A standalone, hands-on track that runs alongside the syllabus rather than inside it:
physical electronics from the ground up, laddering into RF and SDR. Every rung is build → measure → understand,
and reinforces theory you meet elsewhere in the syllabus. Progress and purchases save in your browser, seeded from
the committed data/bench.json; export to publish it on GitHub.
Rungs completed0 / 8
Equipment acquired£0 / £0
The ladder · low-level → RF → SDR
Climb in order — each rung assumes the gear and the intuition from the one below. The
“reinforces” links jump to the syllabus subject that rung makes physical.
0
Bench & DC fundamentals
Build Voltage dividers, LED current-limiting, potentiometer control, Wheatstone bridge
Measure I–V of a resistor, continuity and voltage with the DMM, source resistance
Reinforces Foundation — the substrate for everything above
Projects
Ohm's law & tolerance — drive known resistors at 5 V, predict then measure the current; grab 10 of one value and log the spread. Target: readings within meter tolerance; spread inside the rated ±5%.
Voltage divider under load — 10k/10k reads 2.5 V open, then sags when you hang a 10k load on the tap. Target: loaded output matches the Thévenin prediction (1.67 V).
Diode / LED I–V — plot a few Vf/If points, find the ~1.8–2 V knee, then size a series R for exactly 10 mA. Target: your chosen R lands within a mA of 10.
1
AC, reactance & the oscilloscope
Build RC / RL / RLC passive filters, diode rectifier + smoothing capacitor → a DC supply
Measure Corner frequency, phase shift vs frequency, LC resonance and its Q
RC low-pass — R 1.6k, C 100 nF → fc ≈ 1 kHz; sweep the function gen 100 Hz–100 kHz and find the corner. Target: −3 dB point within 10% of 1 kHz, −20 dB/decade slope, −45° phase at fc.
RLC resonance — series RLC; find f₀ = 1/(2π√LC), measure Q from the −3 dB bandwidth, vary R from under- to over-damped. Target: f₀ within 10%; Q roughly the R-predicted value.
Rectifier + smoothing — full-wave rectify, add a cap, measure ripple vs load. Target: ripple within ~20% of I/(f·C).
Common-emitter amp (2N3904, Av ≈ −10) — measure mid-band gain, the −3 dB bandwidth, and watch it clip when overdriven. Target: gain within 20% of −Rc/Re; you can point to both roll-offs.
Op-amp gain–bandwidth (TL072) — build ×1, ×10, ×100 and measure the bandwidth of each. Target: gain × bandwidth ≈ constant (~3 MHz).
Sallen-Key vs passive RC — same fc, second-order active filter. Target: a visibly steeper −40 dB/decade skirt, plus any peaking near fc.
Schmitt trigger — measure the two switching thresholds (the hysteresis window) and clean up a noisy ramp. Target: a stable output on an input that makes a plain comparator chatter.
3
Oscillators — RF is born
Build Colpitts / Hartley LC oscillator, crystal oscillator; wind your own toroidal inductors
Measure Frequency and its drift/stability, measured inductance, a first faint carrier on a nearby AM radio
Wind your own toroid — N turns on a T37-6; compute L = AL·N² and measure it on the NanoVNA. Target: measured L within ~10% of the AL·N² prediction.
Colpitts LC oscillator (~7 MHz) — measure frequency, then the drift over a 10-minute warm-up, and how a trimmer pulls it.
Crystal oscillator — same circuit, crystal instead of the LC tank. Target (the payoff): drift of a few ppm vs the LC's hundreds — stability you can watch appear.
VNA calibration + Smith chart — SOL-calibrate, then measure a known 50 Ω load. Target: S11 lands at chart centre, return loss > 30 dB.
L-network match — match a 200 Ω load to 50 Ω at a chosen frequency with an L and C. Target: return loss > 20 dB at the design frequency; watch it walk to centre.
