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

[Bob]

Well, everyone is different I suppose, but I believe the intent of WSJT-X
and the JT65/JT9 modes is to open your RX filter wide, to 4 KHz.  That lets
you see every JT65 AND JT9 signal in the bandpass.  If you narrow down the
filter you will miss many of the signals.

Because of the wide bandwidth, you really need to turn your AGC OFF.  This
will prevent a strong signal somewhere in the passband from suppressing the
RX gain to the point that weak signals are missed.  Turn your RF gain fully
CCW, then turn the AGC OFF.  Then advance the RX gain until you see about
"30" on the WSJT-x meter (left side - per the manual).  I drive my
interface off the line output, so the AF setting in not material.

When done this way, it is very common to decode 20 or more signals per pass
on 20 meters.  And it is fairly easy to have DXCC within a couple of weeks,
especially if you use JT-Alert too.

Good luck!

Bob, WB4SON


On Sun, Nov 27, 2016 at 6:31 PM, Fred Jensen <k6dgw at foothill.net> wrote:

> 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
>
>
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