This pic is the spectrum of the Griffin iMic with no input source connected.
So, I've received the Behringer UCA202 I ordered the other day. This gave very poor image rejection when immediately hooked up to my KX3's I/Q output. After some dabbling in gnuradio-cmpanion (grc), I used the UCA202 line output to feed a complex signal into its line input with a 5kHz tone. I'm only getting about 35dB image rejection when asking the UCA202 to eat its own dog food.
Some comparitive tests between the Griffin iMic (white model) and the Behringer UCA202, whereby both are forced to consume their own dog food.
The first test uses a loopback cable to feed the line in from the line out. No signal is sent to the line out of the soundcard.
Here is the Griffin iMic
Now for test 2. In this test, a 5kHz sinewave at (-20dB full scale) is fed as a complex I/Q signal into the soundcard's line output, via the loopback cable and into its line input.
Here's the Griffin iMic (white)
and here is the UCA202.