Homebrew diode-ring mixer — 4× matched 1N4148 + two trifilar toroids; measure the sum/difference products and conversion loss, compare to an SA612. Target: ~6–8 dB conversion loss.
Crystal ladder filter — select a matched set from your batch, build a 4-crystal ladder, sweep S21 on the NanoVNA. Target: a clean bandpass ~2–3 kHz wide with measurable insertion loss and shape.
Dipole + SWR — build a half-wave dipole, sweep SWR, trim to resonance. Target: SWR < 1.5 at the target band.
5
Analog receivers
Build Crystal radio → amplified AM envelope detector → a direct-conversion (Tayloe) receiver for a ham band
Measure Sensitivity, demodulated audio, image rejection; hear a real signal you built the whole chain for
Crystal radio — 1N34A envelope detector + LC tuned circuit + high-Z earpiece. Target: receive a local MW station with zero power.
+ LM386 audio — add the amp to drive a speaker; note the sensitivity jump.
Direct-conversion RX — SA612 mixer + crystal/VFO local oscillator + audio amp, on 40 m. Target: actually copy SSB/CW audio through a chain you built end-to-end.
6
SDR & digital communications
Build Decode ADS-B / NOAA APT / AIS; capture GPS L1 and correlate against the C/A codes; a GNU Radio QPSK link (HackRF TX → attenuators → RTL-SDR RX)
Measure BER vs Eb/N₀ against theory, the constellation, spectral occupancy via FFT
Decode ADS-B (1090 MHz, dump1090) — your first real capture: live aircraft on a map.
NOAA APT (137 MHz) — decode a weather-satellite image on a pass (an antenna + timing challenge).
GPS L1 acquisition — capture raw IQ at 1575.42 MHz and correlate against the C/A Gold codes in Python/GNU Radio. Target: a clear correlation peak (code phase + Doppler) for ≥1 satellite.
QPSK link + BER curve — Pluto TX → attenuators → RTL-SDR RX; sweep attenuation and plot BER vs Eb/N₀ over the theoretical Q-function. Target: measured BER tracks theory within 1–2 dB; a clean constellation.
7
Capstone — tie it all together
Build A software GPS receiver (acquire → track → pseudorange → position fix) or a QPSK modem link with forward-error-correction over the two-radio bench
Measure End-to-end link performance; a real position fix from raw IQ you captured
A · Software GPS receiver — extend rung 6: acquisition → DLL/PLL tracking → nav-message decode → pseudoranges → least-squares fix. Target: a position fix within tens of metres from your own captured IQ.
B · QPSK modem with FEC — add framing, sync, and convolutional coding + Viterbi to the rung-6 link. Target: demonstrate the coding-gain shift in the BER curve and transfer a file error-free.
Shopping list · ~£1,145 build (Amazon.co.uk, inc VAT)
All sourced from Amazon.co.uk (UK stock, inc VAT) — genuine parts, no clones. Buy in phases as you climb; the
“equipment acquired” meter tracks spend. Prices are current 2026 GBP and drift — check the linked page.
Tip: the RX-only core (everything except the Pluto) is ~£920 and covers rungs 0–6 — add the Pluto when
you reach the transmit work to keep initial spend lower.
Phase 1 · Benchunlocks rungs 0–2~£340
Soldering iron — Pinecil V2 + tips + USB-C PD supplygenuine PINE64 (SNN002); needs a USB-C PD brick (or DC5525 supply) to run£55Amazon.co.uk →
Solder — 60/40 leaded, 0.7 mm (100–250 g)leaded melts easiest for hand work; lead-free is an option. The fumes are rosin flux, not lead£10Amazon.co.uk →
Fume extractor — fan + activated-carbon filterpulls rosin-flux smoke away from your face; the Loops bench unit ships with spare filters£25Amazon.co.uk →
Digital multimeter — UNI-T UT139Ctrue-RMS, auto-range, 6000-count, temp/cap/freq — ample for the bench (the UT61E+ is a £139 overkill)£35Amazon.co.uk →
Toroid cores + enamel wireT37-6 / FT37-43 — Amazon has only mixed 3rd-party packs; SOTABEAMS (UK) is the reliable alt£18Amazon.co.uk →
First upgrades, when you want them (not counted above): TinySA Ultra spectrum analyzer (~£110 —
with the Pluto you lose HackRF's hackrf_sweep, so this is the handiest add) · a two-channel bench
function generator · a better dummy load / RF power meter. On HackRF: the original HackRF One is now
discontinued and mostly out of stock in the UK (a “HackRF Pro” is incoming), which is the practical reason the
Pluto is the recommended TX radio here.
