Transceiver Circuits

A transceiver is a device that has both a transmitter and a receiver which are combined and share common circuitry or a single housing. Similar devices include transponders, transverters, and repeaters.

In radio terminology, a transceiver means a unit which contains both a receiver and a transmitter.

It was quite common to have these units separated. Ham radio operators can build their own equipment and it is always easier to design and build a simple unit having one of the functions, transmitting or receiving. Almost every modern amateur radio equipment is now a transceiver but there is an active market for pure radio receivers, mainly for shortwave listening operators.

The term originated in the early 1920s. Technically, transceivers must combine a significant amount of the transmitter and receiver handling circuitry. An example of a transceiver would be a walkie-talkie, or a CB radio.

A walkie-talkie (more formally known as a handheld transceiver) is a hand-held, portable, two-way radio transceiver. If no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola.

Similar designs were created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work. Major characteristics include a half-duplex channel (only one radio transmits at a time, though any number can listen) and a "push-to-talk" (PTT) switch that starts transmission.

Transmission indicator

Everytime the push-to-talk button is closed the light will go on. The antenna samples the output RF from the transmitter. That signal is then rectified (detected) by germanium diode Dl, and used to charge capacitor C2. The dc output is used to trigger a small silicon-controlled rectifier (SCR1), which permits the current to flow through the small pilot lamp...

Tr circuit

R1 and R2 are Va or Vi W carbon composition resistors. K1 is a 12 V DPDT DIP relay. Illustration A shows how to connect the relay contacts for use with a separate transmitter-receiver combination. The circuit at is for amplifier use with a transceiver. ..

Simple Am Radio

An AM radio can be built of a simple diode detector and an audio amplifier. A random length of wire always serves as an ant..

Relay Interface For Amateur Radio Transceivers Circuit

The relay power in the linear is obtained from the -120-V bias supply, and the transmit keying output from the Kenwood is +12 V at 10 mA maximum. The key ingredient in the circuit is the pnp driver transistor,..

RS485 Transceivers

Recent innovations in process and circuit design have enabled the release of three new RS485 transceivers: the LTC®1481, LTC1483 and LTC1487. These devices share an improved receiver circuit which features 80mA quiescent current operation (driver disabled) with no loss in AC performance relative to standard RS485 devices, and a new 1mA shutdown mode (Figure 1)...

RS232/RS485 Multiprotocol Transceiver

The LTC®1387 is a single 5V supply, single-port, logic-configurable RS232 or RS485 transceiver. The LTC1387 features Linear Technologys usual high data rates (120kBd for RS232 and 5MBd for RS485), a loopback mode for self test, a micropower shutdown mode and ±7kV ESD protection at the driver output and receiver inputs. This part is targeted at handheld computers, point-of-sale terminals and applications that require a minimum pin count and software-controlled.....

Transciever Relay Sequencer

When the sequencer is not activated (The radio is receiving) K1 is in its N\C position, suppling DC voltage to L1 forward biasing D6, D7 and then flowing through R13 and R14 (As shown in blue arrows). C3 and C4 are used to block the DC. Once D6, D7 are conducting the RF signal is able to pass from the RX IF port to the radio input / output port (As shown in red). When the sequencer is activated (The radio is transmitting) K1 is in its N/O position suppling DC voltage to L2.....

HF phone rig for 20-40 meter band

A simple project, within most of homebrewers capabilities. Very simple tuning, a single stage to align, besides VFO frequency adjusting. Easy to find, cheap components. Reduced dimensions and low power requirement, a totally portable rig. It's worth while to spend some words about the DSB modulation. It's simply a type of amplitude modulation (AM). It is common knowledge that an AM signal is composed by a carrier and two sidebands, wich take the whole information. The.....

@Buffered Crystal VXO

The circuit is an VXO with buffered output. It operates on 20-meter amateur radio band with the output voltage about 0.2 Vp-p. The crystal frequency is pulled by tuning the variable capacitor CV1 about 36Khz with only one crystal (Y1), and 250Khz by using two crystals Y1 and Y2. The first configuration stability is much better than using two crystals. However, if you need more frequency variation, use two crystals and you have to pay the cost by getting less stability. ..

