security alarm circuit

Antentop: Loop Antennas - Article on radiation patterns of small loops, equivalent circuits of loop antenna, small loops as receiving antennas, ferrite loops

Building Coaxial Traps - This page describes the design and construction materials W8WWV used to build a coaxial cable trap. A coaxial cable trap is a parallel resonant circuit that is usually inserted in an antenna element to enable multiband operation.

Multi Band Antenna Traps - These devices are called Traps, but they are actually more like frequency sensitive switches. They are parallel resonant, high Q, tuned circuits which provide a very high impedance at their frequency of resonance.

Getting the most from your tuner - Here is how to adjust this popular tuner circuit so it transfers maximum power to your antenna without going snap

A remote antenna tuner - Interesting project to remotely control, using a servo control circuit, a common commercial antenna tuner by N30X

Fun With Tubes - A noncommercial site operated by Max Robinson and dedicated to passing on and preserving knowledge of vacuum tube circuits and techniques.

Antique Radio Schematics and Capacitors for Tube Radios - Specializes in antique radio schematics and capacitors. carries antique radio schematic diagrams and electronic circuit service information for american, canadian and european antique radios.

Canadian Antique Radios Schematics Diagrams Service - We specialize in canadian antique radio schematics for vintage tube radios made in canada. we carry lots of factory electronic circuit schematic diagrams as well as all rcc / radio college of canada service data 1920's - 70's.

Boston-Area University Police Radio - Police and Security Broadcasts at Harvard University, Boston-Area University Police Radio. Cambridge; Boston.

Bucks & Montgomery Live police scanner - Live Police/fire/ems scanner link for Southeastern PA area including Bucks, Montgomery Counties and Philadelphia plus South Jersey area

E. H. Armstrong - Radio's premier inventor, Edwin H. Armstrong was responsible for the Regenerative Circuit (1912), the Superheterodyne Circuit (1918), the Superregenerative Circuit (1922) and the complete FM System (1933).

Citizen Weather Observer Program - A private-public partnership with three main goals to collect weather data contributed by citizens; to make these data available for weather services and homeland security; and to provide feedback to the data contributors so that they have the tools to check and improve their data quality

ARDF transmitter for 80 meters - The 80m TX described here is the well known ON7YD ATX-80 and timer, combined and re-engineered to fit a readily available enclosure by G3ZOI

Polaris USA - Radio programmin equipment, radio programming cables, all sort of cables and connectors, webcams, cameras, security products

ExpressPCB - Free PCB software is a snap to learn and use. For the first time, designing circuit boards is simple for the beginner and efficient for the professional.

Spot - Intelligent DXCluster Client - Reliable amateur radio software for OS X and Windows that works the way you expect. Spot allows you to chase the DX that really matters by putting you in charge of which DX spots you need to see and alarming you when they appear.

HamTimer - HamTimer was written by WF0GM to provide a way of showing both UTC Time and Local Time simultaneously, Provide a reminder to the Amateur Operator to identify his/her station every 10 minutes as necessary, Sound an alarm for WWV solar activity announcements each hour.

AM-6154 FAA Amplifier circuit conversion - AM-6154 222MHz grid Conversion Information by N0UK

Rotator Brake Delay and Protection Circuit - A rotator modification by W4ZT

A simple VOX circuit - Here is a 3 transistors 6 diodes circuit that is a Voice Operated Tx PTT control as well as an ANTI VOX circuit to stop mis-operation from Rx noise by G8MNY

NiCad battery charger - A basic nicad battery charger using a single medium power transistor.

Homebrew FT 817 Headset - A simple circuit to homebrew your own headset for the Yaesu FT-817

A Power Supply on the Cheap - Need a variable power supply that is short circuit protected and over voltage protected; Here is a good one that can be built cheap by VE3IVJ

External Keypad for FT-817 - An external keypad for FT-817(ND), for the serious portable/field-day contester/operator. Homebrew it with the free firmware and public circuit diagram. The circuit is very simple and takes power supply from the ACC port of the radio

A regenerative receiver with 6SN7GT - Circuit to build a regenerative receiver