Component kit · itemised
What the “component assortment” line should actually contain to carry you through rungs 0–5.
Buy assortment kits where sensible (resistors, ceramics) and specific part numbers where they matter (RF diodes,
JFETs, mixer ICs). Click any part for a note on what it is and why it's here. The Amazon mega-kit above
covers most passives and jelly-bean semis; the specific RF parts (crystals, JFETs, mixer ICs, toroids) are
hit-or-miss on Amazon, so QRP Labs,
Rapid and
CPC are the reliable specialists.
Passives
¼ W resistor kit, E12 10 Ω–1 MΩ~600 pc
The workhorse. E12 is the standard 12-values-per-decade ladder for 5% parts. Prefer metal-film over carbon for lower noise — you'll notice it in the receiver front end. Through-hole ¼ W is fine into low VHF; higher up, lead inductance starts to bite.
50 Ω is the universal RF system impedance; the E24 range has no exact 50, so 51 Ω is the stand-in (or two 100 Ω in parallel). A single ¼ W 51 Ω makes a usable low-power dummy load to ~VHF; parasitic inductance limits it at UHF.
Multiturn trim pots 1k / 10k / 100k5 each
Set-and-forget internal adjustments — bias points, oscillator amplitude, calibration. Multiturn (25-turn) gives fine, stable resolution vs a single-turn trimmer.
Panel potentiometer 10 kΩ linear×3
A user-facing knob: receiver volume, a VCO tuning voltage, output level. Linear taper, not logarithmic/audio taper.
Ceramic cap kit, 1 pF–100 nF (incl. C0G/NP0)assortment
Dielectric class is everything. C0G/NP0 (Class I) is low-loss and rock-stable → use in oscillator tanks and filters. X7R/X5R (Class II) packs more capacitance but its value slides with voltage and temperature → bypass/decoupling only. An X7R in a tuned circuit will drift on you.
Film caps 1 nF–1 µFaudio / filters
Non-polarised and low-distortion — the right choice for audio-band filters (Sallen-Key) and coupling. Polypropylene is the lowest-distortion type.
Electrolytics 1–1000 µFassortment
Bulk capacitance for supply smoothing (rung 1 rectifier) and audio coupling. Polarised (reverse them and they pop), have real ESR, and age — never in an RF path.
Trimmer caps 5–30 pFosc tuning · ×5
Small variable capacitors to net an oscillator exactly onto frequency or fine-tune a matching network.
Silver-mica / C0G 10–470 pFRF resonators
The high-Q, ultra-stable RF capacitor. Silver-mica is the classic (superb stability, bulky, pricey); C0G ceramic is the modern equal. For filters and tanks where Q and drift are what count.
Inductor assortment 0.1–1000 µHfilters
For quick LC breadboarding and DC chokes. For real RF you'll wind your own on the toroids — higher Q and a known value — rather than trust a molded choke.
Semiconductors — discrete
2N3904 NPN / 2N3906 PNP×25 each
The canonical small-signal BJTs — a complementary NPN/PNP pair, ~200 MHz fT. The “hello world” of transistor circuits (rung 2 common-emitter amp).
2N2222A general-purpose NPN×20
A beefier classic NPN (~800 mA, ~300 MHz fT) for switching and small-signal where the 3904 runs short on current.
