Measuring PL-380 Soft-Mute


Gary DeBock
 

Hi Scott,
 
Thanks for the description.
 
Off-tuning 1 kHz up or down from a DX station's frequency is a standard TP-DXing trick to get farther away from irritating domestic splatter, and the first PL-380 models showed a dramatic improvement in the ability to maintain DX signal quality while doing this off-tuning (relative to the PL-310, D96L, and other full-blown soft mute models). It's interesting to finally see actual numbers for the difference in the soft mute function.
 
73, Gary DeBock
Puyallup, WA    
 

In a message dated 1/30/2010 6:16:28 P.M. Pacific Standard Time, sdwillingham@... writes:
 


For comparison, my stock PL-300wt measures about 12 dB soft-mute.

-Scott-

--- In ultralightdx@yahoogroups.com, "sdwillingham" ...> wrote:
>
>
> Hi All,
>
> It has been debated occasionally whether the PL-380 has
> soft-mute. The short answer is: mine does (PL-380 2009.9 ver 1)
> and it's fairly easy to measure. The procedure is to tune a
> strong, steady station, measure its average audio level, then
> off-tune by 1kHz, and finally remeasure its level.
>
> To measure the average level, use a free computer recording
> program. I think many of you have Audacity and, while it's not
> my favorite, it works fine for this purpose. Here's what I did:
>
> 1) Install Audacity and launch the program.
> 2) Attach an audio cable from your PL-380 to the computer's
> mic or line input.
> 3) Turn the radio on, tune in a strong station with good
> SNR, and set the radio's volume control to 7 or 8. Also,
> set the IF filter to 6 kHz.
> 4) Back in Audacity, locate the input meter (rightmost), and
> click on meter to start monitoring the input. (Stretch the
> meter toolbar out to see the levels better.)
> 5) Next, you'll have to locate your system's recording mixer
> and adjust the recording level. I can't tell you the
> specifics, since this depends on your sound card. If you
> are using a 'mic' input, try to turn off its 'boost'
> setting. Adjust the mixer level until the average signal
> shows about -15 dB or so on the Audacity meter.
> 6) Now monitor the signal's running peak (a dark-red
> vertical line on the meter). Determine a where this peak
> sits for a particular talker's voice or song. For
> example, I'm seeing about -12 dB on my meter now.
> 7) Tune the radio off-carrier by 1kHz. Even for strong
> signals, this causes the radio to indicate and SNR of 0 dB
> which kicks-in the soft-mute function. Measure the peak
> level again. I see about -18 dB now. So my conclusion
> is that my radio has about 6 dB maximum soft-mute.
>
> The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
> soft-mute. This probably also means that the soft-mute
> threshold is 6 dB, but that is not certain. We can also
> conclude that Tecsun is setting this deliberately, since it does
> not match with the Si4734 defaults (neither firmware 2.0 or
> 4.0). Perhaps one of you with a 'new' model can test if the
> settings have been changed.
>
> -Scott-
>


sdwillingham
 

Hi All,

It has been debated occasionally whether the PL-380 has
soft-mute. The short answer is: mine does (PL-380 2009.9 ver 1)
and it's fairly easy to measure. The procedure is to tune a
strong, steady station, measure its average audio level, then
off-tune by 1kHz, and finally remeasure its level.

To measure the average level, use a free computer recording
program. I think many of you have Audacity and, while it's not
my favorite, it works fine for this purpose. Here's what I did:

1) Install Audacity and launch the program.
2) Attach an audio cable from your PL-380 to the computer's
mic or line input.
3) Turn the radio on, tune in a strong station with good
SNR, and set the radio's volume control to 7 or 8. Also,
set the IF filter to 6 kHz.
4) Back in Audacity, locate the input meter (rightmost), and
click on meter to start monitoring the input. (Stretch the
meter toolbar out to see the levels better.)
5) Next, you'll have to locate your system's recording mixer
and adjust the recording level. I can't tell you the
specifics, since this depends on your sound card. If you
are using a 'mic' input, try to turn off its 'boost'
setting. Adjust the mixer level until the average signal
shows about -15 dB or so on the Audacity meter.
6) Now monitor the signal's running peak (a dark-red
vertical line on the meter). Determine a where this peak
sits for a particular talker's voice or song. For
example, I'm seeing about -12 dB on my meter now.
7) Tune the radio off-carrier by 1kHz. Even for strong
signals, this causes the radio to indicate and SNR of 0 dB
which kicks-in the soft-mute function. Measure the peak
level again. I see about -18 dB now. So my conclusion
is that my radio has about 6 dB maximum soft-mute.

