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.
--- In ultralightdx@ yahoogroups. com
, "sdwillingham" wrote:
> For comparison, my stock PL-300wt measures about 12 dB soft-mute.
> --- 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-