Electromagnetic radiation is a wave that combines electric and
magnetic fields, moving out from its source as an expanding sphere and having waves as the
feilds alternate in value. This kind of radiation has different properties as its
wavelength changes. We call this radio waves.
Waves of a very long wavelength, such as thousands of meters, tend
to travel along the surface of the earth and even penetrate into the water. These are
useful for communication with submarines. Radio, television, cellular telephones,
walky-talkies, 2-way police radios, and other such communication/broadcast systems use
electromagnetic radiation, or "Radio Frequency Waves". Each communication
service uses a part of the spectrum that is suitable for its needs.
A radio wave used to transmit audio signals is a complex signal that
contains the carrier frequency of the broadcast station and the audio signal to transmit
(usually from the microphone or audio amplifier source). The function of the radio
receiver is to recover the audio signal that was modulated onto the RF carrier at the
radio station, and apply it to the speaker, reproducing the sounds of the announcer. There
are various ways to combine the carrier frequency and the audio signal together. This
process is called modulation. The most commonly used modulation methods are amplitude
modulation (AM), frequency modulation (FM), single sideband modulation (SSB) and phase
modulation (PM). Also digital signals can be modulated to radio frequency carrier.
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
Walkie-talkies provide a cost-effective alternative for cellular
phone use in business or family conmmunications at short distance. WIth a set of small and
robust walkie-talkie radios, its easy for your group to remain in contact. Simply press
the Push-to-Talk button to instantly speak to your group.
General information
Directive
1999/5/EC - Directive of 9 March 1999 of the European Parliament and of the Council on
Radio Equipment and Telecommunications Terminal Equipment and the mutual recognition of
their conformity (1999-04-07 OJ No L 91/10).
Handheld
Radio Equipment Page - This page attempts to keep track of the array of low power
systems available to the public (excluding telephones) such as CB, FRS, GMRS, MURS, SRBR
etc.
Personal Radio Services -
Services issued in USA by FCC. This is official FCC page on those services.
R&TTE Ditective
- As of 2000 april 8th within the European Economic Area (EEA) Radio and
Telecommunications Terminal Equipment (R&TTE) is brought under the CE Marking scheme.
So far a type approval was required for equipment like telephones, mobiles e.g. DECT, GSM
and DCS1800, transmitters like remote controls and the like. Now, like most other
equipment, the type approval is replaced by a self certification scheme in accordance to
the R&TTE Directive (99/5/EC).
CTCSS?
DCS? Sub-channels? - With "tone squelch" the radio receiver can be set to
only open its squelch if this tone is received. Any interference would not have the
correct tone present, and so the radio would remain quiet. Continuous Tone Coded Squelch
System was developed into a system with numerous standard tones to choose from, often 37.
Some manufacturers call these "sub-channels". DCS is similar to CTCSS in
practice, but uses a digital code instead of continuous analogue tones.
CB is one of the Citizens Band Radio Services. It is a two-way voice
communication service for use in your personal and business activities. Expect a
communication range of one to five miles. 27MHz CB was the first system that the public
were free to use for business purposes, with a license of course, and that anyone else
with a CB could legally listen in. Nowadays in USA license documents are neither needed or
issued, when you use an unmodified FCC certificated CB unit.
CB Radio Net Ring - This
is a web ring dedicated to CB Radio Communications.
PMR446 stands for Personal Mobile Radio. PMR446 was introduced in
spring 1999 to supersede some other short range radio systems. PMR446 is Europe-wide
licence free standard for hand-portable two-way radios, anyone, individual or business,
can make use of affordable and useful walkie-talkie radios. PMR 446 is a Europe-wide
standard for radios that can be bought and used by anybody for business or leisure
purposes. This means that in most European Union countries PMR 446 walkie talkie radios
can be used with no special permission or license needed. PMR446 standard allows for
license-free legal use of same walkie-talkies throughout the European Union.