The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
soft-mute. This probably also means that the soft-mute
threshold is 6 dB, but that is not certain. We can also
conclude that Tecsun is setting this deliberately, since it does
not match with the Si4734 defaults (neither firmware 2.0 or
4.0). Perhaps one of you with a 'new' model can test if the
settings have been changed.

-Scott-


sdwillingham
 

For comparison, my stock PL-300wt measures about 12 dB soft-mute.

-Scott-

--- In ultralightdx@..., "sdwillingham" <sdwillingham@...> wrote:


Hi All,

It has been debated occasionally whether the PL-380 has
soft-mute. The short answer is: mine does (PL-380 2009.9 ver 1)
and it's fairly easy to measure. The procedure is to tune a
strong, steady station, measure its average audio level, then
off-tune by 1kHz, and finally remeasure its level.

To measure the average level, use a free computer recording
program. I think many of you have Audacity and, while it's not
my favorite, it works fine for this purpose. Here's what I did:

1) Install Audacity and launch the program.
2) Attach an audio cable from your PL-380 to the computer's
mic or line input.
3) Turn the radio on, tune in a strong station with good
SNR, and set the radio's volume control to 7 or 8. Also,
set the IF filter to 6 kHz.
4) Back in Audacity, locate the input meter (rightmost), and
click on meter to start monitoring the input. (Stretch the
meter toolbar out to see the levels better.)
5) Next, you'll have to locate your system's recording mixer
and adjust the recording level. I can't tell you the
specifics, since this depends on your sound card. If you
are using a 'mic' input, try to turn off its 'boost'
setting. Adjust the mixer level until the average signal
shows about -15 dB or so on the Audacity meter.
6) Now monitor the signal's running peak (a dark-red
vertical line on the meter). Determine a where this peak
sits for a particular talker's voice or song. For
example, I'm seeing about -12 dB on my meter now.
7) Tune the radio off-carrier by 1kHz. Even for strong
signals, this causes the radio to indicate and SNR of 0 dB
which kicks-in the soft-mute function. Measure the peak
level again. I see about -18 dB now. So my conclusion
is that my radio has about 6 dB maximum soft-mute.

The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
soft-mute. This probably also means that the soft-mute
threshold is 6 dB, but that is not certain. We can also
conclude that Tecsun is setting this deliberately, since it does
not match with the Si4734 defaults (neither firmware 2.0 or
4.0). Perhaps one of you with a 'new' model can test if the
settings have been changed.

-Scott-


Chris Knight <chris@...>
 

Thanks Scott!

That verifies what I've observed from Day 1. I purchased the PL-380
specifically because it was reported soft mute had been disabled.

Audicity is proving itself to be useful software and it's free. Can't beat
that! I highly recommend something like this for folks testing and reporting
on the functionality of these radios.

Chris Knight (N0IJK)
Fort Lupton, Colorado
http://sites.google.com/site/ftluptonulrlogs/

-----Original Message-----
From: ultralightdx@... [mailto:ultralightdx@...] On
Behalf Of sdwillingham
Sent: Saturday, January 30, 2010 7:07 PM
To: ultralightdx@...
Subject: [ultralightdx] Measuring PL-380 Soft-Mute


Hi All,

It has been debated occasionally whether the PL-380 has soft-mute. The
short answer is: mine does (PL-380 2009.9 ver 1) and it's fairly easy to
measure. The procedure is to tune a strong, steady station, measure its
average audio level, then off-tune by 1kHz, and finally remeasure its level.

