:roll: High Quality Audio over 12.5kHZ Bandwidth UHF/VHF Radio Channel

High Quality Audio over 12.5kHZ Bandwidth UHF/VHF Radio Channel

Hi everybody,
I want to transmit high quality sound (not only speech, especially music) over UHF radio. In my country, bandwidth is limited (12.5kHz) because of goverment rules.

I found an UHF radio modem that uses 64-QAM modulation achieves bitrate of 60 kbps in 12.5 kHz; 120 kbps in 25.0 kHz bandwith.

I want to ask you, is there any low cost solution rather than using a digital modem? Or is there any way to make a Do-it-yourself solution for transmitting quality rich (0-18kHz) sound over 12.5 bandwith limited radio channel?

I want to understand may i design a transmitter that use 64-QAM ? Is this possible or how can i find a low cost solution for this? :thinker:


Design considerations:
1- VHF/UHF dual band radio
2- RF Transmitter power limited to 5Watts (Max)
3- Audio quality to be transmitted must be High Quality (20Hz ~ 15kHz or 32kBit/second bit rated compressed digital audio)
4- Modulation must be high symbol rated (64-QAM or something like that.)


Do you have any (low cost solution) idea?
Thanks.!

I can't be sure about radio broadcasts, but in the computer world, for stereo hi-fi, 128 kbps is about the minimum you need.

When converting FM stereo broadcasts to mp3's, I saw a comparison article state that they filter out audio information above 15 kHz, and therefore 96 kbps is a sufficient bitrate. So that's what I use.

Youtube videos provide a much lower bitrate for the audio portion. Nevertheless it is listenable for millions of viewers.

So you may find it is adequate to have a bitrate of 60 kbps (stereo). It will not be top-notch fidelity, but it should be listenable.

It is possible, in fact some DRM radio stations are using 12KHz bandwidth to transmit very reasonable stereo programs in the MW and SW bands and they have HTML program anouncements too.

It isn't something for a beginner though and I don't think any simple electronic solutions are available.

Brian.

betwixt said:

It is possible, in fact some DRM radio stations are using 12KHz bandwidth to transmit very reasonable stereo programs in the MW and SW bands and they have HTML program anouncements too.

It isn't something for a beginner though and I don't think any simple electronic solutions are available.

Brian.

Click to expand...

O brother... Thank you very much for sharing your knowledge. :idea:
Now i am looking a way to transmit DRM modulated signal over VHF or UHF frequency on mobile radio.

I warned you it isn't easy but if you want to try, look for a program called DRMDream, sometimes shortened to just 'DReaM'. You should note that DRM is a licensed technology which you are supposed to pay for. I have a licence but it dates from so far back that I can't remember what it cost me.

Brian.