BC547 / BC557×20 each
The European NPN/PNP equivalents of the 3904/3906 — same roles, and what most UK kits and literature use.
2N7000 N-MOSFET×10
A logic-level N-channel MOSFET: voltage-controlled with very high input impedance — genuinely different physics from a BJT, and a clean switch / level-shifter to feel the contrast.
J310 / MPF102 JFETRF amps/osc · ×10
Low-noise, high-impedance JFETs that shine at RF — receiver front ends and Colpitts oscillators. They're depletion-mode (conducting at Vgs = 0), which shapes the bias design. Buy the J310; wild MPF102s are often relabelled fakes.
2N3866 / MPSH10 RF transistor×5
For when the 3904 runs out of frequency. 2N3866 is a small ~½ W RF power device (TX driver/buffer, good to a few hundred MHz); MPSH10 is a cheap VHF/UHF small-signal NPN (fT ~650 MHz). Here fT and layout matter more than DC gain.
1N4148 signal diodemixers · ×50
The ubiquitous fast switching diode — detectors, clamps, switching. Buy 50 so you can select matched quads for a hand-built diode-ring mixer (rung 4).
1N4007 rectifier×20
1 A / 1000 V mains rectifier for the rung-1 power supply. Rugged and cheap, but slow — not for RF or fast switching.
1N34A / BAT85 SchottkyAM detector, ring mixer · ×10
Low forward drop (~0.2–0.3 V). The germanium 1N34A is the classic crystal-radio AM envelope detector — its low turn-on recovers audio from a weak RF envelope; the BAT85 silicon-Schottky is the modern equal, also good in ring mixers.
Zener assortment 3V3–12 V · LEDsassortment
Zeners clamp to a set reverse-breakdown voltage — references, regulation, protection. LEDs are indicators (and rough ~1.8 V references).
ICs
TL072 dual op-amp×5
JFET-input dual op-amp: low noise, high input impedance — the default for active filters and buffers (rung 2). Not rail-to-rail; wants a couple of volts of headroom.
LM358 / NE5532×5 each
A deliberate contrast. LM358 is cheap and single-supply-friendly (works near the negative rail) but noisy — fine for DC/sensor/control. NE5532 is the low-noise audio-grade part for the receiver's audio chain. The lesson: there's no universal “best” op-amp.
LM393 comparator×5
A comparator, not an op-amp: built to switch fast, with an open-collector output that needs a pull-up. Turns an analog threshold into a clean digital edge — Schmitt trigger, squaring an oscillator, zero-cross detect.
NE555 timer×5
The legendary astable/monostable RC timer: clocks, PWM, test tones, and a hands-on lesson in RC timing. Not precise or quiet, but endlessly useful.
78L05 / 7805 / LM317 regulatorsassortment
Linear regulators for clean, quiet DC rails — fixed 5 V at 100 mA / 1 A, and the resistor-set adjustable LM317. Linear means low noise but heat to dissipate; that quietness helps oscillators and receivers.
Mixers, and worth having both kinds. The NE602/SA612 is a Gilbert-cell active mixer-plus-oscillator “receiver on a chip” (tiny parts count, little LO drive). The ADE-1/SBL-1 are Mini-Circuits passive diode-ring modules — higher dynamic range but needing a strong LO. Your known-good reference to compare a hand-built ring mixer against.
LM386 audio ampreceiver audio · ×3
The tiny audio power amp that drives a small speaker or headphones — the standard final stage of a homebrew receiver (rung 5). Build the RF and detector, then the LM386 makes it audible.
