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Index

• General information
• Amateur radio
• Antennas
• Broadcasting
• Receivers
• Transmitters
• Other radio related circuits
• Microwave communications
• Radio Data System (RDS)
• Regulations
• Radio frequency interference
• Other unsorted links

General information

• AC6V's Amateur Radio and DX Reference Guide
• Counterintelligence and Counterterrorism WWW Page - information about surveillance and counter surveillance
• Doug Lung's R.F. Technology Page - Focusing on TV RF Broadcast Technology
• Harris Broadcast Communications Technical/White Papers
• Mobile commucation and cellular phone link
• Radio Components & Interference
• Radiohistoriaa, Kyynel, Sever, sodanaikaisia sotilasradioita - radio history, text in Finnish
• RF Design articles online
• RF Energy Safety - Reprint from QST and the ARRL Handbook
• RF Integrated Circuits - list of some commonly used types
• Signals and Measurements for Wireless Communications Testing
• The quest for the ideal rf amplifier
• The RC Transmission! - text explains what kind of signals are sent from the TX to the RX of an "FM" radio control set, how they are decoded, and ideas about producing it yourself
• The Smith Chart - an RF engineering aid by Phillip Smith of RCA many years ago
• Why my radio bought from USA does not work well in Europe ?

Frequency allocation

• Allocation of Radio Spectrum in the United States - a list showing how the radio frequency spectrum is allocated to different users in the United States
• Frequency Allocation Tables in USA
• Some shortwave stations which can be listened in Finland - text in Finnish

Amateur radio

• An amateur radio design tutorial
• ARRLWeb - the American Radio Relay League's home on the World Wide Web!
• AX.25 Amateur Packet-Radio Link-Layer Protocol
• Baycom Modem - A BAYCOM Packet Radio modem is the cheapest way to get on the air, here is the circuit diagram of it
• eHam.net - Amateur Radio Community Site
• Electronic projects and radio design links for the amateur radio and electronics hobby enthusiasts
• Electronic projects by Roberto Barrios - radio programming cable for Kenwood TM-V7 and TM-G707, programming cable for Yaesu FT50, VX1 and VX5 , Luxman I Bus Interface, radio interface box for the Motorola Radius GP300
• Finnish Made PMR, Trunking and Cellular (NMT) Phone Amateur Radio Conversion Pages - modification examples for Nokia, Mobira, Televa, Benefon etc.
• G3SEK's Amateur Radio Technical Notebook - practical HAM information and tips
• Grounding Systems for Amateur Radio Stations - you need good grounding for both safety and good operation of radio equipments
• GW4OFQ's Home Page - amateur radio links
• Hamquest - an internet auction site created solely for the ham community
• Ham Radio Online - articles and projects
• ICOM Microphone Notes - how to interface other than original microphones and headsets to it
• Ilpo J. Leppäsen sivut DX-kuuntelijoille - pages for DX-listeners in Finnish
• Introduction to Packet Radio
• KB0UDF's Mod's And Stuff
• Linux HAM HOWTO
• Manic Hand Builder - Pure amateur hand builders webpage for HAM. Designing PCB mask pattern by MS-paint, make own UV-sensitive thin-filmed PCB from junk PCB. Build DDS VFO controled by PIC16F84. Build ARDF receiver, using PLL LO, controlled with PIC.
• Meteor & Colorgramme - Radioastronomy Meteor scatter detection software, uses a small electronic interface
• Mini-Circuits Application Notes - collection of RF component and circuit related application notes
• Monitor Internet Amateur Radio Links
• Morse Code Beacon Keyer
• Morse Code Practice Oscillator
• Online Radio & Electronics Cource - free on-line course orgnaized by Austrailian Amateur Radio Club
• Packet Radio Linkpage
• PD0HNI's World wide Link Page - Over 600 direct links to radioamateur sits,shops,manufacturers and dealers.
• PSK31 & SSTV Interface Home Page - radio interfacing details
• Radio abbreviations
• Radio stuff - useful HAM related documents
• Radio-TNC Wiring Diagrams
• Soundcard to radio interface
• SSTV - Slow Scan Television - articles and web links
• Suomen Radioamatööriliitto ry - The Finnish Amateur Radio League - SRAL
• Sääsatelliittiharrastajan käsikirja - weather satellite reception handlbook in Finnish
• TAPR - an international organization dedicated to amateur digital communications
• The Morse code
• The phonetic alphabet
• The Q code
• TNC to Transceiver Interface Diagrams - Packet Radio's most complete TNC to Radio diagrams, and illustrations on the worldwide internet. These pages are intended to support the Packet Radio users and the AX.25 digital Amateur Radio Operator. The page describes how to interface to various radios.
• Track and Solve Electrical Interference
• Understanding Power Splitters - how they work, what parameters are critical, and how to select the best value for your application
• Understanding Soundcard Interfacing - how to connect soundcard to HAM radios
• VK2TIP Ian Purdie's radio design tutorial pages - for amateur, ham radio, electronic project enthusiasts as well as the electronic hobbyist
• Yet Another 9k6 Modem - multi-standard modem for packet radio using FPGA chip

