The Analog Edge is a 14-part field guide to the half of a scanner that software can’t fix: everything between the antenna and the ADC. The issue tracker keeps teaching the same lesson — half the hard bugs were in the samples, not in the code — and this series turns those postmortems into working knowledge: what dBFS actually measures, how to stage gain without chasing a software threshold, what clipping, intermod and phase noise each look like from the decoder’s side, which sample rate to run, and how antennas, feedline, filters and LNAs decide your noise floor before GopherTrunk sees a single sample.

It is the operator’s companion to two concurrent series: where Weak-Signal Engineering explains the algorithms that recover a marginal signal, The Analog Edge is about not being marginal in the first place — and about capturing honest evidence (pre-combine IQ, sidecar metadata) when you are. One thread runs the length of the series: a system that decodes cleanly on a hardware scanner but garbles in software, and the analog-side causes eliminated one part at a time.

Every post reads three ways: a TL;DR + cheat-sheet for skimmers, bold headers, tables, and diagrams for the medium read, and full prose with real measurements for the deep read.

New here? Start with What hardware do I need? for the shopping list, then come back for how to make it sing.<ol class="post-list series-list"><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 1: Where the Software Ends</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">The signal chain from antenna to ADC and why no code change can fix a problem on the analog side of it — an inventory of GopherTrunk issue-tracker bugs that turned out to live in the samples, and the map of a 14-part field guide to the front end.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 2: dBFS — What the Number Means (& What It Doesn’t)</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">A precise definition of dBFS for SDR operators — full scale, peak versus RMS, the readings GopherTrunk exports, and why two captures peaking at the same −48 dBFS can differ by 10 dB of usable signal, which makes dBFS a headroom meter and never a quality meter.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 3: Gain Staging — Never Chase a Software Threshold</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">How to set SDR front-end gain the measured way — the operator who raised gain 17 dB to clear a software constant by 0.2 dB, the ladder method scored by decode quality, autogain’s lock-then-error-rate-then-lower-gain tie-break, and the tenths-of-a-dB config trap.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 4: Clipping, Overload & Intermod</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">What front-end overload actually looks like from the samples up — rail-pinned IQ, the clip ratio as the authoritative verdict, intermodulation products that manufacture phantom signals as gain rises, out-of-band overload from FM broadcast, and why a clean clip ratio still doesn’t clear the front end.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 5: Phase Noise & Reciprocal Mixing — The Ten-Megasamples Lesson</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">The front-end failure no level meter can see: how oscillator phase noise smears modulation while leaving the carrier looking clean, retold for operators through the #764 verdict — same antenna, same signal, 10 dB of demod SNR gone at one sample rate and not the other.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 6: Sample Rate — The Decode Path Doesn’t Care; the Front End Does</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">Why GopherTrunk’s decoders are deliberately rate-invariant — every capture rate is normalized to one per-protocol channel rate before the receiver ever runs — so a symptom that tracks the sample rate indicts the capture, plus what higher rates genuinely buy and the two warnings that mean the consumer fell behind.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 7: Antennas for Trunking Bands</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">Antenna craft for trunked-radio monitoring — which bands the systems actually live in, why antenna gain is a radiation shape rather than free signal, polarization, when height beats gain, and how to choose between a discone, a tuned vertical, and a yagi for a fixed system.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 8: Feedline & Connectors — Where dB Go to Die</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">Why the coax between your antenna and your SDR quietly costs more decode margin than any software setting — published loss figures per cable class at 800 MHz, the real price of every adapter, and why receive-side loss is worse than the half-your-power framing suggests.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 9: Filters & LNAs — Adding Gain Without Adding Garbage</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">When a low-noise amplifier actually helps, why its position in the chain matters more than its gain figure, how bandpass and FM-notch filters buy back headroom on a hot band, and the decision rules for ordering filter, LNA, and coax so you don’t amplify your own problems.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 10: Capture Discipline — cfile, cs16, SigMF & Metadata</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">Why “get the raw capture” is the most repeated sentence in the GopherTrunk issue tracker, the IQ formats and sidecar metadata that make a capture usable, the tap points that decide what a recording can prove, and how a good capture turns a complaint into a regression test.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 11: Two Antennas — Diversity & MRC From the Operator’s Seat</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">What a second antenna and maximal-ratio combining actually buy on a fading trunking band, how to configure GopherTrunk’s diversity mode and read its health log line, and the coherence signature that tells you when two antennas cannot be combined with one wideband gain.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 12: Front-End Classes — Shared LO vs Independent PLLs</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">Why two receive channels on one chip keep a constant relative phase while two daughterboards with their own synthesizers lock at a random phase and walk afterwards, how that hardware class decides between mrc and mrc-static, and how the branch_phase_deg log field identifies your class without recording anything.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 13: Coherence, Not dBFS — Scale-Invariant Health</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">The story of an operator who raised front-end gain seventeen decibels to push a number past a software constant, and the scale-invariant cross-correlation that replaced the gate — why coherence answers the question a calibrator actually asks, and why DC removal inside it is load-bearing.</p></li><li class="post-card"> <h2 class="post-card__title">The Analog Edge, Part 14: The Field Checklist — Is It RF or Is It Software?</h2> <p class="post-card__meta"> Tutorials </p><p class="post-card__desc">The whole series folded into one triage flow — dBFS, clipping, gain sweep, rate A/B, capture, coherence — a decision tree for splitting radio problems from software problems, the order to spend hardware money in, and the send-off for the marginal system that started it all.</p></li></ol><p class="blog-feed-link"> See all tutorials or subscribe via RSS. </p>