[Icom] Audio, Digital modes and Icom HF

[David J. Ring Jr - N1EA]

Gentlemen,

Many of the newer digital modes use Audio Frequency Shift Keying - feeding
audio tones into a SSB transceiver instead of keying the RF oscillator to
make it change.  This method has many advantages - the best being that the
frequency is done at audio level, rather than using capacitors or other
methods of changing the RF frequency.  Also multiple tones can be used.
This method produces wonderful noises!

However, what is excellent for the human voice is not always excellent for
tones.  Often circuits process or optimize the audio to enhance voice
communications.

ICOM has an accessory jack on the back of many of their transceivers for
supplying audio to the transmitter - I know that the current IC 756/Pro and
Pro2 have this.

QUESTIONS for discussion:

Is the Audio input in the back of the transceiver better for some uses?  Or
is it identical to the microphone?

I've seen that some Icom transceivers have SSB-D mode.  I have read in the
user's manual that this shuts off the microphone, but does it only turn the
power off to the microphone connector in the front of the radio, or does
this mode access the rear microphone input?

Does the rear microphone input remain active during SSB (normal) operation.

The user's manual seemed to be vague on this.

Thank you very much,

73

David Ring
N1EA

shift and David J. Ring, Jr., N1EA
http://www.qsl.net/n1ea
http://www.qrz.com/callsign?callsign=n1ea

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