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[K3S] WSPR "Receiver Noise Level"

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MaverickNH

[K3S] WSPR "Receiver Noise Level"

A section from the WSJT-X 1.7rc2 manual states: "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. If necessary you can also adjust the slider next to the dB scale, but note that the overall dynamic range will be best when the displayed level is near 30 dB with the slider close to its mid-point."

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?

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?

Bret/N4SRN

NK7Z

Re: [K3S] WSPR "Receiver Noise Level"

Just a short warning, if you have a local station that is running JT
modes, (or a really loud one), and you have things turned up, and the
AGC off, you will be punished...

The dynamic range of the rig is so great, that if you are using
headphones, you will be faced with a very loud signal in your ears...

If you have not experienced this, you don't understand just how loud it
can get. Make sure you have the limiter set, under CONFIG, AF LIM.

73s and thanks,
Dave
NK7Z
http://www.nk7z.net

On 11/27/2016 01:30 PM, MaverickNH wrote:

> A section from the WSJT-X 1.7rc2 manual states: "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. If necessary you can also adjust the
> slider next to the dB scale, but note that the overall dynamic range will be
> best when the displayed level is near 30 dB with the slider close to its
> mid-point."
>
> 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?
>
> 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?
>
> Bret/N4SRN
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K3S-WSPR-Receiver-Noise-Level-tp7624289.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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k6dgw

Re: [K3S] WSPR "Receiver Noise Level"

In reply to this post by MaverickNH

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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WB4SON

Re: [K3S] WSPR "Receiver Noise Level"

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 <[hidden email]> 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
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

73, Bob, WB4SON

k6dgw

Re: [K3S] WSPR "Receiver Noise Level"

Yep, totally true. Same problem/effect as when someone uses way more
power than needed on a satellite transponder. Just be careful of your
ears. At 2.7 KHz [widest roofer I have], I never encountered a really
strong signal in the passband that I could hear, in the fairly short
time I was using JT-65. One approach from "way back in radio" is to
wear your headphones somewhat forward on your head when in these AGC-off
modes. CONFIG:AF LIM ON is also a really good idea.

73,

Fred K6DGW
- Sparks NV DM09dn

- Northern California Contest Club
- CU in the Cal QSO Party 7-8 Oct 2017
- www.cqp.org

On 11/27/2016 5:47 PM, Bob wrote:

> 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