Walkie-talkies provide a cost-effective alternative for cellular phoneuse 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 buttonto instantly speak to your group. Most ypical control in walkie-takie radio is CHANNEL, which is used to select the desired channel.Many walkie-talkie systems involve some form of SQUELCH system. If the walkie-talkie picks up unwanted, partial, or very weaktransmissions, turn SQUELCH clockwise to decrease the walkietalkie's sensitivity to these signals. Turn SQUELCH counterclockwise if you want to listen to a weak or distant station. General operation advice for using walkie-talkie radio is to hold the walkie-talkie 2 or 3 inches from your mouth. Press and hold down the transmit speak into the microphone in a normal voice. In most systems the walkie-talkie's automatic modulation circuit adjusts themicrophone's sensitivity to allow a wide variety of voice levels. Do not speak too loudly when transmitting. It does not makeyour signal any stronger, and might distort your transmission.
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
Directive - 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).
- Two
Way Radio Directory - A
comprehensive directory of Two Way Radio
resources with over 1500 links
Technology
- CTCSS
(Continuous Tone Coded Squelch System) -
CTCSS (Continuous Tone Controlled
Squelch System) a sub audible tone in
the range of 67 to 254 Hz.
- CTCSS,
PL, Tone Squelch, and other Necessary
Evils
- 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.
- ETSI's
forthcoming DIIS standard - New
standard proposal for digital radio at
PRM446 frequency band
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.
-
Citizens Band Radio Service
- Citizens Band (CB) Radio Service is a private two-way voice communication service for use in personal and business activities of the general public. Its communications range is from one to five miles.
The Citizens Band (CB) operating at 27
MHz has been used in many European
countries. Those devices has been called
with names like LA, CB and PR27. The LA
version is amplitude modulated and PR27
version is FM modulated. In many countries
operating CB radio needs a license. Here is
short introduction to different versions
(based on sitation in Finland, some
specfications can vary in other countries):
- LA: Channels 1-22 and 11A, AM or FM
modulation, 5W power
- PR: Channels 1-40, FM modulation,
power 4W
- CB: Channels 1-40, AM/FM/SSB
modulation, power levels: 4W FM, 1W AM,
4W SSB
Nowadays there is european wide directives
for this kind of deivces. This kind of
devices are marked with mark R....PR27 and
covered by telecommunications terminal
directive 1999/5/EY. This kind of devices
should also have CE mark in them. European
"EU" Band is 26.965 MHz - 27.405
MHz (ETS 300 135/MPT 1333 "CEPT/EU
Channels", total 40 channles) and
26.965 MHz - 27.405 MHz (MPT 1382 December
1997, sometimes referred as CEPT or "EU"
channels, total 40 channels). Allowed
frequency band can vary somewhat from
country to country (some countries have more
channels, so there cna be specific models
only to be used on some specific countries).
The maximum transmitter RF carrier power
output allowed is 4 Watts and the antenna is
restricted. CB radio is is voice only
service. Generally no data transmission is
allowed.
PMR446 stands for Personal Mobile Radio.
PMR446 is a European standard licence-free
radio service. PMR-446 is a licence free
communication band in Europe that anyone can
use for two-way radio communications. The
specification is largely based around the
American Family Radio Service known as FRS
that has been in existence for a few years
and have proved extremely popular as an
alternative to CB 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).The
channels for PMR446 are as follows:
Channel 1 - 446.00625 MHz
Channel 2 - 446.01875 MHz
Channel 3 - 446.03125 MHz
Channel 4 - 446.04375 MHz
Channel 5 - 446.05625 MHz
Channel 6 - 446.06875 MHz
Channel 7 - 446.08125 MHz
Channel 8 - 446.09375 MHz
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
licencedequipment. 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. The typical coverage range
of PHR446 system with 500 mW
transmissionpower is around half kilometer
to one kilometer. In very goodconditions
(for example on open sea), the coverage of
few kilometers is possible.
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. The Federal
Communications Commission (FCC) authorized
Family Radio Service in 1996 as a short
distance, unlicensed, two-way voice service
for general purpose use. Family Radio
Service is meant to be used for direct,
personal voice communications among two or
more people. FRS radios are personal two-way
(send/receive) radios which conform to the
FCC FRS specifications. In brief, they're an
inexpensive and easy way to communicate with
family and friends over short distances
(under 2 miles). FRS radios offer 14
separate communications channels, and each
channel can handle up to 38 separate
conversations or "talk groups."
Channel and talk groups are shared by FRS
radio users on a "take turn"
basis, and they cannot be assigned
exclusively to any specific individual or
organization. FRS Channel Frequency
Assignments:
Channel 1: 462.5625mhz
Channel 2: 462.5875mhz
Channel 3: 462.6125mhz
Channel 4: 462.6375mhz
Channel 5: 462.6625mhz
Channel 6: 462.6875mhz
Channel 7: 462.7125mhz
Channel 8: 467.5625mhz
Channel 9: 467.5875mhz
Channel 10: 467.6125mhz
Channel 11: 467.6375mhz
Channel 12: 467.6625mhz
Channel 13: 467.6875mhz
Channel 14: 467.7125mhz
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. Many
radio models are manufactured for both
European PMR446 and FRS in USA, and there
are very few differences apart from cosmetic
ones and channel frequencies.
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.
- TETRA
Summary
Many people constantly ask for
walkie-talkie schematics, so here is some
links on this topic. Building this kind of
circuit need expertise in high frequency
circuits and special equipment. The most
probable outcome of your attempts is that
you get tired of trying to make it working
reliably or to work at all. Well-working
walkie-talkie circuits are carefully
designed radio circuits, even though some
of them seem to be quite simple in
construction. Best ones are complex
circuits. I suggest that you choose the
easy way and buy a ready-made
walkie-talkie radios if you need this kind
of device. It will be easier to make to
work, works more reliably and is approved
to use in your country. Home constructed
ones will most propably work much poorer
than commercial ones and are illegal to
operate.
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