PMR446 walkie-talkie radios are simple to operate, have 8 channels
on UHF frequencies (around 446 MHz, 12.5 kHz channel spacing) at transmission power of
500mW max, and work at ranges of up to two or three kilometers. PMR446 radios use FM
modulation (F3E) for audio. PMR446 radios have 0.5W ERP transmitting power and a fixed
antenna on equipment (no external antenna allowed). PMR446 radios recommended (but not
obligatory) to use CTCSS selective squelch system (sometimes called sub-channels). Most
radios use CTCSS system with up to 38 channels (the number of supported tones and tone
numbering can vary from manufacturer to manufacturer). PMR446 related specifications are
ETS 300 296 (RF) and ETS 300 297 (EMC).
PMR446 walkie-talkie radios are made by a variety of companies,
including Motorola, Maxon, Kenwood, Goodmans, Icom, Maycom, Multicom, Cobra, Yeasu,
Panasonic and others. Radios for use on this service are less expensive than conventional
licenced equipment. The very cheapest are suitable for leisure use whilst the more
expensive are ideal for professional business applications. In most European countries you
do not need a license, or pay any type of "user fees" or subscriptions. You
simply purchase a radio, and batteries, and then you may immediately use the radio. Most
PMR446 sets use either normal AA size cells, or the smaller (half the weight) AAA cells.
When using this type of radios please note that PMR446 is not a
cellular system or secure communications channel. All transmissions may be listened to by
other PMR446 users, or those people with scanners. Please also note that PMR446 radios are
only allowed to be used for voice communications.
http://www.fcs.org.uk/mrc/final-29jan01.htm
- PMR into the Future is a joint initiative from the Federation of Communications Services
and the Radiocommunications Agency in response to the changing and challenging environment
for the PMR community.
The
"naughty stuff" page... - PMR446 is ideal for UHF radio experiments, without
needing an amateur radio license. This page has technical information on PMR446 radio
system. This pages has also information on PMR446 antennas.
Family Radio Service (FRS) is a very low power short range two-way
radio service in the 460 MHz band in use in USA. FRS was created specifically for the use
of families and small groups. This service allows the group to use a small, easy to use,
and relatively inexpensive two-way radio for the purposes of voice communication between
members of the group. FRS standard license-free radios are for sale to the general public.
The Family Radio Service is a service developed for use by the
general public at large. This service is not intended as a "hobby" service; and
currently, usage reports indicate this is a typical trend. Users of FRS typically wish
only to communicate with others of their own group. You do not need a license, or pay any
type of "user fees" or subscriptions. You simply purchase a radio, and
batteries, and then you may immediately use the radio.
Family Radio Service walkie-talkies have 14 channels, use UHF
frequencies and have a legally-limited transmission power of 500mW. FRS radios are legal
to use only in the USA.
Notes: You may ONLY use FRS radios in the United States and Canada!
All FRS units are compatible with one another in basic operation. Radios with CTCSS tones
all use essentially the same tones. These tones are just in a different order. Many
manufacturers advertise "privacy codes" on their radios. Wording "privacy
code" is misleading, because all transmissions may be listened to by other FRS users
(in channel monitor mode), or those people with scanners.
Family
Radio Service (FRS) Information - This page was created to assist the general internet
public in finding information about the U.S. Family Radio Service. (FRS)
Use of analogue trunked radio systems began back in the mid 80's. In
trunked radio system every radio on the system 'listens' on a control channel, that is a
data transmission giving the radios all their instructions. When a call is received, or
made, the controlling data transmission tells the radios who wish to speak to each other
which channel they need to switch to. When speaking on their voice channel a normal
'talktrough' repeater is used to allow the sets to talk to each.
This system allows efficient use of radio channels. A system of 12
repeaters and controller could support several hundred if not a thousand or more customers
(not all of them need to be allocated their own frequencies). Simply put, trunking permits
a large number of users to share a relatively small number of communication paths - or
trunks. Commercial telephone communication is a wireline version of trunking.
Equipment is available from many manufacturers as MPT 1343/1352 is a
open standard. The analogue trunking system band is spilt into two parts, so that
receiving and transmitting has differnt frequencies (usually 8 MHz difference).