To measure the average level, use a free computer recording program. I
think many of you have Audacity and, while it's not my favorite, it works
fine for this purpose. Here's what I did:

1) Install Audacity and launch the program.
2) Attach an audio cable from your PL-380 to the computer's
mic or line input.
3) Turn the radio on, tune in a strong station with good
SNR, and set the radio's volume control to 7 or 8. Also,
set the IF filter to 6 kHz.
4) Back in Audacity, locate the input meter (rightmost), and
click on meter to start monitoring the input. (Stretch the
meter toolbar out to see the levels better.)
5) Next, you'll have to locate your system's recording mixer
and adjust the recording level. I can't tell you the
specifics, since this depends on your sound card. If you
are using a 'mic' input, try to turn off its 'boost'
setting. Adjust the mixer level until the average signal
shows about -15 dB or so on the Audacity meter.
6) Now monitor the signal's running peak (a dark-red
vertical line on the meter). Determine a where this peak
sits for a particular talker's voice or song. For
example, I'm seeing about -12 dB on my meter now.
7) Tune the radio off-carrier by 1kHz. Even for strong
signals, this causes the radio to indicate and SNR of 0 dB
which kicks-in the soft-mute function. Measure the peak
level again. I see about -18 dB now. So my conclusion
is that my radio has about 6 dB maximum soft-mute.

The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB soft-mute.
This probably also means that the soft-mute threshold is 6 dB, but that is
not certain. We can also conclude that Tecsun is setting this deliberately,
since it does not match with the Si4734 defaults (neither firmware 2.0 or
4.0). Perhaps one of you with a 'new' model can test if the settings have
been changed.

-Scott-



------------------------------------

Yahoo! Groups Links


sdwillingham
 

Further info: Via my USB-equipped PL-300wt, I can read out that
its soft-mute is configured with a threshold at SNR = 6 dB and
the soft-mute slope is 2 dB/dB. This means that for each dB
that the SNR reads below 6, the volume is reduced by 2 dB. At
SNR = 0 dB, the maximum volume reduction is 12 dB.

I suspect that the PL-380 simply changes the soft-mute slope
parameter to 1 dB/dB, so it reduces the gain more gently and to
a maximum of 6 dB. I'll have to confirm that when I get around
to modifying my PL-380 with a USB interface.

-Scott-

--- In ultralightdx@..., "sdwillingham" <sdwillingham@...> wrote:


For comparison, my stock PL-300wt measures about 12 dB soft-mute.

-Scott-

--- In ultralightdx@..., "sdwillingham" <sdwillingham@> wrote:


Hi All,

It has been debated occasionally whether the PL-380 has
soft-mute. The short answer is: mine does (PL-380 2009.9 ver 1)
and it's fairly easy to measure. The procedure is to tune a
strong, steady station, measure its average audio level, then
off-tune by 1kHz, and finally remeasure its level.

To measure the average level, use a free computer recording
program. I think many of you have Audacity and, while it's not
my favorite, it works fine for this purpose. Here's what I did:

1) Install Audacity and launch the program.
2) Attach an audio cable from your PL-380 to the computer's
mic or line input.
3) Turn the radio on, tune in a strong station with good
SNR, and set the radio's volume control to 7 or 8. Also,
set the IF filter to 6 kHz.
4) Back in Audacity, locate the input meter (rightmost), and
click on meter to start monitoring the input. (Stretch the
meter toolbar out to see the levels better.)
5) Next, you'll have to locate your system's recording mixer
and adjust the recording level. I can't tell you the
specifics, since this depends on your sound card. If you
are using a 'mic' input, try to turn off its 'boost'
setting. Adjust the mixer level until the average signal
shows about -15 dB or so on the Audacity meter.
6) Now monitor the signal's running peak (a dark-red
vertical line on the meter). Determine a where this peak
sits for a particular talker's voice or song. For
example, I'm seeing about -12 dB on my meter now.
7) Tune the radio off-carrier by 1kHz. Even for strong
signals, this causes the radio to indicate and SNR of 0 dB
which kicks-in the soft-mute function. Measure the peak
level again. I see about -18 dB now. So my conclusion
is that my radio has about 6 dB maximum soft-mute.

The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
soft-mute. This probably also means that the soft-mute
threshold is 6 dB, but that is not certain. We can also
conclude that Tecsun is setting this deliberately, since it does
not match with the Si4734 defaults (neither firmware 2.0 or
4.0). Perhaps one of you with a 'new' model can test if the
settings have been changed.