RF components information

• How RF Transformers Work
• Introduction to Directional Couplers
• Introduction to modulators - information on RF modulators
• Measuring the electrical performance characteristics of RF/IF and microwave signal processing components
• Mini-Circuits Application Notes
• Most Often Asked Questions About Electronic Attenuators
• Most Often Asked Questions About QPSK Modulators
• Most Often Asked Question About RF Limiters
• Most Often Asked Questions About Power Splitter / Combiners
• Understanding Mixers - general information on RF mixers and how to measure mixer performance
• Understanding Power Splitters
• Understanding VCO Concepts

Antennas

Antennas are passive devices that radiate and pick up radio frequency energy (RF). Antennas do not create RF energy. In transmitting applications antennas focus the energy in a pecific area or direction, which increases the signal strength in that direction or area. This is specified as Gain in units of dBi. An antenna with 0dBi gain is one which radiates in all directions equally. An antenna with 12dBi gain, has a direction in which the signal is 12db stronger than in another direction. In reception the antenna gain helps to the antenna to pick up signals from one direction stronger than from other directions. This directivity is very important if you need to receive weak signals in noisy environment.

General

• A new look at the Ufer ground system - Mr. Ufer developed the concept of concrete encased grounding electrodes which are suitable for radio antennas
• Antenna Info - basics of antenas and most commonly used antenna types
• Antenna information - information on dipole and GP transmitting antennas
• Antenna Options - Survey of Antenna Characteristics and Types - antennas mainly for TV transmitters
• Antennas - some basic information and resource links
• Antennas: critical links in the wireless signal chain - right antennas can strengthen the chain by yielding better signal coverage, increased S/N ratio, reduced bit error rate, and lower power consumption all at very low cost
• Basics of Dual-Polarized Antennas Tutorial - information on special antennas used in celluar networks
• Exploring the secrets of the Smith chart* - an indispensable tool
• FM Antenna Configuration vs Performance
• Good ground, great signals - how to do geounding of antennas well
• Grounding Tips - how to ground antenna systems
• HAM antenna documents and programs
• How to Use a Smith Chart - The Smith chart appeared in 1939 (Ref. 1) as a graph-based method of simplifying the complex math (that is, calculations involving variables of the form x + jy) needed to describe the characteristics of microwave components. Although calculators and computers can now make short work of the problems the Smith chart was designed to solve, the Smith chart, like other graphical calculation aids (Ref. 2), remains a valuable tool.
• Install your antenna properly
• Jim's Notebook - all sorts of interesting and useful antenna data, techniques, hints and such
• Near field or far field? - How do we define the far field of an antenna system, and what criteria define the boundary between it and the near field? The answer depends on your perspective and your design's tolerances.
• Pasternack Connector Identifier - pictures to help to identify different coaxial cable connector types and impedances
• Radiation impedances of wire and rod antennas
• Smart Antenna Systems Tutorial - A smart antenna system combines multiple antenna elements with a signal-processing capability to optimize its radiation and/or reception pattern automatically in response to the signal environment
• The Bunny Ears - the traditional indoor antenna: problems and design flaws
• Up On The Roooof - tips for installing FM and TV antennas to roof