TETRA is digital mobile radio technology that has been accepted
throughout Europe. It is a standard defined by ETSI (European Telecommunications Standards
Institute), and brings new features to mobile communications. It combines the features of
mobile cellular telephones with fast data communications and the workgroup capabilities of
PAMR and PMR. This system offers small handsets, up to 28.8kbit/s data rates, almost
instantaneous call set up times, "press to talk" (PTT) capability, broadcast
facilities and hand over between cells. TETRA uses TDMA (Time Divisional Multiple Access)
technology at 410 - 430 MHz frequency range. TETRA offers fast call set-up time,
addressing the critical needs of many user segments, excellent group communication
support, Direct mode operation between radios, packet data and circuit data transfer
services, frequency economy and excellent security features. TETRA uses Time Division
Multiple Access (TDMA) technology with 4 user channels on one radio carrier and 25 kHz
spacing between carriers. This makes it inherently efficient in the way that it uses the
frequency spectrum. TETRA trunking facility provides a pooling of all radio channels which
are then allocated on demand to individual users, in both voice and data modes.
The new all digital civil Tetra (Trans European Trunked Radio)
system operates in the band 410-415 MHz Portable Transmit and 420-425 MHz Base Transmit
(it might be expanded in the future). For civil systems in Europe the frequency bands
410-430 MHz, 870-876 MHz / 915-921 MHz, 450-470 MHz, 385-390 MHz / 395-399,9 MHz, have
been allocated for TETRA by the ERC Decision (96)04.
For emergency systems in Europe the frequency bands 380-383 MHz and
390-393 MHz have been allocated for use by a single harmonized digital land mobile systems
by the ERC Decision (96)01. Additionally, whole or appropriate parts of the bands 383-395
MHz and 393-395 MHz can be utilized should the bandwidth be required.
TETRA MoU - TErrestrial
Trunked RAdio (TETRA) is an open digital standard defined by the European
Telecommunications Standards Institute (ETSI). The TETRA Memorandum of Understanding (MoU)
represents 85 organisations from 29 countries working with TETRA.
Amateur radio is a friendly, high-tech hobby that's got something
fun for everyone! When you pass an exam, you an become an Amateur Radio operator--no
matter what age, gender or physical ability. People from all walks of life pass their
entry-level exam and earn their Amateur (ham) Radio license. They all share the diverse
world of activities you can explore with ham radio. The rules for earning an Amateur Radio
license vary depending on which country you live in.
Many hams enjoy learning about radio technology, often though
building their own equipment or antennas,
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
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
Peter
Parker's Project Page - A collection of homebrew projects for the amateur radio
enthusiast. A few projects include full constructional articles, but most have just
schematic diagrams and a few notes.
Practical Security
in TETRA - At the moment many TETRA systems are being realised. Within most of the
systems, security is an important practical aspect of the implementation. As the
discussion of application of TETRA in military systems has started it can be expected that
security aspects for TETRA become even more important. This document explains the
management of some of the most important TETRA security features. This document is a
zipped word document.
Sound Card
Interface with Tone Keyer - This is an improved version of the audio interface
commonly used to connect a PC's soundcard to a transceiver's receive and transmit audio
circuits for PSK31, SSTV, . The usual version of this type of interface (including the
commercial "RigBlaster") requires the use of a serial port to provide PTT
(push-to-talk) control for the radio's transmitter. This version includes an audio tone
detector that keys the transmitter whenever transmit audio is generated by the application
running on the PC.
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.
Understanding
Power Splitters - how they work, what parameters are critical, and how to select the
best value for your application
Understanding
Soundcard Interfacing - This page is an attempt to correlate the interfacing schemes
for various Radio models, and Sound Card configurations.
www.mods.com - www.mods.com is the
biggest WWW sites on internet for tips, tricks, and modifications of HAM rigs, HAM modems,
etc. Here you will find modifications of all types of HAM radios and HAM modems etc.
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.
Typical radio equipment (transitters and receivers) are designed for
50 ohm impedance (many consumer radio receivers and TVs are designed for 75 ohms
impedance). An ideal antenna solution has an impedance of 50 ohm all the way from the
transceiver to the antenna, to get the best possible impedance match between transceiver,
transmission line and antenna. Since ideal conditions do not exist in reality, the
impedance in the antenna interface often must be compensated by means of a matching
network, i.e. a net built with inductive and/or capacitive components.
Antenna matching is essential in transmitting circuits. If the
antenna is not suitable for the transmitted frequency and transmitter impedance, the
result is very much reduced performance and even a transmitter damage (usully with high
power transmitters).