-Scott-


lrdheat
 

Hi Scott
 
When you say that the volume is lowered by 6dB (or 12 dB on the 310), does that mean that the signal has been attenuated or that the volume alone is impacted? If volume only, would one recover the equivalent audio by adjusting the volume?
 
Heatwave


--- On Sun, 1/31/10, sdwillingham wrote:

From: sdwillingham Subject: [ultralightdx] Re: Measuring PL-380 Soft-Mute
To: ultralightdx@...
Date: Sunday, January 31, 2010, 1:00 AM

 
Further info: Via my USB-equipped PL-300wt, I can read out that
its soft-mute is configured with a threshold at SNR = 6 dB and
the soft-mute slope is 2 dB/dB. This means that for each dB
that the SNR reads below 6, the volume is reduced by 2 dB. At
SNR = 0 dB, the maximum volume reduction is 12 dB.

I suspect that the PL-380 simply changes the soft-mute slope
parameter to 1 dB/dB, so it reduces the gain more gently and to
a maximum of 6 dB. I'll have to confirm that when I get around
to modifying my PL-380 with a USB interface.

-Scott-

--- In ultralightdx@ yahoogroups. com, "sdwillingham" wrote:
>
>
> For comparison, my stock PL-300wt measures about 12 dB soft-mute.
>
> -Scott-
>
> --- In ultralightdx@ yahoogroups. com, "sdwillingham" wrote:
> >
> >
> > Hi All,
> >
> > It has been debated occasionally whether the PL-380 has
> > soft-mute. The short answer is: mine does (PL-380 2009.9 ver 1)
> > and it's fairly easy to measure. The procedure is to tune a
> > strong, steady station, measure its average audio level, then
> > off-tune by 1kHz, and finally remeasure its level.
> >
> > To measure the average level, use a free computer recording
> > program. I think many of you have Audacity and, while it's not
> > my favorite, it works fine for this purpose. Here's what I did:
> >
> > 1) Install Audacity and launch the program.
> > 2) Attach an audio cable from your PL-380 to the computer's
> > mic or line input.
> > 3) Turn the radio on, tune in a strong station with good
> > SNR, and set the radio's volume control to 7 or 8. Also,
> > set the IF filter to 6 kHz.
> > 4) Back in Audacity, locate the input meter (rightmost), and
> > click on meter to start monitoring the input. (Stretch the
> > meter toolbar out to see the levels better.)
> > 5) Next, you'll have to locate your system's recording mixer
> > and adjust the recording level. I can't tell you the
> > specifics, since this depends on your sound card. If you
> > are using a 'mic' input, try to turn off its 'boost'
> > setting. Adjust the mixer level until the average signal
> > shows about -15 dB or so on the Audacity meter.
> > 6) Now monitor the signal's running peak (a dark-red
> > vertical line on the meter). Determine a where this peak
> > sits for a particular talker's voice or song. For
> > example, I'm seeing about -12 dB on my meter now.
> > 7) Tune the radio off-carrier by 1kHz. Even for strong
> > signals, this causes the radio to indicate and SNR of 0 dB
> > which kicks-in the soft-mute function. Measure the peak
> > level again. I see about -18 dB now. So my conclusion
> > is that my radio has about 6 dB maximum soft-mute.
> >
> > The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
> > soft-mute. This probably also means that the soft-mute
> > threshold is 6 dB, but that is not certain. We can also
> > conclude that Tecsun is setting this deliberately, since it does
> > not match with the Si4734 defaults (neither firmware 2.0 or
> > 4.0). Perhaps one of you with a 'new' model can test if the
> > settings have been changed.
> >
> > -Scott-
> >
>



sdwillingham
 

Good question. It is just a volume change in the audio
processing. In the audio world, this would be called
'downward expansion'. (Well, not quite. Expansion would
just be based on the signal volume, whereas the soft-mute
is based on calculated SNR.)

This suggests one way to defeat the effect: just off-tune
from the carrier by 1 kHz, which engages the soft-mute.
Then turn your volume knob up by 2-clicks (PL-380) or
4-clicks (PL-300). As long as you can live with the offset
filtering, this should get rid of the pumping effect. Since
you are already dealing with low-SNR signals, this technique
should not further degrade reception.