RS485 Transceivers Sustain ±60V Faults

The LT®1785 and LT1791 RS485/RS422 transceivers with ±60V fault tolerance solve a real-world problem of field failures in typical RS485 interface circuits. Modems and other computer peripherals use point-to-point RS422 connections to support higher communication speeds with better noise immunity over greater distances than is possible with RS232 connections. Multipoint RS485 networks are used for LANs and industrial control networks. All of these applications are.....

RS485 Transceivers at 52Mbps Over Twisted Pair

The LTC1685 is geared for half-duplex operation, whereas the LTC1686/LTC1687 can operate in full-duplex mode. All include a receiver fail-safe feature, whereby the receiver output remains in a high state over the entire 12V to 7V common mode range when the inputs are left open or shorted together. A novel protection technique permits indefinite short circuiting of the driver and receiver outputs to supply or ground, while limiting the current to 20mA...

Isolated RS485 Transceiver

The RS485 interface standard is designed to handle a 7V to 12V input signal range; however, in practical systems, ground potentials vary widely from node to node, often exceeding the specified range. This can result in an interruption of communications, high current flow through ground loops or worse, destruction of a transceiver. Guarding against large ground-to-ground differentials calls for an isolated interface. A new surface mount device, the LTC®1535.....

40 Meter CW/DSB Transceiver

It uses 22 each 2N2222`s and will run from 12 Volts. The Receiver is a direct-conversion design with a switchable input attenuator and RF preamp, diode balanced mixer (diodes were allowed), a switchable low-pass-band-pass passive filter, and audio amplifier. (I may replace the audio final with the version presented by K8IQY, which I like much better). The Local Oscillator also serves as the VFO during transmit. The oscillator is a Colpitts design with varactor tuning, and.....

7MHz SSB TRANSCEIVER

The circuit uses easily available components. Most of the coils are wound on low cost balun core. The circuit uses ladder filter. Filter is build around four numbers of 4.43 MHz crystals. I used ladder filter because it is cheap and getting reasonably good reports. The circuit uses two numbers of MC1496. First MC1496 functions as receiver mixer cum balanced modulator. Second MC1496 works as product detector cum transmit mixer. The block diagram of the transceiver is.....

LASER Transmitter/Receiver

This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc..). The whole thing is very easy to build and requires no specialized parts execpt for the LASER itself...

5 watt, 80 meter QRP CW Transceiver

1. Full 5 watt output using a power MOSFET final that is resistant to high SWR and thermal runaway. This final is very efficient and runs much cooler than traditional bipolar designs. 2. Highly sensitive and selective superhetrodyne receiver with plenty of audio to drive a speaker. About 100 Khz of tuning range is provided through a varactor diode along with a switchable RIT control. 3. Full break-in keying with a unique T/R switching.....

RS-232 Laser Transciever circuit

Laser based projects used to be expensive, until the development of solid state lasers. This project is designed for the entry level laser experimenter. The circuit allows any two computers with serial (RS-232) communication capability to communicate over 200 meters using a laser beam. A low cost transmitter only circuit is also presented here for use in one way communication and other laser based projects. If you are like me and always wanted to buy a laser pointer to.....

40 meters CW Transceiver

This project describes a little QRP transceiver full legal power” (5 W at 12 V) for the 40 meters band. The RIG may be built in a gradual manner, in fact it is divided in two main modules, or you may also complete only the RX module. The RX section is designed so as to allow receiving both SSB and CW signals on the whole 7 MHz band. The tuning may be done using only an HF receiver, but if you have at your disposal a frequency meter and a signal generator, you could.....

2m VHF FM PMR transceiver to amateur radio converter

The PMR VHF transceiver Motorola Radius M110 (in further text referred as M110) was manufactured by Motorola GmbH therefore being an European radio. Since many professional radio service users has replaced this transceiver with newer gear, a considerable number of M110 has appeared on HAM flea markets. M110 is a simple yet fine transceiver with pretty good receiving performance and it would be a waste to throw it away or to use it just as a source of electronic components.....

Mains Remote Tranciever Alarm

Pressing the pushbutton of the transmitter, a sound and/or light alert is activated in the receiver. The system uses no wiring or radio frequencies: the transmitted signal is conveyed into the mains supply line. It can be used at home, in any room from attic to cellar, simply plugging transmitter and receiver in the wall mains sockets. Transmission range can be very good, provided both units are connected to the mains supply within the control of the same light-meter...