Science & Nature
1439 sites
Subcategories:
- Astronomy & Space (396)
- Chemistry (8)
- Earth Sciences (26)
- Biology (79)
- Physics (30)
- Mathematics (59)
- Weather & Climate (104)
- Amateur Radio (682)
- Electronics (47)
https://antenna.it/
Giovannini Elettromeccanica is an Italian antenna manufacturing company specializing in HF antenna systems for both military and commercial applications, covering the RF spectrum from 1.5 to 30 MHz. Their product catalog includes log-periodic antennas, broadband wire dipoles, fiberglass masts, antenna rotators, and towers, with research, design, manufacturing, and support services all offered in-house.
http://blackcatsystems.com/
Black Cat Systems offers a wide catalog of Windows and macOS software focused on ham radio, shortwave listening, and audio utilities, including tools for SSTV decoding, ACARS, ALE, propagation forecasting, and Morse code training. The site serves as both a software storefront and a hub for amateur radio enthusiasts, with free trials available for most programs.
https://arpgalaxy.com/
A comprehensive amateur astronomy resource dedicated to Halton C. Arp's Atlas of Peculiar Galaxies, cataloging all 338 peculiar and interacting galaxy entries with supporting data, imagery, and observing guidance. Built by and for amateur observers, the site bridges professional archival photography from the Palomar 200-inch telescope with modern amateur CCD imaging to show that anyone with a backyard telescope can observe these remarkable objects.
http://radiowrench.com/sonic/index.html
A long-running free resource archive started in 1997 offering downloadable manuals, service documents, and technical diagrams for VHF/UHF radios, repeaters, antennas, and related RF equipment. The site hosts PDFs covering everything from GE MVP repeater manuals to tone decoder boards and duplexer specs, making it a valuable reference for amateur radio operators and radio technicians.
http://jap.hu/electronic/rf.html
Peter's RF schematics page is a technical reference collection of radio frequency circuit diagrams spanning receivers, transmitters, and transceivers across a wide range of frequencies from 27MHz to 1GHz. Hobbyists and engineers will find schematics for superregenerative receivers, FM audio transmitters, walkie-talkies, SAW-based designs, and datasheets for chips from major manufacturers like Silicon Labs, HopeRF, and Texas Instruments.
https://asteroidoccultation.com/
Steve Preston's long-running resource provides predictions for asteroid occultation events, listing when asteroids will pass in front of stars as seen from Earth. Covering upcoming events through 2026 with supplementary observation guides and FAQs, it serves as a reference for amateur and professional astronomers tracking these brief but scientifically valuable phenomena.
https://marsradio.org/
Branson Repeaters serves the Missouri Ozarks Tri-Lakes area with a network of linked ham radio repeaters on 2 meters, 1.25 meters, and 70 cm, plus digital nodes connecting YSF, DMR Brandmeister, AllStarLink, and EchoLink. The site provides repeater frequencies, coverage details, hosted net schedules including a Skywarn Youth net, and local Branson weather from NOAA.
http://jap.hu/electronic
Peter's DIY electronics hub showcases a range of original hardware projects including relay modules for Raspberry Pi and Arduino, PIC microcontroller circuits, remote control encoders, and an LCD thermometer. Each project comes with schematics and build guides, making this a great resource for hobbyist engineers looking for practical, hands-on circuit designs.
http://charlieselectronics.com/
Charlie's Electronics is the home base of AB5U, a Dallas-area ham radio operator running multiple UHF and VHF repeaters across the Dallas-Rowlett-Garland region. The site covers amateur radio topics, two-way radio repair services, off-grid power and cooling for field operations, and practical electronics tips.
http://collembola.org/
A comprehensive scientific checklist of all Collembola (springtails) species in the world, searchable by taxon and linked to global distribution maps at family, genus, and species levels. The site also includes biology overviews, identification guides, collecting techniques, bibliographies, and images, making it an invaluable reference for entomologists and naturalists.