-Scott-

--- In ultralightdx@..., Richard Berler <lrdheat@...> wrote:

Hi Scott
 
When you say that the volume is lowered by 6dB (or 12 dB on the 310), does that mean that the signal has been attenuated or that the volume alone is impacted? If volume only, would one recover the equivalent audio by adjusting the volume?
 
Heatwave

--- On Sun, 1/31/10, sdwillingham <sdwillingham@...> wrote:


From: sdwillingham <sdwillingham@...>
Subject: [ultralightdx] Re: Measuring PL-380 Soft-Mute
To: ultralightdx@...
Date: Sunday, January 31, 2010, 1:00 AM


 



Further info: Via my USB-equipped PL-300wt, I can read out that
its soft-mute is configured with a threshold at SNR = 6 dB and
the soft-mute slope is 2 dB/dB. This means that for each dB
that the SNR reads below 6, the volume is reduced by 2 dB. At
SNR = 0 dB, the maximum volume reduction is 12 dB.

I suspect that the PL-380 simply changes the soft-mute slope
parameter to 1 dB/dB, so it reduces the gain more gently and to
a maximum of 6 dB. I'll have to confirm that when I get around
to modifying my PL-380 with a USB interface.

-Scott-

--- In ultralightdx@ yahoogroups. com, "sdwillingham" <sdwillingham@ ...> wrote:


For comparison, my stock PL-300wt measures about 12 dB soft-mute.

-Scott-

--- In ultralightdx@ yahoogroups. com, "sdwillingham" <sdwillingham@ > wrote:


Hi All,

It has been debated occasionally whether the PL-380 has
soft-mute. The short answer is: mine does (PL-380 2009.9 ver 1)
and it's fairly easy to measure. The procedure is to tune a
strong, steady station, measure its average audio level, then
off-tune by 1kHz, and finally remeasure its level.

To measure the average level, use a free computer recording
program. I think many of you have Audacity and, while it's not
my favorite, it works fine for this purpose. Here's what I did:

1) Install Audacity and launch the program.
2) Attach an audio cable from your PL-380 to the computer's
mic or line input.
3) Turn the radio on, tune in a strong station with good
SNR, and set the radio's volume control to 7 or 8. Also,
set the IF filter to 6 kHz.
4) Back in Audacity, locate the input meter (rightmost), and
click on meter to start monitoring the input. (Stretch the
meter toolbar out to see the levels better.)
5) Next, you'll have to locate your system's recording mixer
and adjust the recording level. I can't tell you the
specifics, since this depends on your sound card. If you
are using a 'mic' input, try to turn off its 'boost'
setting. Adjust the mixer level until the average signal
shows about -15 dB or so on the Audacity meter.
6) Now monitor the signal's running peak (a dark-red
vertical line on the meter). Determine a where this peak
sits for a particular talker's voice or song. For
example, I'm seeing about -12 dB on my meter now.
7) Tune the radio off-carrier by 1kHz. Even for strong
signals, this causes the radio to indicate and SNR of 0 dB
which kicks-in the soft-mute function. Measure the peak
level again. I see about -18 dB now. So my conclusion
is that my radio has about 6 dB maximum soft-mute.

The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
soft-mute. This probably also means that the soft-mute
threshold is 6 dB, but that is not certain. We can also
conclude that Tecsun is setting this deliberately, since it does
not match with the Si4734 defaults (neither firmware 2.0 or
4.0). Perhaps one of you with a 'new' model can test if the
settings have been changed.

-Scott-


Tony Germanotta
 

Thanks Scott. That had been my experience with the PL-310, that the "mute" is just an drop in audio not signal, despite the SN dropping to 0 on the meter. I guess you could find a signal so weak that you run out of clicks on the volume knob, but I generally use very efficient headphones and have never had that happen. (It looks like the 310 is also a 4 clicker.) Now I won't worry when I offtune that I am somehow losing signal intelligence along with my drop in volume.  This is an amazing chip you designed, and they did an amazing job on these radios. I think I will live with the need to work my volume control rather than move to the PL-380 with its smaller, less efficient loopstick.


On Feb 2, 2010, at 6:12 PM, sdwillingham wrote:

 


Good question. It is just a volume change in the audio
processing. In the audio world, this would be called
'downward expansion'. (Well, not quite. Expansion would
just be based on the signal volume, whereas the soft-mute
is based on calculated SNR.)