Antenna cabling issues

• 50 ohms versus 75 ohms in antenna cable
• Most Often Asked Questions About Power Splitter / Combiners
• Putting a Balun and a Tuner Together - information on antenna baluns and their use
• Quarter-Wave Power Divider - use this to phase two antennas together for increased gain
• RF BALUNs - one of the most important components in of transmitting system is the antenna feeder system
• Signal Cabling - quite often the humble feed line is to blame if the communication does not work
• The purpose of a balun - information on benefits of balusn in eadio reception
• Transmission Line Transformers - theory, articles and construction details for RF transmission line transformers

Antenna building projects

• 2304 Tech List - Many radio atenna building project documents on-line. Pages have also many radio equipment plans on-line.
• A J-Pole antenna for the Ramsey FM10a in GIF format - transmitting antenna tuned for 89 MHz
• Antenna extension provides open-door policy - garage door opener receiving antenna for 315 MHz
• Balloon or kite antenna? Why not
• Build a Yaki-Uda Antenna - instructions for building and designing 3 and 6 element yagi antennas
• Build a UHF Discone Antenna
• Construction Details For A GPS Helix Antenna - antenna for 1.5 GHz band for GPS receiver
• DIY GPS Antenna - antenna for 1.5 GHz band for GPS receiver
• Down To Earth Antennas - reception antennas which work close to earth
• Experiments on Remote Receiving Loops
• FM Dipole for 88-108 MHz
• Go ATV Portable With This Simple Beam Antenna! - a simple broadband yagi for 70-cm band
• How to build a Corner Reflector Antenna - for UHF reception and transmission
• How To Make A Simple Ground Plane Antenna - A ground plane antenna is a very simple antenna. It is a quarter wave vertical radiator and four radials that simulate a ground for the radiator. It directly matches to 50 ohm coax and should show a VSWR of 1.5:1 or better at its center frequency. It is useful from HF through UHF, although it tends to be large below 30 MHz.
• Hybrid quad reflector array with approx. 6 dBd gain
• Long Loopstick Antenna - to improve AM radio reception without using a long wire or ground
• Practical indoor antennas for everybody - HF foil antennas, VHF/UHF discones, wire beams, VHF/UHF rotables, tape antennas and telescoping VHF/UHF indoor beams
• Satellite Antennas Hints and Kinks: Low Cost Satellite Antennas
• Simple dipole antenna for 88-108 MHz FM Reception

Active antennas

• AM/FM/SW active antenna - an active antenna that can be used for AM, FM, and shortwave, on the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna
• AM/FM/SW active antenna
• Q - Multiplying Loop Antenna - active antenna for 500 kHz to 1750 kHz frequency range

Antenna amplifiers

• 50 Hz - 100 MHz Wide-Band Preamp - ampifier 17..37 dB, uses general purpose transistors
• TV antenna amplifier - covers the frequencies from 40 to 900 MHz, suitable frequency rage for FM or TV antenna amplifier
• Medium Wave Preamp - The tuning voltage is variable from 1 to 12 volts and is designed to cover the medium waveband from about 550Khz to 1650Khz

Antenna baluns

• 4:1 balun for 160 to 10 meters
• 75 ohm to 300 ohm balun
• A Cost Effective Current-mode 1:1 Balun - can be constructed from a length of coax and a rod typically used for a broadcast antenna loop-stick, some electrical tape, cable ties, a length of PVC water-pipe and some connectors
• Baluns and coaxial aerials - many examples on blauns built from coaxial cable
'

Impedance matching

• Impedanssin muunto neljännesaaltomuuntimella - how to change impedance with quarter wave microstrip adapter, text in Finnish

Antenna filters

• ATV rejection filter for R/C applications - This filter is a 0.1 dB Tschebychev lowpass with a rejection of 90 dB or better at 430 MHz, and 0.2 dB insertion loss at 72 MHz. The 3 dB cutoff frequency is 120 MHz.
• Build a VHF Notch Filter!
• Coaxial Stub Filters: A range of easy-to-build RFI filters by John Regnault, G4SWX
• Simple high-pass filter to cut off disturbing signals
• Wideband filter uses image parameters - You can design various lowpass and highpass filters using image parameters

