[Ham-Mac] Griffin iMic

[Jack Brindle]

On Mar 1, 2005, at 1:11 PM, Dick Kriss, AA5VU wrote:

> Heads up to Kenwood TS-570 users on the iMic. I use the Griffin iMic 
> for
> sound out of the G4 only.  It was totally useless for sound into the 
> G4 due
> to a gross impedance mismatch with the audio output from my Kenwood 
> TS-570.

This is like having a 200:1 SWR on an antenna. You wouldn't expect the 
antenna/rig combination to work very well at all. The iMic has an input 
impedance in the 1K ohm range. Driving it from the 4.7 ohms out of your 
radio gives an impedance mismatch that results in an approximate 200:1 
SWR on the audio line. This really needs an impedance transformation, 
something that is commonly done with audio transformers. Try an 
inexpensive Radio Shack 1000 : 8 ohm transformer, with the 8 ohm side 
to the radio. Not only should this work better, but it will also 
provide ground isolation in case you are getting any ground loop 
problems between the computer and radio. These usually show up in the 
transmit audio.

Good luck and 73!

-Jack Brindle, W6FB
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