[Elecraft] [K3 / K3S] KIO3B NF

[Joe Subich, W4TV]

On 2015-07-04 9:44 AM, Joel Black wrote:
 > I guess my thoughts are that if the KIO3B has a comparable NF, I’ll
 > just get rid of all my external devices and further consolidate into
 > one piece of equipment.

Given the design flaws in Signalink USB, a basic TI USB CODEC which is
used by most inbuilt USB sound implementations should have a noise
floor six to ten dB lower than the Signalink.  If the "sky noise" is
set 10 to 20 dB above the noise floor of the CODEC implementation, you
should see JT65 decodes very close theoretical -24 dB 50% threshold
while JT9 decodes should be about two to three dB better (-26 dB) at
the 50% threshold.

Most Signalink units can be improved at least 6 dB by improving the
noise bypassing (decoupling) on the 5V bus within the unit, adding
proper filtering to the USB 5V input, and replacing the voltage divider
used as a reference for the CODEC and audio op-amps with a low noise
2.3 V regulator.  Signalink's transmit quality can be improved to a
significant degree by turning down the CODEC output (Windows "slider")
to prevent distortion in the CODEC and clipping in the op-amps then
use an external PTT signal.

73,

    ... Joe, W4TV