Signal attenuators

• Attenuator Pads - homebrew attenuation pads

Antenna related measuring equipments

• Antenna Analyzer 88-960 MHz
• Field Strength Meter - measures radio field strength at VHF frequencies in the range 80 - 110 MHz
• LED driver displays standing-wave ratio
• Simple Field Strength Meter - simple and also quite sensitive, uses an ordinary digital voltmeter to measure signal strength, works on VHF and FM bands
• Simple Analog Field Strength Meter - can be used from 30 MHz to over 2 GHz

Other antenna related circuits

• 6 Meter Heliax Duplexers
• A simple anti-static device - circuit to help to reduce static buildup in antenna
• Bias Tee - Bias tees allow you to insert DC voltages into your signal path (coax) without disrupting the existing signal in that path, for example for feeding active antennas
• Modify that AM antenna - add external antenna connector to your AM radio which does not have it

Broadcasting

• Automate NPR=s All Things Considered with the Pause Detector
• Homebrew Broadcasting book: Pirate Radio and TV Broadcasting Techniques - full book text on-line
• Low Power Broadcasting FAQ
• MrBroadcast.Com - broadcasting links
• Radio airs a digital future - broadcast radio lags television in the conversion to digital transmission
• Radio Data System (RDS) Forum
• The Free Radio Network
• The Official Pirate Radio Kit Bulletin Board
• The Pirate Radio Emporium - transmitter circuits, information
• VHF Pirate Radio Electronics Introduction - modulation, stereo, pre-emphais, compressors, limiters, transmitters and amplifiers described

Radio Data System (RDS)

A system to add text information to FM radio broadcasts which RDS radios can receive.

• 68HC11 based RDS decoder
• La Réalisation D'un Décodeur RDS - RDS decoder circuit, text in French, but you can use automatic translation to English

Digital Audio Boradcast (DAB)

• COFDM the best asset for DAB-T
• Digital Audio Broadcast (DAB) Technical Papers

Receivers

• 40-Metre Direct Conversion Receiver - can be used for receiving amateur radio QSO signals in CW as well as in SSB mode in the 40-metre band
• 4 Band Double-Tuned Preselector - covers MW and Sw to 30MHz
• Aircraft Receiver - A passive receiver for listening to the pilot, pdf file
• Build your own superheterodyne receiver - simple three-IC superheterodyne radio to receive stations in the 4.5- to 10-MHz range
• Classic detector enables low-cost receiver - super-regenerative receiver's sensitivity is better than 1 mV, and it operates over a wide range of VHF
• Crystal Radio - very simple circuit
• Doppler D/F Instruments - a doppler type VHF radio direction finder for HAMs and experimenters
• Crystal Radio Set System Design, Measurement and Improvement - This site contains articles on design, measurement and improvement of crystal radio sets
• Electronic Eaverhopping Device Detector - detects transmitters in 1-1000 Mhz range
• FM Band Preamplifier - This low noise amplifier will bring in those low-power stations
• FM crystal receiver with slope demodulation construction project - passive FM receiver for 87-108 MHz
• FM Radio Spectrum Analyzer - a device which will display the strength of all FM Radio stations simultaneously
• FM SCA--Subsidiary Communications Authorization or FM Subcarrier Information - An Educational Document
• How to build a DCF77 receiver for PC
• Old Time Crystal Radio - plans of one electronics kit
• One Transistor FM Radio Project - description of low-cost FM-receiver kit
• Op Amp Radio - very simple AM radio
• Poor Man's Spectrum Analyzer - information about an electronics kit
• A Simple-To-Build Superhet Receiver - a simple circuit for a superhet radio receiver that can be built up in sections, with each section tested before assembly, can be tuned to different bands
• Single chip builds tiny aircraft receiver - simpel AM receiver for 108 to 135 MHz using single-chip NE605
• Spectrum analyser kid - simple spectrum analyzer for frequencies between 0 and 33 MHz
• Stereo Decoder - for FM receiver
• The R2 Single Sideband Direct Conversion Receiver, Revisited: The R2a
• $10 receiver has microvolt sensitivity - three-transistor circuit receives signals in the 5- to 15-MHz short-wave band and operated from 9V battery

