[Ham-Mac] Mac - SignaLink - CocoaModem

[Jack Brindle]

No no no no!!!!!

The Signalink USB contains a USB Audio interface chip. This chip provides both A/D and D/A codec functions. It is powered directly from the USB. On one side it communicates with the computer through the high-speed USB (12mbit I believe) and on the other it interfaces with the radio's speaker and mic ports. Just one chip handles the whole thing. There may be a second to provide the VOX function.

I'm not sure what the power switch is for on the Signalink, it seems to just turn on and off the power LED. But, my Signalink USB also converts received signals into USB data when that switch is off. I'm not sure if it enables/disables the VOX.

The key here is that the device is powered from the computer or USB hub. There is no magic, just one or two ICs.

Jack Brindle, W6FB

On Jun 19, 2012, at 3:45 PM, Alan Bomberger wrote:

> Ok,  I guess I thought that sound cards contained A2D and D2A converters.
> I guess this USB sound "adapter" just gets the signals onto the
> USB bus and the Digital/Analog stuff is done in software.   I can
> live with that.  Still doens't quite explain why the input signal
> level is considerably higher with the power on..
> 
> Thanks for the info!!
> 
> 
>> On Jun 19, 2012, at 2:33 PM, Alan Bomberger wrote:
>> 
>>> How is it that CocoaModem (and fldigi) can read signals from the
>>> SignaLink when the Signalink power is off?   I noticed this the
>>> other day when I went to answer a CQ and the transmitter didn't go
>>> on.  No Power, No PTT.  Granted the receiver input is much lower than
>>> with power on but what is running the ADC chip?
>>> --
>>> It is seldom that liberty of any kind is lost all at once. - David Hume
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>> 
>> I am quoting from memory but as I recall the only active (or 
>> powered) circuit in the SignaLink is for the Auto-PTT.  It is almost 
>> passive for RX; however, when I had one I noticed some minor Rx 
>> attenuation and this was confirmed by Tigertronics.
>> 
>> Dick AA5VU
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> 
> -- 
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