QR Previewer vs Ham Engineering

**QR Previewer** helps you check a QR destination before you open it. Instead of launching a website immediately, QR Previewer shows where the QR code leads first, so you can decide what to do next. **Features** * Preview the destination before opening * View a readable URL and domain details * Review local risk signals such as HTTP links, short links, IP-based hosts, and heavy tracking parameters * Get a cleaner link suggestion when removable tracking parameters are detected * Choose how to continue: open in Safari, use the in-app browser, or copy the link * Revisit your most recent scans on this device **Why use QR Previewer** QR menus, event links, and shared codes often open too quickly. QR Previewer adds a simple review step, making it easier to inspect unfamiliar destinations before visiting them. **Important** QR Previewer provides local heuristic guidance only. It does not guarantee safety and is not a malware scanner or phishing blocker. **Privacy** Scan results are processed on device in the current version. QR Previewer itself does not upload your scanned URLs or scan history.

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