RF, oscillator & construction
Crystals: 3.579, 4.9152, 7.68, 10, 14.318 MHzseveral each
A quartz crystal is a mechanically-resonant sliver of quartz that behaves electrically as a very-high-Q series RLC (the “motional” Lₘ/Cₘ/Rₘ) shunted by electrode capacitance C₀. Its Q of 10k–100k+ is far beyond any LC tank, which is why a crystal oscillator holds frequency to ppm while an LC one drifts. It has two close resonances — series fs (low-Z) and parallel fp a few kHz above — and the gap between them is its “pullability” (how far a trimmer can drag it). The listed values are all cheap, mass-produced ones: 3.579545 MHz is the NTSC colour-burst crystal (the near-free hobbyist staple), 14.318 is 4× that (old ISA-bus part), 4.9152 a UART baud crystal.
Matched 10 MHz crystalsladder filter · ×8
A crystal ladder filter — the narrow ~2–3 kHz IF bandpass at the heart of a superhet — is several near-identical crystals, each contributing a pole. They must match within tens of hertz or the passband smears and ripples, so you buy a batch, measure each (on the NanoVNA, or a test oscillator + frequency counter), and select a matched set. Hence over-buying eight.
Ferrite beads / RF chokesassortment
A ferrite bead is a frequency-dependent resistor that soaks up RF (decoupling, killing parasitic oscillation, EMI). An RF choke feeds DC bias into an RF stage while blocking the signal from escaping. Small parts, but they keep RF where you put it.
SMA PCB/edge connectors + pigtails×5
SMA is the 50 Ω coax standard your NanoVNA, Pluto and attenuators all speak; these attach your homebrew boards to that world.
BNC connectors×2
The bayonet connector on your scope and function generator (the sub-GHz instrument side); bridges bench gear to the circuit.
A blank PCB used as a ground plane for “Manhattan” (glued pads over a solid ground) or “dead-bug” (ICs upside-down, leads in air) RF construction. Breadboards are hopeless above a few MHz — stray L and C everywhere — so a solid ground and short leads are non-negotiable at RF. The build style is itself a rung-3/4 skill.
Perfboard / stripboardassortment
For making lower-frequency (audio, DC, control) builds semi-permanent once they work. Stripboard has copper strips; perfboard is plain holes. Not for RF.
Solid-core 22 AWG is the correct gauge for breadboards — it fits the springs and holds its shape; multi-colour keeps you sane. Use stranded only for flexible off-board leads.
DC barrel jacks + 9 V battery clipspower
Power input. The battery clip isn't just convenience — running a sensitive receiver from a battery removes mains hum and supply noise, making rung-5 measurements much cleaner.
Working notes
Solder safely
The smoke off the iron is vaporised rosin flux, not lead — it irritates the airways, so run the
fume extractor and work in a ventilated spot. The lead risk is ingestion, not fumes: don't eat or drink at
the bench and wash your hands afterwards. Wear safety glasses (flicked solder and clipped leads), and rest the
hot iron on its stand over the silicone mat.
The loopback BER bench
For the digital-comms rungs, loop transmit into receive over coax through attenuators — either the
Pluto in full duplex (TX and RX on one box) or Pluto TX → RTL-SDR RX. Dial the attenuators to sweep BER
against Eb/N₀. No antenna radiates, so it's legal and it's a cleaner measurement than any over-the-air link.
Transmit legally: loopback first
Radiating on ham bands generally needs a licence (US Technician / UK Foundation). Keep all TX work on a
dummy load + attenuators over cable — no antenna radiating — which needs no licence and is better for measurement anyway.
A licence later just unlocks going on-air.
Seeing spectrum
The Pluto has no built-in wideband sweep, so cover spectrum with the RTL-SDR (to ~1.7 GHz), the NanoVNA,
and the scope's FFT; a TinySA Ultra (~£110) is the first upgrade for a proper spectrum analyzer. (A genuine HackRF
would give you hackrf_sweep to 6 GHz for free, but it's discontinued and scarce in the UK — see the note above.)
Homebrew depth
Wind your own toroids and build the L-match and diode-ring mixer by hand in rungs 3–4 — that's where the
RF intuition lives — but keep a jelly-bean mixer IC (ADE-1 / SBL-1) on the shelf as a known-good reference to compare against.