This suggests one way to defeat the effect: just off-tune
from the carrier by 1 kHz, which engages the soft-mute.
Then turn your volume knob up by 2-clicks (PL-380) or
4-clicks (PL-300). As long as you can live with the offset
filtering, this should get rid of the pumping effect. Since
you are already dealing with low-SNR signals, this technique
should not further degrade reception.

-Scott-

--- In ultralightdx@yahoogroups.com, Richard Berler > wrote:
>
> Hi Scott
>  
> When you say that the volume is lowered by 6dB (or 12 dB on the 310), does that mean that the signal has been attenuated or that the volume alone is impacted? If volume only, would one recover the equivalent audio by adjusting the volume?
>  
> Heatwave
>
> --- On Sun, 1/31/10, sdwillingham ...> wrote:
>
>
> From: sdwillingham ...>
> Subject: [ultralightdx] Re: Measuring PL-380 Soft-Mute
> To: ultralightdx@yahoogroups.com
> Date: Sunday, January 31, 2010, 1:00 AM
>
>
>  
>
>
>
> Further info: Via my USB-equipped PL-300wt, I can read out that
> its soft-mute is configured with a threshold at SNR = 6 dB and
> the soft-mute slope is 2 dB/dB. This means that for each dB
> that the SNR reads below 6, the volume is reduced by 2 dB. At
> SNR = 0 dB, the maximum volume reduction is 12 dB.
>
> I suspect that the PL-380 simply changes the soft-mute slope
> parameter to 1 dB/dB, so it reduces the gain more gently and to
> a maximum of 6 dB. I'll have to confirm that when I get around
> to modifying my PL-380 with a USB interface.
>
> -Scott-
>
> --- In ultralightdx@ yahoogroups. com, "sdwillingham" wrote:
> >
> >
> > For comparison, my stock PL-300wt measures about 12 dB soft-mute.
> >
> > -Scott-
> >
> > --- In ultralightdx@ yahoogroups. com, "sdwillingham" wrote:
> > >
> > >
> > > Hi All,
> > >
> > > It has been debated occasionally whether the PL-380 has
> > > soft-mute. The short answer is: mine does (PL-380 2009.9 ver 1)
> > > and it's fairly easy to measure. The procedure is to tune a
> > > strong, steady station, measure its average audio level, then
> > > off-tune by 1kHz, and finally remeasure its level.
> > >
> > > To measure the average level, use a free computer recording
> > > program. I think many of you have Audacity and, while it's not
> > > my favorite, it works fine for this purpose. Here's what I did:
> > >
> > > 1) Install Audacity and launch the program.
> > > 2) Attach an audio cable from your PL-380 to the computer's
> > > mic or line input.
> > > 3) Turn the radio on, tune in a strong station with good
> > > SNR, and set the radio's volume control to 7 or 8. Also,
> > > set the IF filter to 6 kHz.
> > > 4) Back in Audacity, locate the input meter (rightmost), and
> > > click on meter to start monitoring the input. (Stretch the
> > > meter toolbar out to see the levels better.)
> > > 5) Next, you'll have to locate your system's recording mixer
> > > and adjust the recording level. I can't tell you the
> > > specifics, since this depends on your sound card. If you
> > > are using a 'mic' input, try to turn off its 'boost'
> > > setting. Adjust the mixer level until the average signal
> > > shows about -15 dB or so on the Audacity meter.
> > > 6) Now monitor the signal's running peak (a dark-red
> > > vertical line on the meter). Determine a where this peak
> > > sits for a particular talker's voice or song. For
> > > example, I'm seeing about -12 dB on my meter now.
> > > 7) Tune the radio off-carrier by 1kHz. Even for strong
> > > signals, this causes the radio to indicate and SNR of 0 dB
> > > which kicks-in the soft-mute function. Measure the peak
> > > level again. I see about -18 dB now. So my conclusion
> > > is that my radio has about 6 dB maximum soft-mute.
> > >
> > > The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
> > > soft-mute. This probably also means that the soft-mute
> > > threshold is 6 dB, but that is not certain. We can also
> > > conclude that Tecsun is setting this deliberately, since it does
> > > not match with the Si4734 defaults (neither firmware 2.0 or
> > > 4.0). Perhaps one of you with a 'new' model can test if the
> > > settings have been changed.
> > >
> > > -Scott-
> > >
> >
>



jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., "sdwillingham" wrote:

>
> This suggests one way to defeat the effect: just off-tune
> from the carrier by 1 kHz, which engages the soft-mute.
> Then turn your volume knob up by 2-clicks (PL-380) or
> 4-clicks (PL-300). As long as you can live with the offset
> filtering, this should get rid of the pumping effect. Since
> you are already dealing with low-SNR signals, this technique
> should not further degrade reception.

Scott,

This is true if there is only one steady signal, or at least no phase difference between multiple signals. When two signals on the same frequency are out of phase, when they cancel each other, the drop in volume is quite a bit more noticeable on the G8/PL-300wt than on the PL-380, even when tuned to the carrier frequency.

You can raise the audio floor by turning up the volume, but then the audio ceiling is increased by the same amount, so the effect is unchanged. This is what I would call pumping: the rapid periodic rise and fall of audio level caused by phase shifts, due to stations either slightly off frequency or ionospheric Doppler shift.

These effects are common on MW, especially around sunrise and sunset.  I've also observed them on SW, when ionospheric effects cause a single signal to flutter.

73,

Jim, KR1S
http://qrp.kearman.com/ 


sdwillingham
 

Jim,

My idea is to off-tune from the carrier, so the chip "thinks"
the SNR is constantly zero. Unless the chip finds another
carrier at the off-tuned frequency, this should engage
the soft-mute operation in a constant fashion. Constant
soft-mute attenuation should not exaggerate the beating of
two competing carriers.

I haven't checked this out extensively, so there might be
some other practical limitation I'm not thinking of.

-Scott-

--- In ultralightdx@..., "jim_kr1s" <jkearman@...> wrote:


--- In ultralightdx@..., "sdwillingham" <sdwillingham@>
wrote:


This suggests one way to defeat the effect: just off-tune
from the carrier by 1 kHz, which engages the soft-mute.
Then turn your volume knob up by 2-clicks (PL-380) or
4-clicks (PL-300). As long as you can live with the offset
filtering, this should get rid of the pumping effect. Since
you are already dealing with low-SNR signals, this technique
should not further degrade reception.
Scott,

This is true if there is only one steady signal, or at least no phase
difference between multiple signals. When two signals on the same
frequency are out of phase, when they cancel each other, the drop in
volume is quite a bit more noticeable on the G8/PL-300wt than on the
PL-380, even when tuned to the carrier frequency.

You can raise the audio floor by turning up the volume, but then the
audio ceiling is increased by the same amount, so the effect is
unchanged. This is what I would call pumping: the rapid periodic rise
and fall of audio level caused by phase shifts, due to stations either
slightly off frequency or ionospheric Doppler shift.

These effects are common on MW, especially around sunrise and sunset.
I've also observed them on SW, when ionospheric effects cause a single
signal to flutter.

73,

Jim, KR1S
http://qrp.kearman.com/ <http://qrp.kearman.com/>


sdwillingham
 

An update:

My PL-380 (2009.9 ver 1) now has an added USB interface. With this, I can read back the Si4734 soft-mute parameters as Tecsun has set them up. As previously measured, the software verifies that the maximum soft-mute attenuation is 6 dB. The parameters reveal some added details. The soft-mute threshold is actually 3 dB and the slope is 2 dB/dB. This means that there is no soft-mute effect at all for SNR readings of 3 or more. Below 3 dB SNR, the audio is attenuated 2 dB for every 2 dB decrease in SNR, up to a maximum of 6 dB when SNR reaches its minimum reported value of 0 dB.

-Scott-

--- In ultralightdx@..., "sdwillingham" <sdwillingham@...> wrote:

The conclusion is, PL-380 2009.9 ver 1 radios have about 6 dB
soft-mute. This probably also means that the soft-mute
threshold is 6 dB, but that is not certain. We can also
conclude that Tecsun is setting this deliberately, since it does
not match with the Si4734 defaults (neither firmware 2.0 or
4.0). Perhaps one of you with a 'new' model can test if the
settings have been changed.