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see the current audio level setting.
For your convenience there is also an automatic level adjustment. If you press the Enter
key for 5 beeps on this display, the PX50 will sample the audio for a period of time and
look at all of the peaks. Then it will adjust the audio levels for you to prevent over-
modulation.
5.08 Set Modulation Limiting (AML)
This allows you to turn the "AML" (Automatic
Modulation Limiting) feature on and off. The pur-
pose of the AML is to prevent the modulation from
reaching levels higher than the desired modulation level, but without having a sudden
change in volume levels that may be undesirable to the listener. The Enter key is used
to toggle the AML feature on and off. With AML turned on, the PX50 will constantly
monitor the modulation level at the VCO, comparing it to the modulation threshold set-
ting. The default threshold setting is 100% which represents ± 75 kHz. When turned
on, the AML menu shows the modulation threshold setting, the user volume setting (set
in either menu 5 or 6), and the actual volume level that the AML has automatically ad-
justed to.
For each time the modulation exceeds the threshold setting, the audio volume level will
be automatically lowered a small amount. Once the modulation reaches the threshold
setting it will stay near that level. After 10 seconds of not exceeding the threshold value,
the audio levels will be imperceptibly brought back up at a slow rate until the PX50 is
back at the original volume setting.
You may override the default threshold setting of 100% modulation ± 75 kHz) by using
the Right and Left arrow keys. If you want aggressive protection from over-modulating,
lower the threshold value to under 100%. If you want to exceed the 100% modulation
so that the AML is rarely active, raise the value to over 100%.
By default the AML mode should be left on at 100%. In fact the AML will never affect
your gain settings unless your levels go over 100% modulation. If you have a properly
adjusted compressor and/or limiter in front of the PX50, the AML will never activate.
However, leaving it on provides a safety net to prevent interference with other stations.
5.09 Set Frequency Display
This menu is used to program the operating fre-
quency of your radio station. There are two ways
to adjust the frequency. You can simply use the
Left/Right arrow keys to adjust the frequency lower/higher by increments of 100 kHz.
Or, you can enter the frequency exactly with the editing mode (this may save time). To
do this, first press the Enter key. Then, use the Left/Right arrow keys to choose which
digit to adjust. Then, use the Up/Down arrow keys to change that particular digit. Then
go to each digit and change as necessary. No decimal point is necessary upon entering
the frequency. To set the frequency once it has been entered in, press the Enter key
again. This display will also show you the state of the VCO and PLL. The PLL volt dis-
play shows the voltage currently used to lock the PLL. The higher the frequency, the
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