In receiving the antenna quality is not so critical if maximum
performance is not needed. If the antenna is not optimal, the received signal is just
weaker than with optimal antenna.
General
About TV and FM
Antennas - TV and FM Antenna Tips, FAQ, Reception Help, Interference and Amplifier
Guide, etc.
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
Antennas - some
basic information and resource links
Antennas,
some rules of thumb for beginners - Every now and then somebody asks for antenna
suggestions. Quite often these people asking about antennas are beginners who are afraid
of making the wrong choice - a contibution on antennas by James R. Duffey KK6MC/5 aka Dr.
Megacycle.
Antennas
- An antenna can be a piece of metallic wire, placed in some high items. It can be between
some trees or towers.
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
Guide
to Scanner Antennas - There have been many questions regarding how to select an
antenna for scanning. This is a Readers Digest version of antennas, meant to give new
users some idea of the different antennas and their good and bad points. At the end, there
are some specific recommendations on how to build a general purpose VHF/UHF antenna
system.
How
to make a ground plane - This picture describes ground plane arrangement for 150 MHz
frequency antenna
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.
Jim's Notebook - all
sorts of interesting and useful antenna data, techniques, hints and such
Matching
Impedances With Your Equipment - If the transmitter output impedance is different from
the impedance of the feed line connected to it, the transmitter probably will not operate
very well. Most transmitters have an output circuit designed for a 50 ohm load, but not
all antennas and feed lines will present a 50 ohm load. In this case, an
impedance-matching device is needed to provide the proper impedance correction.
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.
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
Putting a
Balun and a Tuner Together - A balun is a transformer that converts an AC signal from
balanced to unbalanced, or vice versa. This document has information on antenna baluns and
their use.
RF Coaxial
Connectors - RF coax(ial) connectors are a vital link in the radio spectrum. Coax
connectors are often used to interface two units such as the antenna to a transmission
line, a receiver or a transmitter. Coax connectors come in many impedances, sizes, shapes
and finishings. There are also female and male versions of each. As a consequence, there
are thousands of models and variations, each with its advantages and disadvantages. The
proper choice of a coax connector will facilitate this interface.
Signal
Cabling - quite often the humble feed line is to blame if the communication does not
work
Weatherproofing
Andrews Connectors - Andrew connectors are designed to be pretty weatherproof by using
tight tolerances and O-ring gaskets in a couple of places. It is ALWAYS a good idea to
weatherproof any connector joint; in fact, it is done practically 100% of the time by
professional installers.
Antenna building projects
2304 Tech List - Many radio
atenna building project documents on-line. Pages have also many radio equipment plans
on-line.
A UHF Discone
Antenna for scanners - The availability of scanners and wideband receivers covering
the upper UHF spectrum above 800 Mhz necessitates reasonably priced, wide bandwidth,
effective antennas. The most commonly used arrangements for wideband reception on scanners
using an outdoor antenna system are multiband trap antennas, a discone, or a simple ground
plane antenna.
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.
Radial Wire Antennas
- The Radial Wire aerial is simply a length of wire laid on the ground in a straight line.
Radial Wire aerials are a very simple and easy way of obtaining amazingly good radio
reception on longwave, mediumwave and the lower shortwave bands.
Tikapuu-antenni
- This is an antenna for 27 MHz. The text of this document is in Finnish.
Active antennas
Active Antenna I -
This circuit shows an active antenna that can be used for AM, FM, and shortwave (SW). On
the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. This
circuit is designed to be used on receivers that use untuned wire antennas, such as
inexpensive units and car radios.
Active Antenna II
- This circuit is designed to be used on receivers that use untuned wire antennas, such as
inexpensive units and car radios.
Active Antenna III
- This circuit is designed to be used on receivers that use untuned wire antennas, such as
inexpensive units and car radios.
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
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 1650Kh
TV antenna
amplifier - covers the frequencies from 40 to 900 MHz, suitable frequency rage for FM
or TV antenna amplifier
UHF-TV
Booster - This is a UHF-band TV pre-amplifier which uses special HF transistors ,
BFQ85 or BFR90.