Transmitters

Remeber that radio transmitters need a permit to have and operate at the give frequency. In some countries (USA) you are allowed to do very small power broadcasts if you do not cause interference and stay within the FCC limits. In other countries it might be illegal to have this type of radio transmitter with you (exceptions are circuits for measurement purposes which are packed in metal boxes and do not have antenna so can't be used for illegal broadcasting). Remeber that if you operate a radio transmitter without a permit you can get quite high fines or go to jail in many countries. Even owning a radio transmitter without a permit is illegal in many countries. Check the local legistlation before starting to build or use any radio transmitter. You should check the law before buying any transmitting equipment as a fine, confiscation of equipment and/ or imprisonment can result from illegal use or ownership. The laws vary from country to country, and overseas readers should therefore check local laws.

General information

• CB-Radio Component Database
• Estimating Transmitter Distance - simplified equation for analysing low power radio transmitters, for line of sight
• Hum Reduction in FM Stereo Transmitters - It is convienient and easy to use a wall transformer with FM stereo or AM transmitters, but often unwanted hum appears on the transmitted signal. This problem can be sometimes frustrating and difficult to correct.
• To Design and Build a Portable, Miniaturised, Multichannel FM Transmitter
• UHF Construction Precautions - If you are building a kit or circuit that operates at VHF (over 30 MHz) or UHF (over 300 MHz) you should be made aware of proper wiring and construction practices. This is largely experience combined with a good theoretical understanding.

FM transmitters and related circuits

• 15W FM-transmitter - 15-18W FM-transmitter (88-110Mhz) that is powered from 14-18 Volts/2,5-3,5 A power supply
• 2 Transistor FM Voice Transmitter - can be tuned to operate over the range 87-108MHz
• 3W FM Transmitter - operates between 90 and 110 MHz
• 4 Transistor Transmitter - provides an FM modulated signal with an output power of around 500mW at around 100 MHz
• 4 Watt FM Transmitter - This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation. This circuit has an output power of 4 Watts and works off 12-18 VDC.
• Basic FM Transmitter
• FM Band Monaural Transmitter - Varactor diode gives high quality modulation, pdf file
• FM Broadcast VCO and Buffer - for 88-108 MHz
• FM Band Monoaural Transmitter - high quality monoaural FM transmitter, FET based oscillator
• FM Stereo Transmiter
• FM Transmitter - low powered FM transmitter, includer circuit board and parts placement picture
• High Fidelity FM stereo matrix generator circuit - circuit is for use with mono transmitters to give out clear stereo output
• Long-range FM Transmitter - power output of 200-250 milliwatts and range up to about 2 kilometres, frequency around 100 MHz
• Low Power FM Transmitter- oprates from 9V battery, frequency range aroun 90-108 MHz, can take microphone or line level signals in
• Micro Power FM Broadcasting Circuits - accessories to transmitter circuits: audio limiter, audio mixer, antenna and essential modifications for Ramsey FM10
• Mighty's Pirate Radio - many radio circuits, including mono and stereo FM transmitters
• Phone Broadcaster - telephone call FM transmitter
• Simple FM Band Transmitter - very simple crystal controlled transmitter for 70-110 MHz FM band, no modulation option provided
• Simple FM transmitter - circuit is a simple two transistor (2N2222) FM transmitter powered by a 9 volt battery
• Small Radio Transmitter - information about building a small radio transmitter, which has a PCB 1.75" x 2.5" (45mm x 68 mm) and has a range of about 30 yards or so at 85-108 MHz frequency range
• Small Radio Transmitter
• Um excelente gerador de FM para a faixa de 88 a 108 MHz - PLL syntetized generator of FM for the band of 88 the 108 MHz, text in portugese, you can use automatic translation to English
• We-man's radio circuits - FM transmitters, fax interface and antenna design

FM wireless mics

• FM Room Bug - circuit diagram description and PCB layout
• FM Transmitter Kits for Beginners
• High power FM mic
• Resonant Frequency of a Colpitts Oscillator - gives formulas how to analyze the operation of the example 96.8 MHz wireless microphone circuit
• Small Radio Transmitter - information about building a small radio transmitter, which has a PCB 1.75" x 2.5" (45mm x 68 mm) and has a range of about 30 yards or so at 85-108 MHz frequency range

Ramsey FM10 transmitter kit related circuits

Ramsey FM10 is a popular FM transmitter kit based on BA1404 IC. The kit is sold by Ramsey. The accessories designed for FM10 are useful for other radi projects also.

