[Yaesu] Digital modes through FT100 mic jack

[Dr. Gerald N. Johnson]

Line level is about 60 db too strong for the microphone input. And the 
microphone input is touchy about ground loops from the computer. You 
need an isolation transformer and lots of attenuation. The transformer 
from a retired 300B to 28KB PC internal modem card is just perfect. The 
FT100 microphone needs DC for the electret and maybe the phone tones to 
work. So there is DC on the jack. I don't know if there's DC on the 
audio input wire but there could be and then you will need a coupling 
capacitor also. I'd put the attenuation on the transmitter side of the 
isolation transformer so any hum it would pick up from power supply or 
old fashioned fluorescent ballasts would be attenuated before getting to 
the transmitter audio input.

Speaker level may also be a bit strong for the line input. Its a nice 
feature of the 857 and 897 that there is line level IN and OUT on the 
minidin data connector out back. And doesn't need isolation, just a 
connecting cable.

73, Jerry, K0CQ

On 4/21/2013 9:02 PM, John G. wrote:
> It is fairly easy to run a cable between the mic jack on the FT100 and the line out jack on a computer (turn on the VOX) and run AFSK that way, or is it more complicated.  I seem to remember hearing that the FT100 needed some voltage or something on the mic line, but I could be wrong with that also.  Has anyone been able to run AFSK this way?
>
> I am trying to come up with a cheap interface for the digital modes, and my netbook doesn't have any serial ports.
>
> 73 John AF5CC
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