Antenna baluns
Baluns are sonverters which convert the unblanced antenna signals
from coaxial cable to a blaanced format suitable for antenna types which need balanced
signals (for example dipole antennas). Besides this conversion the baluns will quite often
do some form of impedance conversion in the process.
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
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.
LC
Filters - This is a step by step, easy to follow and duplicate electronic tutorial on
the design of LC Filters for your electronic project, ranging from the quite simple to the
very complex, to incorporate into your next radio design.
Fixed
Attenuators - Fixed attenuators can be designed to have either equal or unequal
impedances and to provide any amount of attenuation (theoretically) equal to or greater
than the configuration's minimum attenuation - depending on the ratio of Z1/Z2.
Attenuators with equal terminations have a minimum attenuation of 0 dB. Unequal
terminations place a lower limit on the attenuation.
Simple
Field Strength Meter - simple and also quite sensitive, uses an ordinary digital
voltmeter to measure signal strength, works on VHF and FM bands
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
Amateur
Vertical Antenna Calculator - This calculator is designed to give the vertical length
(height) of a particular antenna, for the frequency and wavelength chosen.
Aircraft
Receiver - A passive receiver for listening to the pilot, pdf file
AM radio circuit (by
Fran Golden) - This AM radio circuit will demonstrate how a radio wave is received and
detected, using a very simple tuned radio frequency design.
A Short
Wave Regenerative Receiver Project - A regenerative radio receiver is unsurpassed in
comparable simplicity, weak signal reception, inherent noise-limiting and agc action and,
freedom from overloading and spurious responses. In the comprehensive electronic project
presented here, Charles Kitchin, N1TEV has provided us with a three stage receiver project
which overcomes some of the limitations of this type of receiver, principally the
provision of an rf amplifier ahead of the detector.
Compact
20: A 14 MHz Direct Conversion Receiver - This is a no-frills homebrew direct
conversion receiver that is capable of receiving local and overseas stations on the
popular 14 MHz band. The well-known NE-602 is used as the product detector. A MPF102 RF
amplifier assures adequate sensitivity. The audio stage uses the common 741/386
combination. Component values provide high and low frequency roll-off suitable for SSB
(can be mofied for CW also). This set is ideal for portable use because of its low power
consumption.
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
Simple AM
Radio Receiver & Amplifier - This is an extremely simple AM radio receiver and
amplifier circuit which is capable of driving a small, 8 ohm speaker. Construction is
simple and could be performed on a breadboard with decent results.
Simple Op-Amp Radio
- This is basically a crystal radio with an audio amplifier which is fairly sensitive and
receives several strong stations in the Los Angeles area with a minimal 15 foot antenna.
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.
Estimating
Transmitter Distance - Here you can find a simplified equation for analysing low power
radio transmitters, for line of sight. It does not take into account probagation
conditions or other limiting factors, but does include a variable for the losses in the
antenna and tank circuit of a transmitter.
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.
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.
VHF Pirate
Radio Electronics - This document explores the concepts involved in radio broadcasting
relevant to the pirate radio operator on VHF FM. This document give a step by step tour of
a typical VHF FM transmitter system starting with the output from the tape recorder or
mixer, and finishing with a brief discussion of aerials.
4
Transistor Transmitter - provides an FM modulated signal with an output power of
around 500mW at around 100 MHz
Basic
FM Transmitter - This transmitter is designed for FM broadcast band, 2 meters, and
other VHF bands by changing values of one capacitor and one coil.
Coil-less FM
Transmitter - Very crude transmitter which uses the 9th harmonics of 10.7Mhz
(96.3Mhz).
FM
Beacon Broadcast Transmitter (88-108 MHz) - This circuit will transmit a continuous
audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or
security purposes. Circuit draws about 30 mA from a 6-9 volt battery and can be received
to about 100 yards. A 555 timer is used to produce the tone (about 600 Hz) which frequency
modulates a Hartley oscillator. A second JFET transistor buffer stage is used to isolate
the oscillator from the antenna so that the antenna position and length has less effect on
the frequency.
FM Oscillator
With BF900 Dual Gate Mosfet - This is a 100 MHz frequency FM transmitter circuit
designed aroun BG900. Instead of the BF900, a BF905 or BF907 can be used without any
problems. This circuit uses 15 V DC power (50 mA) and outputs RF output of around 55 mVpp
to 50 ohm load. This circuit has a low frequency deviation.