• Ramsey FM-10 Info - modifications, output amplifier, RF probe, filters, antenna
• Ramsey FM-10 Five Essential Modifications

Telephone transmitters

• FM Telephone Bug
• FM Telephone Transmitter
• Phone-bug - A simple transmitter that is powered from the phoneline
• Simple wireless FM bug

RF transmitter amplifiers

• The 500W Radio Power Amplifier - for 160, 80 and 40 meter bands

Radio remote controlling

• Ensemble domestique HF 4 voies - 4 channel radio remote controller which controls 4 relays, text in French, try automatic transtation to English
• Four-way remote control uses series transmission - four channel remote controller system which uses 433 MHz band

Other radio transmitters

• 136kHz and 73kHz circuits
• 1.5 Volt Tracking Transmitter -fFrequency range is the usual 87-109Mhz on the FM dial
• 900Mhz 9600bps Radio Link - reference design from the AVNET electronics page for a wireless 9600bps transceiver
• AM radio tone transmitter using 4049 hex inverter - produces an audible whine at 1000 kHz on your AM dial, crystal controlled frequency
• A Single Triode 350 Watt Power Amplifier With the Svetlana 572B - for frequencies below 30 MHz
• FM Oscillator - circuit for a VCO and buffer that operates across the entire FM broadcast band (88-108 MHz)
• Micropower AM band radio station - simple transmitter offers surprisingly good signal quality, pdf file
• Micro Power AM Broadcast Transmitter - 74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a class C amplifier configuration
• N5FC's 2N2222 40 Meter CW/DSB Transceiver
• Op amp based AM radio transmitter - operates at 1 MHz and takes sound from microphone
• Powerless transmitter
• Radio circuits by Kazuhiro Sunamura - over 100 simple radio circuits
• Simple 2-meter transmitter
• SSB Modulator - generates SSB signals from 35MHz to 80MHz
• UKW Sender - operates from one 1.5V battery, lacks some coil information

Other radio related circuits

Radio equipment interfacing

• Connect two standard office telefax machines via 2 meter ham radio (at 2400 bps) - zipped file
• Telephone line to radio patch

Radio modems

• Baycom Modem - A BAYCOM Packet Radio modem is the cheapest way to get on the air, here is the circuit diagram of it
• Packet Radio Modem Schematics
• Yet Another 9k6 Modem - multi-standard modem for packet radio using FPGA chip

Amplifiers

• High-frequency AGC has digital control - 50 mHz AGC circuit
• High-frequency VGA has digital control - variable-gain amplifier for ranging from 115 MHz at high gain to 225 MHz at low gain
• Laajakaistaiset vahvistimet - information on building broadband amplifiers in Finnish
• Transistor PA Bias Circuits - information how to bias transistors on RF power amplifiers
• Wideband AGC has 60-dB dynamic input range - provides more than 60 dB of dynamic input range at 150 MHz

Modulators

• 602 Double Balanced Mixer - Philips describe their 602 mixer (SA602A) circuit as "a low-power VHF monolithic double-balanced mixer with input amplifier, on-board oscillator, and voltage regulator. It is intended for high performance, low power communication systems. The guaranteed parameters of the SA602A make this device particularly well suited for cellular radio applications.
• Add-on modulator has high bandwidth - converts the output of a continuous-wave (CW) source to either an amplitude-modulation (AM) or a suppressed-carrier-modulation (SCM) format, circuit has unity gain and 50 Ohm input and output impedances, frequency response is flat from 0.3 to 45 MHz
• Current amp provides frequency modulation - you can use current-feedback op amps in many VHF-band RF applications up to 150 MHz, this frequency modulator that generates a 55-MHz VHF signal
• SSB Modulator Draws Only 5mA At 2.7V - SSB modulator circuit
• Modulator draws just 5 mA at 2.7V - single-sideband (SSB) modulation uses the frequency spectrum and generates output power more efficiently than does full-amplitude modulatio, generates generates 35- to 80-MHz SSB signals by combining wideband, low-voltage op amps with an IC that integrates all the necessary functions
• Single-sideband demodulator covers the HF band

