which means that the audio becomes unbearably loud close to a transmitter. I Continue reading Reverse-Engineering the OK2BWN Compact 3,5F ARDF Receiver
Den här artikeln publicerades först i QTC nr 5 2023. Via SM0GNS Peder fick jag tag på en ganska komplett byggsats för kretskortet till en ROX-2X radiopejlmottagare [1] för 2-m-bandet. Antagligen hade Peder tröttnat på att jag lånat färdigbyggda mottagare av honom och tyckte det var dags att jag skaffade en egen, vilket jag inte Continue reading Modifiering av 2-m-saxen ROX-2X
There is a newer version of this antenna in the following post: Improved 2 m Fox Hunting Antenna . This article describes a Yagi antenna I have designed for use in a fox hunting receiver for the 2 m band (144 MHz). The antenna uses 25 mm wide steel tape measure for the elements, 16 mm Continue reading 2 m Fox Hunting Antenna
Det här blogginlägget är andra och avslutande delen i en artikelserie där jag beskriver en mottagare (“rävsax”) för radiopejlorientering på 80m-bandet. En snarlik variant av artikeln publicerades i Sveriges Sändaramatörers, SSA:s, tidskrift QTC i nummer 10 och 11, 2022. Denna andra del beskriver elektroniken, mekaniken och mjukvaran. Blockschema Figur 16 visar ett blockschema över mottagaren.…
Det här blogginlägget är första delen i en artikelserie där jag beskriver en mottagare ( rävsax ) för radiopejlorientering på 80m-bandet. En snarlik variant av artikeln publicerades i Sveriges Sändaramatörers, SSA:s, tidskrift QTC med början i nummer 10, 2022. Denna första del beskriver bakgrunden till projektet, hur radiovågor, antenner och pejling fungerar på 80m-bandet samt hur jag Continue…
Anyone who has tried to take a photo through the ocular of a microscope knows that it can be very hard to get the camera correctly positioned. The slightest deviation from the ideal position results in a less than full field of view. There are five degrees of freedom to get right, X, Y, Z, Continue reading Microscope adapter for mobile phone camera