Low Power FM
Transmitter- This circuit operates from 9V battery and transmits FM signal at
frequency range around 90-108 MHz. This circuit can take microphone or line level signals
for modulation.
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
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. This plan is based on Velleman kit circuit which is slightly modified
(this article has a new circuit board design).
Mini FM transmitters take place as one of the standard circuit types
in an amateur electronics fan's beginning steps. When done right, they provide very clear
wireless sound transmission through an ordinary FM radio over a remarkable distance
Coilless FM
transmitter - This is a circuit which transmits the signal from microphone at 96.3Mhz
band. This circuit uses a 10.7Mhz ceramic filter as frequency standard reference.
Simple
FM transmitter with a single transistor - This simple FM trasmitter works on 1.1-3 V
supply (1.8 mA current @ 1.5 volts). This circuit gives around 30 meters range and has a
built-in elecret microphone.
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.
2400MHz Signal Source
- This unit is an attempt to make the simplest possible signal source for 13cm without the
usual grief of not finishing up on the right frequency. The oscillator starts with a
readily available 96MHz crystal and multiplying this by 25 goes up to 2400MHz. The use of
filters takes the guesswork out of finding the correct frequencies. The output is -10dBm
(100 microwatts).
FM
Oscillator - circuit for a VCO and buffer that operates across the entire FM broadcast
band (88-108 MHz)
Low-cost
relative-humidity transmitter uses single logic IC - This low-cost
percentage-relative-humidity radio transmitter operates in a cold-storage warehouse for
vegetable storage at temperatures of 1 to 5°C. The transmitter design is simple: It uses
a readily available, capacitor-type percentage-relative-humidity sensor for which the
capacitor value increases with humidity. The circuit can be tuned to operate at 10- to
50-MHz RF band.
Low Power MW
Transmitter - This very low power MW transmitter is designed to take audio from the
headphone socket of any hi fi, cd player etc. The audio is used to modulate a carrier
which can be tuned to any part of the medium wave band.
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
SSB
Modulator - generates SSB signals from 35MHz to 80MHz
THE
FOX750: 750 milliwatt transmitter - This three transistor 144 MHz transmitter uses a
48 MHz scanner crystal as an oscillator / tripler. A second transistor boosts the signal
to 40 milliwatts, a third amplifies the power output to 750 milliwatts.
UKW Sender - operates from
one 1.5V battery, lacks some coil information
You might have seen people at the park flying a model airplane or
blimp, or controlling a miniature boat sailing serenely across a pond. You might wonder
how this works. This kind of devices use radio controlling. The operation principle of the
radio control is that the transmitter sends a control signal to the receiver using radio
waves. The control signals are sent in some suitable coded form (many different codes for
different uses exist). Besides remote controlled toys radio controlling can be used in
very many other applications when some remote device needs to be controlled without wires.
RC toys typically have a small handheld device that includes some
type of controls and the radio transmitter. The transmitter sends a signal over a
frequency (most RC toys operate at either 27 MHz or 49 MHz) to the receiver in the toy.
The majority of RC toys are labeled with the frequency range they operate in. Most
full-function controllers form simple have six on/off-type controls. Controllers for more
advanced RC systems often use dual joysticks with several levels of response for precise
control of RC servo motors in the controlled device.
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
Radio modems allow digital data communications through radio waves.
The radio-modem, although usually much slower than its telephone counterpart, has the
in-built capacity of being a self-correcting data carrier. The deterioration of the speed
of transfer in bad conditions can become annoying to the impatient operator.
Radio modems are available usually in teo different formats. Some
modems are devices which contains the modem part and radio transceiver as a single device
or module. The other kind od radio modems are modem devices which are designeed to to
interface to a normal "voice communication" radio or similar device (uusally
through headphone, microphone and PTT connections).
The most common modem modulation method for radio communications use
is some form of FSK (Frequency Shift Keying). This type of modulation passes nicely
through many kinds of radio radio based "voice channels". Simple FSK modulation
through few kHw woice band channel can usually give transfer speeds up to 1200 bps or 2400
bps. For more speed some more advanced modulations are needed. Those fster communication
modulation methods need to be optiomazed for radio communication (modulations used in fast
telephone modems are optimized only for telephone line and usually perform very poorly on
radio channel).