Demodulators

• 10.7MHz FM DETECTOR - FMIF-DET is based upon a SN7401 quad NAND gate with open collector outputs
• Waveform generator demodulates FM signals - uses the phase-detector signals of a precision waveform-generator IC to perform FM demodulation

Converters

• 900-MHz down converter consumes little power - nonproprietary 900-MHz down converter to 75 MHz by using an 825-MHz local-oscillator signal

Oscillators

• Low-cost circuit biases VCOs for cable and TV - PLLs are useful in a variety of applications, most notably cable and TV tuners
• Op-amp oscillators simplify RF designs - a novel circuit that uses a low-cost, high-speed op amp as a crystal-controlled RF sine-wave oscillator

Radio signal detectors

• Cellular Phone Helper - activates a variety of devices when your cellular phone is in use, pdf file
• RF Sniffer 500 kHz to 500 MHz

Filters

• Analysis of pairs of Coax Stubs - article about coaxial stubs for filters on transmitters
• Analysis of Single Coax Stub
• K2TR Coax Stub Filters
• W3LPL Receiving Bandpass Filters - information extracted from a July/August 1985 NCJ article

Remote control

• Radio Remote Control - uses VG40T and VG40R VHF remote control modules

Other

• Audio mixer for Ramsey FM10 transmitter: schematic and description
• Harry's Homebrew Homepage - very many radio related projects
• Micro Power FM Broadcasting Circuits - limiter, mixer, antenna, modifications to Ramsey FM10
• Radio and RF circuit at Wenzel Associates technical library

Microwave communications

• An Experimental 10-Mbit/s Microwave Data Link - this link operates at 10GHz band
• Inexpensive Multi-Megabaud Microwave Data Link - this link operates at 10GHz band

Regulations

Radio frequency interference

Interference is any unwanted signal which precludes reception of the best possible signal from the source that you want to receive. Interference may prevent reception altogether, may cause only a temporary loss of the desired signal, or may affect the quality of the sound or picture produced by your equipment. Interference to home electronic equipment is a frustrating problem; but, fortunately, there are several ways to deal with it.

• Colin's Interference Handbook - Interference to home electronic equipment is a frustrating problem; but, fortunately, there are several ways to deal with it. This handbook provides a step-by-step process for eliminating the interference
• Computer EMI
• Dealing with Computer generated RFI/EMI
• Electromagnetic Interference in Hearing Aid T-Coil Applications
• EMI from RF-Driven Lamps
• General Information about EMI/RFI
• How to avoid radio interference to audio equipment and telephone - written in Finnish
• QST October 1992 Lab Notes on Telephone EMI - amateur radio telephone interference
• Radio Components & Interference
• Radio Frequency Interference (RFI) Information Page
• Radio Interference Primer for R/C Flyers
• Radio Interference Problems for R/C Flyers
• Radio Frequency Interference To/From Touch Lamps and Dimmers
• The ARRL Technical Information Service - lots of documents on radio interference
• Using ferrites for interference suppression

Other unsorted links

• FM-only radios - Very complete radio collector's site of FM only radios. Site include historical information, theory, photographs, and a few unique projects.
• MEIsearch - mobile electronic industry search
• The Wireless Set No. 19 website - The Wireless Set No. 19 website celebrated this vintage military WW II "tank" radio, now collected, restored and carefully used by some Amateurs all over the world. This site includes technical information, operating procedures (from war-time manuals), photos, first-hand experiences, weekly and monthly on-air nets and much, much more.

© 2001, 2002 Advantage Computers, Inc. – Brian Palmersheim (KB0ETC) All Rights Reserved.