[Elecraft] [K3S] WSPR "Receiver Noise Level"

[Fred Jensen]

On 11/27/2016 1:30 PM, MaverickNH wrote:

> A couple of questions:
>
> 1. "...when no signals are present."  Would this be suggesting that I tune
> my K3S to a frequency off the WSPR TX range where I see no other signals on
> my P3?

In general, yes, but stay close.  Depending on the band, it may not be a 
problem, but on the lower frequencies, the ubiquitous SMPS that surround 
us all can put "noise bumps" in the spectrum.  They're very apparent on 
a panadapter and you wouldn't want to set your no-signal level on one of 
those.
>
> 2. "Use the receiver gain controls and/or the computer’s audio mixer
> controls..." Which is preferable for a K3S, adjusting the K3S gain or the PC
> Windows 10 Mixer?

In general, things always seem to work best for me if the various gain 
controls are in the middle of their ranges.  For digital modes, I 
usually set the Win mixer mid-scale and see where the K3 gain needs to 
be.  It's pretty obvious if the input level is too hot or too low for 
the K3.  If they're all right near the bottom, you may want to put a 
10:1 voltage divider in the circuit.

AGC-off is a mixed bag.  In very narrow bandwidths where the likelihood 
of another signal showing up is low, OFF and manual control of RF GAIN 
can help get a dB or two additional SNR.  However, in wider BW where a 
very strong signal can show up as you work for a very weak one, you 
could be very surprised ... and temporarily deaf.  The K3 has an AF LIM 
in the CONFIG menu.  It was put there as a safety for your hearing in 
AGC OFF situations.

When I was trying out JT-<mumble>, I left AGC on.  I've given it up now, 
it seemed like watching the barbed wire fence rust, but for many its a 
really great mode.

73,

Fred K6DGW
Sparks NV USA
Washoe County DM09dn