Ham Engineering vs SpectraHold

Ham Engineering is the engineering bench for amateur radio — antenna and feedline maths, circuit design, propagation and a deep reference library, all completely offline. No account, no ads, no tracking, and not a single network call. ANTENNAS • Half-wave dipole with adjustable k (velocity) factor, quarter-wave and 5/8-wave verticals, ground-plane radials, end-fed half-wave, random wire, full-wave loop and a 3-element Yagi estimator • Matching: L-network, Pi-network, quarter-wave transformer, balun/unun ratios and stub matching • Antenna Lab — a live elevation radiation-pattern plot with directivity, realized gain, takeoff angle, beamwidth, front-to-back, mismatch loss, feedline loss and system gain, each explained • Grid Compass that rotates with your phone, showing beam bearing and distance from your grid to a target grid • Antenna gallery — every common type drawn as scalable vector art, with what it is, what it is for and what to watch out for FEEDLINES & RF • Coax loss by cable type, frequency and run length; velocity-factor electrical length • SWR from forward/reflected power, plus return loss and mismatch loss • Antenna A/B comparison and receiver noise-floor estimation • RF power conversions: dBm, watts, ERP and EIRP • Propagation: free-space path loss, radio horizon and Fresnel-zone clearance • NanoVNA and tinySA quick-start guides, and a coax + connector gallery CIRCUITS • Ohm's law, series/parallel resistance, voltage dividers, RC and RL time constants • Reactance, LC resonance, Q and bandwidth, stored energy • RC and LC filter cutoffs, a constant-k Pi/T filter designer, a bandpass/notch calculator and a Butterworth low-pass designer • Resistor, capacitor and inductor code decoders, an AWG wire table and a 555 timer calculator • A live RLC resonance lab and a 50-part component gallery REFERENCE & EXTRA • Filterable amateur band plan for ITU Regions 1, 2 and 3 • Unit converters including watts, dBm and microvolts • Comparison tables for coax, connectors, antennas and batteries • Tools-and-gear and rig-controls galleries — what every knob and button is called across manufacturers • Maidenhead grid tools and great-circle beam headings • 300+ searchable tips, 40+ formulas, a rich glossary and a constants reference • Curated external links to major retailers, brands and references BUILT FOR THE BENCH • Nearly 200 illustrations drawn as scalable vector art — nothing to download, everything sharp at any size • Works fully offline. The app makes no network calls at all • Export any panel or diagram as a theme-aware image to share or file • An (i) explanation on every panel — this is a tool and a guide, not a quiz • Light and dark themes, adjustable font size, weekly tips and in-app version history • Your callsign, grid and email stay on your device and are never transmitted PERFECT FOR • Licensed operators designing, building and tuning antennas • Anyone putting up a first dipole or vertical and wanting the numbers right • Homebrewers and kit builders working with filters, matching and components • SWLs and newcomers who want the reference material without the exam drill • Club elmers and anyone teaching antenna and RF fundamentals PRIVACY • Your callsign, grid and email are stored only on your device. • No account, no sign-up, no ads, no analytics SDKs, no advertising ID and no tracking of any kind. 73 de A41UX Yousuf AL Balushi — Unixeer, Oman

The spectrogram with memory. SpectraHold turns microphone input into a 3D spectrogram. Watch frequencies in real time, freeze the view, and explore up to 120 seconds of visual history to inspect a detail you just heard. FREEZE AND EXPLORE Tap the graph to inspect a frequency. Zoom and browse the history, then return to live analysis whenever you want. ADJUST THE VIEW Choose a visible window from 1 to 20 seconds, color palettes, and automatic or manual visual gain from −40 to +40 dB. Visual gain changes the graph without changing microphone gain. FEATURES • Real-time 3D spectrogram from 20 Hz to 20 kHz. • Adjustable history from 20 to 120 seconds. • Frequency inspection, zoom, and history navigation. • Up to two estimated peaks per region: bass, midrange, and treble. Detection does not confirm resonance. • Background capture and capture with the screen locked, while permitted by the system. • Compatible with iPhone and iPad. Audio is processed on your device. History stays in memory; no audio file is saved or uploaded. Closing the app or a system interruption may stop capture. TRIAL AND PURCHASE Download for free. Activate a free 7-day trial to access all features. After the trial, analysis stops until you purchase full access. The unlock is a one-time purchase, with no subscription or automatic charge. The local price is shown before you confirm the purchase. You can restore purchases. SpectraHold is a visual analysis tool. It does not apply equalization, automatically eliminate feedback, or replace a calibrated sound pressure level meter. Estimates depend on the microphone, device, and recording conditions.