Level of K3S audio out to digital apps on Mac

[Frank O'Donnell]

Thanks to everyone for the help getting my new K3S dialed-in to work
with digital apps such as WSJT-X and FLdigi on my Mac, with the K3S
attached to the Mac by a single USB cable. Overall it's functioning very
well now, and I've been working some nice DX.

I have one question at the moment. Especially under certain band
conditions, audio level sent from the K3S to the apps seems low. With my
prior rig (Icom 7300), my primary way of dialing up and down the audio
level sent from the rig to the computer was by adjusting the RF Gain
knob, which if turned far enough (i.e. too far) would virtually always
put the WSJT-X received signal meter far into the red. With the K3S, I
gather it's normal to operate with RF Gain turned fully clockwise all of
the time. The only other adjustment I've found on the K3S is Config >
Line Out. The default appears to be 10, and even if I take it up to the
maximum of 100 it doesn't put WSJT-X into the red. (Not that operating
in the red is desirable -- since clipping will occur -- but in the past
I've found that if the rest of the band is quiet enough, WSJT-X's
ability to decode a very faint DX signal may be improved by bring the
received audio level up just to the edge of the red.) I'm much newer to
FLdigi, where the signal levels I'm seeing seem chronically low, but
that may reflect band conditions (and, I'm told by ops more experienced
with it, that tends to be the way FLdigi always looks compared to WSJT-X).

In the Mac's audio system, there are no level adjustments for the input
USB Codec, and I don't think there are relevant adjustments in either
WSJT-X or FLdigi. So my question is, are there any other settings or
adjustments to experiment with on the K3S that might give me more
flexibility on audio level sent by USB to the Mac? If not, would using a
sound card-type device rather than USB be an alternative way to have
more ability to control the level of received audio sent to the computer?

Thanks and 73,

Frank K6FOD


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[Nr4c]

I use the RF Gain to control K3S output to FT8. I think I read somewhere that you should also turn OFF AGC.

I also use RF Gain to reduce band hiss when operating. Reduces fatigue.

Sent from my iPhone
...nr4c. bill


> On May 22, 2019, at 1:14 PM, Frank O'Donnell <[hidden email]> wrote:
>
> Thanks to everyone for the help getting my new K3S dialed-in to work with digital apps such as WSJT-X and FLdigi on my Mac, with the K3S attached to the Mac by a single USB cable. Overall it's functioning very well now, and I've been working some nice DX.
>
> I have one question at the moment. Especially under certain band conditions, audio level sent from the K3S to the apps seems low. With my prior rig (Icom 7300), my primary way of dialing up and down the audio level sent from the rig to the computer was by adjusting the RF Gain knob, which if turned far enough (i.e. too far) would virtually always put the WSJT-X received signal meter far into the red. With the K3S, I gather it's normal to operate with RF Gain turned fully clockwise all of the time. The only other adjustment I've found on the K3S is Config > Line Out. The default appears to be 10, and even if I take it up to the maximum of 100 it doesn't put WSJT-X into the red. (Not that operating in the red is desirable -- since clipping will occur -- but in the past I've found that if the rest of the band is quiet enough, WSJT-X's ability to decode a very faint DX signal may be improved by bring the received audio level up just to the edge of the red.) I'm much newer to FL
 digi, where the signal levels I'm seeing seem chronically low, but that may reflect band conditions (and, I'm told by ops more experienced with it, that tends to be the way FLdigi always looks compared to WSJT-X).

>
> In the Mac's audio system, there are no level adjustments for the input USB Codec, and I don't think there are relevant adjustments in either WSJT-X or FLdigi. So my question is, are there any other settings or adjustments to experiment with on the K3S that might give me more flexibility on audio level sent by USB to the Mac? If not, would using a sound card-type device rather than USB be an alternative way to have more ability to control the level of received audio sent to the computer?
>
> Thanks and 73,
>
> Frank K6FOD
>
>
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[Bob McGraw - K4TAX]

Regarding receiver set-up implementation, it is usually best when the no
signal band noise is some 10 dB above the noise floor of the receiver.  
Per Sherwood Engineering data, the noise floor for the K3S is -135
dBm.   Thus 10 dB above that would be -125 dBm. Now since one can't
change noise floor one must use the correct amount of attenuation and RF
Gain reduction to attain the -125 dBm target for the no signal band noise.

Here's the way I handle that.   This example, the no signal band noise
is S-4 or -103 dBm.  That is determined with the Attn off and RF Gain at
max.  Then the difference between my target of -125 dBm and -103 dBm is
22 dB.  Thus I need 10 dB of attenuation and 2 S units of RF Gain
reduction.      Lets take this a bit further.  The no signal band noise,
no attenuation and RF Gain at max, is S-8 or -79 dBm.  To attain our
target of -125 dBm we need a total of 46 dB of attenuation and RF Gain
reduction.  If we choose 15 dB of attenuation then we need 5 S units of
RF Gain reduction.   To easily accomplish this, I switch the radio from
the antenna to a dummy load.  Then adjust the RF Gain until the S meter
indicates S-5 where 1 S unit is = 6 dB.  Thus with 30 dB of RF Gain
reduction the switch in 15 dB of Attenuation I have the required 46 dB
or so.

Then to the audio.  Here I adjust the Recording Gain of the Windows
mixer.  Normally this level is about -10 dB or 24% which ever you choose
to display the value.    If the signal level on the WSJT-X is above 30
dB then you should reduce the Windows mixer level a bit more to bring it
into ideal range.

There is a caution in the K3S manual regarding advancing the K3S Line
Output level which could cause distortion.  The default value is 10.

As to using AGC, on or off, from the WSJT-X help file:   "/Use the
receiver gain controls and/or the computer’s audio mixer controls to set
the background noise level (scale at lower left of main window) to
around 30 dB when no signals are present. It is usually best to turn AGC
off or reduce the RF gain control to minimize AGC action./" I find using
my method for setting the receiver gain based on band noise, and the use
of slow AGC will prevent any likely overload of the K3S audio path, the
computer audio path, or the WSJT-X software processing.

The receiver setting of gain values works quite well for other modes as
well.    But  today I hear hams say; "gotta have more gain to hear those
weak signals".   Yep, 50 years ago this was correct, but not with
today's receivers.

In looking at the Sherwood Engineering Test data 05/10/2019, the K3S has
the lowest noise floor of any others at -135 dBm, it has the best
sensitivity of any others at 0.27 uV, and it has the best 100 kHz
blocking range of any others at 150 dB.   The point being.......you have
a darn great receiver in front of you.  Now tweak its user parameters to
obtain optimum performance which it is capable of providing.

Now for those that say "well I heard........" or that "someone told
me......."  I say go research for yourself and learn the real facts.

73

Bob, K4TAX


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[alorona]

 Adding on to the RF part of the adjustment described by Mr. McGraw below, the idea described in this old post-- I still contend-- would be a very useful graphical way of making the adjustment. Not coincidentally, I wrote it in response to a similar post by Bob almost two years ago:
http://elecraft.365791.n2.nabble.com/A-very-desirable-capability-tp7633678p7633779.html 


    On Wednesday, May 22, 2019, 4:09:36 PM PDT, Bob McGraw K4TAX <[hidden email]> wrote:  
 
 Regarding receiver set-up implementation, it is usually best when the no
signal band noise is some 10 dB above the noise floor of the receiver.  

 
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