K3 Observations Digital Modes and SSB

[Kok Chen]

On Feb 2, 2011, at 11:41 AM, Jim Brown wrote:

> An important source of IMD (and harmonic distortion) is the sound card used to generate the digital signal.  

In the case of the K3, it is definitely poor IMD from the transmitter, since my K3's transmit IMD was even worse when set to use the internal PSK-D generator.

I have tested a direct sound card -to- sound card link (no RF in between) and got better than -80 dBc IMD from cocoaModem's PSK31 interface.

Even cheap sound cards like the Griffin iMic are pretty good with IMD.  More than you can say about their second harmonic distortion, however (at least on the input side).

73
Chen, W7AY

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