FIREPHIGHT
Member
what is this? and what does it do ?
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What is companding ???
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GrumpyGuard
Member
follow this link and it will explain in detail.
Companding
Companding
That link is only a partial explanation, where it concerns PCM multiplexing onto things like T1 telephone trunks. The A law and μ law encoding mentioned in the article are specifically used in digital telephony, A law being the European standard, and μ law being the North American standard.
In the analog world, companding is a means if mitigating the effects of a communications channel that lacks sufficient dynamic range. An example would be narrow band deviation radio systems. Compandering is used on 900 MHz trunked systems, for example. It's a means of compressing the audio wave form at transmission, and decompressing it at the receiver. The end result in both digital and analog implementations is an increased signal to noise ratio over what the communications channel is otherwise capable of providing if companding wasn't being used.
The drawback is, especially with analog compandering, what comes out on the other end isn't exactly what was sent, so there is a noticeable change in audio quality. A channel bank using μ law encoding has algorithms that do a pretty good job of putting the audio back together, although there are still some impairments that can effect certain applications. But voice sounds just fine. A compandored FM radio signal has some characteristic qualities that can be quite noticeable.
In the analog world, companding is a means if mitigating the effects of a communications channel that lacks sufficient dynamic range. An example would be narrow band deviation radio systems. Compandering is used on 900 MHz trunked systems, for example. It's a means of compressing the audio wave form at transmission, and decompressing it at the receiver. The end result in both digital and analog implementations is an increased signal to noise ratio over what the communications channel is otherwise capable of providing if companding wasn't being used.
The drawback is, especially with analog compandering, what comes out on the other end isn't exactly what was sent, so there is a noticeable change in audio quality. A channel bank using μ law encoding has algorithms that do a pretty good job of putting the audio back together, although there are still some impairments that can effect certain applications. But voice sounds just fine. A compandored FM radio signal has some characteristic qualities that can be quite noticeable.
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FIREPHIGHT
Member
ok so what your saying is this is only to be used during DTMF or can i use it any time? when i turn it on the radio sounds clear when someone its transmitting
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no, it is an audio compression that compress ALL audio when you TX and then expands it when you RX. this cleans up the signal. you do lose a little tonal quality, but with pure voice you won't hear the difference anyway. the reason it sounds better to you is it is improving the signal to noise ratio.
Compandering is also used in telco transport, which is the example given above.
Compandering is also used in telco transport, which is the example given above.
No, I didn't say that. Give us some more information to work with. What radio are you talking about? What leads you to this question? Compandoring is not something that's intended for non-technical users to have to think about, so a little background into what's driving your question might be helpful in getting an answer that's actually useful for you.
N4KVE
Member
Isn't this called "HEARCLEAR" by Motorola? GARY N4KVE
DPapay
Member
An easy to understand explanation of "companding" on an analog radio system. The radio will compress all low level audio, identifying low level as noise, and only transmit the higher level audio, identifying high level as your voice. The receiving radio does the same thing. The problem is, all the radios on the system must be set up this way, and aligned properly. If you are setting up a brand new system, this works pretty well. Not so well with an existing system.
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