Difference between transceiver and transponder ?

[DigiTan]

Here's a question that been bugging me for a while. What's the difference between a "transceiver" and a "transponder?" Normally, I see "transponders" associated with microwave communications (and more recently, RFID gear), but the terms still seem interchangeble. Is there something I'm not getting here? :?

 

[Pommie]

Transceiver, a combined transmitter and receiver. ie. walky talkies. Bluetooth adapter, a MAX232 level shifter.

Transponder, a device that when interrogated will respond with the relevant information. For example, a digital temperature chip will reply with a data stream that represents the temperature when commanded to do so. An aircrafts transponder will report the call sign and height of an aircraft when interrogated by an airport radar (squawk and mode C for any pilots present :roll: ).

Neither have to be radio. Both could be radio, IR, ultrasonic, sonar etc.

Mike.

 

[David Bridgen]

What's the difference between a "transceiver" and a "transponder?"

The word "transceiver" is a contraction of (radio) transmitter-receiver, so it is a device which contains both. A "walkie talkie" is one example, a cell phone is another. The former is a simplex device. You can either listen or talk. To talk you have to operate a switch or button and only one party can speak at a time. The cell phone is a duplex device, just like a wired telephone. Both parties can supposedly talk at the same time.

A transponder is a device which responds to an interrogation and needs no human intervention. When it receives a demand it responds with certain information. One example is used in aircraft. An air-traffic control centre will instruct a pilot to set his transponder to a four-digit code while he is within that centre's airspace. When the transponder is interrogated by ground radar it replies with various data such as aircraft i.d. and altitude.

Another transponder is the r.f.i.d. tag which has been receiving attention from the press recently.



Hi, Pommie. You posted while I was composing my reply and I didn't check before pressing Submit. I'm not trying to steal your thunder.

 

[Dean Huster]

And with these interesting definitions, where does that put the typical amateur radio repeater?

Dean

 

[Nigel Goodwin]

And with these interesting definitions, where does that put the typical amateur radio repeater?

I would say they are a transponder!. Broadcast TV satellites are also transponders, they receive a signal and rebroadcast it back to earth, and are actually called transponders in the trade.

Certainly in the past 'transponders' only seemed to be used for data purposes, such as ID transponders in aircraft, which give the aircrafts indenification on radar screens - but, by definition, should probably apply just as well to voice or picture retransmissions.

 

[David Bridgen]

And with these interesting definitions, where does that put the typical amateur radio repeater?

I think they stand on their own, with their own definition, as do military re-broadcast stations. I see no need for them to be put in either of the former categories.

 

[DigiTan]

An aircrafts transponder will report the call sign and height of an aircraft when interrogated by an airport radar (squawk and mode C for any pilots present :roll: )

So that's how those work! :lol: Thanks for the help guys! This really cleared things up.

 

[stevez]

A repeater receives input, often on one or more fixed frequencies, then retransmits it on a fixed frequency. A transponder receives within a band of frequencies - and retransmits within another band or 'window'. If you are using a repeater and you shift your transmit frequency the output of the repeater does not shift - and at some point the repeater receiver won't hear you. If you shift your transmit frequency somewhat (within limits) to a transponder the output of your signal from the transponder will shift as well. Amateur satellites typically use transponders.