11-11-2023, 11:31 AM
Hi Steve
Yes, commercial mobile communication radios use 6 dB/octave pre-emphasis at the transmit end and 6 dB de-emphasis at the receive end to restore the signal back to the original one. The pre-emphasis being used to improve the S/N ratio at the higher frequencies. This is fairly straight forward unlike in the broadcasting application.
The Broadcasting industry also plays games with speech processing especially with advertising. According to the broadcasters they said they could do noting about the high audio levels on advertising when complains were raised about this years ago. This is probably true in the sense that the advertising producers are the ones that implement the speech processing in their productions. However eventually a drop advertising high audio levels did occur though it seems to be creeping up again.
If I recall correctly a long time ago in the early of FM in amateur use, Japanese made amateur FM radios always seemed to sound somewhat different to the ex-commercial FM radios. I suspect that this was probably because they did not use any pre-emphasis on transmit. Be interesting to know if anyone else can recall this.
The original intent of my article was to address the issue of low deviation on amateur FM. I tried to keep the original article as simple as possible without delving too deeply into the finer points of FM and boring everyone with a book. Somewhat difficult to do as there are many factors that come into play.
However it is the end result that counts - the audio level that you effectively hear.
73
Igor
On a side line, years ago I was involved with the world land speed record attempt on Lake Gairdner in VK5 (Aussie Invader) with the the communications and timing. The communications from the site was HF SSB and the very early version of Mobilesat (satellite). What I found was that the the codec used then by Mobilesat had trouble dealing with my children's voices and/or the XLY's (when she got excited telling them of if they were playing up). On HF however the were no such problems were evident.
I can also to this the claim to have built the fastest talk through repeater on wheels in the world. Unfortunately I have not yet found viable market for this!
Yes, commercial mobile communication radios use 6 dB/octave pre-emphasis at the transmit end and 6 dB de-emphasis at the receive end to restore the signal back to the original one. The pre-emphasis being used to improve the S/N ratio at the higher frequencies. This is fairly straight forward unlike in the broadcasting application.
The Broadcasting industry also plays games with speech processing especially with advertising. According to the broadcasters they said they could do noting about the high audio levels on advertising when complains were raised about this years ago. This is probably true in the sense that the advertising producers are the ones that implement the speech processing in their productions. However eventually a drop advertising high audio levels did occur though it seems to be creeping up again.
If I recall correctly a long time ago in the early of FM in amateur use, Japanese made amateur FM radios always seemed to sound somewhat different to the ex-commercial FM radios. I suspect that this was probably because they did not use any pre-emphasis on transmit. Be interesting to know if anyone else can recall this.
The original intent of my article was to address the issue of low deviation on amateur FM. I tried to keep the original article as simple as possible without delving too deeply into the finer points of FM and boring everyone with a book. Somewhat difficult to do as there are many factors that come into play.
However it is the end result that counts - the audio level that you effectively hear.
73
Igor
On a side line, years ago I was involved with the world land speed record attempt on Lake Gairdner in VK5 (Aussie Invader) with the the communications and timing. The communications from the site was HF SSB and the very early version of Mobilesat (satellite). What I found was that the the codec used then by Mobilesat had trouble dealing with my children's voices and/or the XLY's (when she got excited telling them of if they were playing up). On HF however the were no such problems were evident.
I can also to this the claim to have built the fastest talk through repeater on wheels in the world. Unfortunately I have not yet found viable market for this!