> As the old saying goes, "it depends." In this case, it
depends on where
> the sound card clips/distorts, how much RF you might have
floating
> around your shack, and providing immunity to hum/buzz that
might be
> flowing on the shield of the cable between your PC and
your rig.
Hi Jim,
I wouldn't put any stock in the idea that a pad reduces
common mode buzz or RFI.
> 3% THD corresponds to the harmonics being 30 dB below the
fundamental.
> Most sound cards ought to be at least that good unless
they're at clip,
> especially if there's no load on them, and a rig is a high
impedance
> load.
A -30dB spurious would be a big problem for anyone in a
quiet location even if the desired signal power was only a
few watts!
PSK and other modes generated in soundcards and processed
through SSB transmitters really need to be placed someplace
away from weak signal work, or the spurious trash needs to
be in the microwatt power level range.
73 Tom
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