Amateur radio training · work in progress

Bench Test

Interactive pages for the technical part of the amateur radio syllabus. The circuits are solved in the browser as you change them.

Each page turns the circuits from a syllabus group into working instruments. There are controls for the component values. Move one and the page solves the circuit again: the readings update, the waveforms redraw, the working underneath substitutes the new values, and the charge moving round the schematic changes speed to match the current in each branch.

Everything on the page is calculated as you move the control, from a nodal analysis of the circuit. The pages are free, run entirely in the browser, and work offline once loaded.

They are meant to sit alongside a course and the books, for the reader who wants to see a circuit respond before the idea settles.

The pages

Group 2H

Tuned circuits

Resonance, Q, bandwidth, dynamic resistance and the four filter shapes, with the circulating current visible in the tank.

Foundation, Intermediate, Full

Group 2I

Semiconductors

Diodes, Zeners, varicaps, transistor characteristics and biasing, the three configurations, amplifier classes and oscillators.

Intermediate, Full

Group 2F

Sampling

Converters, quantisation, sample rate and aliasing, from what a converter does at Foundation to Nyquist and noise at Full.

Foundation, Intermediate, Full

Each page covers every level that teaches the group. The level buttons at the top switch the whole page, so the same instruments appear with the depth, the equations and the worked answers set for that level.

Checks

These run every time the pages are built, and a page that fails one is not written out.

What is checked	Result
Assertions on the nodal analysis, signal processing and DC maths	73 pass
Every circuit joined up, with every lead landing on something	12 layouts
Every wire and component carrying a current the circuit solves for	12 layouts
Kirchhoff at every node, swept across the control range	0.000000%
Content: level coverage, working shown with numbers, terms defined before use, answers sourced	14 checks
Every page at every level, loaded and read back	9 of 9

Reading the finished picture. The displays are checked from the rendered image as well as from the maths. Each trace is located by its colour and the two are compared down the page, so the check proves that a phase inversion is visible on screen and that both traces are drawn at a size you can see.

That check was added after the common emitter amplifier calculated its phase inversion correctly, drew it correctly, and showed both traces on one vertical scale, which put a ten millivolt input and a two volt output on the same axis.

Still to come

The remaining syllabus groups. Three of the technical groups are built, and the per level item lists for the rest are ready.
One schematic on the oscillator page. The panel works and the figures are right; the tuned circuit and its feedback tap are described in the text and will be drawn.
Questions at Foundation and Intermediate, once the RSGB publishes those banks. Full level questions are in place with worked answers.
Audio, once the visual side is settled.

Feedback

Any reaction is welcome, and these in particular:

Is the pitch right at each level, and does switching level change enough to be worth having?
Does showing the working with the numbers substituted help, or is the formula on its own enough?
Does the moving charge in the schematic teach anything?
Anything technically wrong, which is the most useful of all.

It is free, it will stay free, and it is not commercial in any form.