Many commercial radio modems provide a simple wireless link with the
ability to send any message protocol at any data rate up to the maximum quoted. They
provide a simple means of passing RS232 data streams with no message overhead in the form
of extra addressing or error-checking codes. Generally with this kind of modem when there
is enough signal strenght and not much interference, data supplied to the transmitter
input is reproduced at the distant receiver's output. When operating near the limit of
maximum range will the received output be prone to data corruptions. The transmitter is
usually switched on by asserting the transmitter control line. A short delay (varies
dependign on device type used) is required to allow the transmitter and receiver to
establish the link before any data can be sent. When the transmitter is switched off at
the end of a message, a short burst of noise may occur before the receiver's mute operates
(this noise should be ignored by the system connected to the receiver).
In radio communications the user may need to provide error checking
and/or addressing to each mesage if the application requires guaranteed data integrity.
When using radio communication some for of error checks, error correction, and
re-transmission methods are very often needed to be able to get reliable communication
over noisy radio channels. This noise on radio channel causes transmission errors which
needs to be corrected by mode or handled in some way by the communication protocol itself.
The needs vary depending on the transmission distance, available signal power, radio band
used and radio modem type.
The free space propagation signal propagation rule for radio
communications is that a 6dB change in transmitter power is required to double / halve the
range. An imperial 'rule of thumb' for in-building operation requires a 15dB change in
path loss capability to change the range by a factor of two (hhis is a very cruel law).
There are international and national bodies that allocate frequency
bands and issue authorization to transmit signals. In some countries, there are bands that
are allocated for public use without the need for any special authorization. This is an
important factor to consider when selecting a radio modem, since getting authorization to
broadcast information is often not an easy task. The bands that are allocated for public
use are of particular interest. The 900 MHz band in the United States and 2.4 GHz in most
European countries are allowed for spread spectrum communication without any special
authorization (but there are limitations on the amount of power that one can use to
transmit signals). In Europe there are also frequencies 418MHz and 433.92MHz for low power
short distance licence exempt communications (there are ready made modules available for
this, check your country regulations if their use is allowed in your country if you live
in Europe).
General information
Data Radio Standard Test
Methods Project - A project to establish Standard Test Methods for the evaluation of
radios used in data communications especially aimed at Amateur Packet Radio.
Federal Standard 1052
- This standard is one of a series of standards pertaining to automatic high frequency
(HF) radio equipment and operation. The basic standard is Federal Standard (FED-STD)
1045A, Telecommunications: HF Radio Automatic Link Establishment.
Introduction to
Packet Radio - Packet has three great advantages over other digital modes:
transparency, error correction, and automatic control. The operation of a packet station
is transparent to the end user; connect to the other station, type in your message, and it
is sent automatically. The data on acket radio system is usualy sent using radio modems.
AX.25 (Amateur X.25) is the communications protocol used for packet radio.
Nowadays there exists radio modem software for PC which uses PC
soundcard as the signal input and output device. Here you can find information how to
interface PC soundcard to your radio.
Radio Interface
- This uses computer and ICOM 746 to transmit and receive audio signals using the sound
card to create and decode the transmissions.
Sound Card
Interface with Tone Keyer - This is an improved version of the audio interface
commonly used to connect a PC's soundcard to a transceiver's receive and transmit audio
circuits for PSK31, SSTV, . The usual version of this type of interface (including the
commercial "RigBlaster") requires the use of a serial port to provide PTT
(push-to-talk) control for the radio's transmitter. This version includes an audio tone
detector that keys the transmitter whenever transmit audio is generated by the application
running on the PC.
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
AM Modulator -
This circuit is a AM modulator which has been constructed by single Motorolla IC , MC1595G
or MC1496G.
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
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
FM Pre-Emphasis -
FM broadcasting in the United States requires a 75us pre-emphasis for proper frequency
response at the receiver. This is a high-precision pre-emphasis module that goes in front
of the main broadcast limiter, but after the optional sibilance limiter.
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
FM-only radios
- Very complete radio collector's site of FM only radios. Site include historical
information, theory, photographs, and a few unique projects.
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
