[AMRadio] balancing highs & lows

[Nigel Holmes]

There's a rule-of-thumb that describes this. I can't remember it - maybe someone here knows it?

It gives values like (these are illustrative only!) (50-10,000Hz), (100-8,000Hz), (200-6,000Hz), (300-3,500Hz)

73 Nigel VK3DZ

-----Original Message-----
From: amradio-bounces at mailman.qth.net [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Gary Schafer
Sent: Tuesday, 26 April 2011 8:00 AM
To: stvwhite at att.net; 'Discussion of AM Radio in the Amateur Service'
Subject: Re: [AMRadio] Only function of carrier

Actually the low frequency response wastes a lot of power for communications. There is not much intelligence in the low frequencies compared to the mid frequencies. With flat audio response the low frequencies tend to take up a large chunk of the modulation percentage. This limits the modulation power in the mid range where most of the intelligence is. 
This is very evident when running the audio into a simple clipping circuit.
That is one of the reasons that low frequencies are rolled off on voice communications circuits. It allows a higher percentage of modulation of the mid frequencies where it matters.

Motorola, Collins and many others figured this out a long time ago.
That type of audio does not sound as pleasant as full spectrum audio but it is more effective for communication.

Don, K4KYP has stated many times that he rolls off his highs and lows so that the audio sounds balanced and it limits the bandwidth while still providing nice audio and no growling lows which would be present if just the highs were rolled off.

Now if you run a lot of sophisticated audio processing then much can be done to make the signal sound louder.

73
Gary  K4FMX

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