[Yaesu] Digital modes through FT100 mic jack

[KBØNLY]

I build a small interface that uses a 600 ohm isolation transformer and a 
600-1k multi-turn trimpot, gives isolation and attenuation to make the line 
level mic level compatible.  Works great to feed with either the computer or 
my mixer to use any of the many mics that I have.

73,

Scott KBØNLY



-----Original Message----- 
From: Dr. Gerald N. Johnson
Sent: Sunday, April 21, 2013 9:24 PM
To: yaesu at mailman.qth.net
Subject: Re: [Yaesu] Digital modes through FT100 mic jack

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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