Re: 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.


--- In, "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-

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