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The PX50 has an automatic VSWR fault detection capability that operates as follows. For
Power settings greater than 15 Watts, the maximum VSWR that will be allowed before a
fault is triggered is 2.0. For Power settings greater than 10 Watts but less than or equal
to 15 Watts, the VSWR fault trigger point is 5.0. For Power settings equal to or less than
10 Watts, the PX 50 will allow any VSWR and not trigger to a fault condition. These con-
ditions were designed based on the absolute amount of reflected power that the power
amp can handle before damage may occur. This also allows an antenna to be tuned or
matched with a power setting of 10 Watts or less, and the fault condition can not be
triggered. Once the tuning or matching has been performed, the power can be in-
creased to a higher desired operating point.
Once a VSWR fault has been triggered, the PX50 operates based on the settings from
menu 13 (Power Fault), and menu 14 (Power Fault Timer). These menus determine
what power level to return to after a fault, and what time, if any, to wait before returning
to the specified power level.
5.05 Temperature Display
This allows you to monitor the running tempera-
ture of both amplifier stages. The driver amp is the
0-4W exciter on the main board, and the power
amp is the 0-50W power amp. If either stage reaches a temperature of 70 degrees Cel-
sius, a Temperature fault will be triggered, and the amplifier will automatically power
down to 0 Watts to cool for a while. Power will resume once the temperature falls be-
low 60 degrees Celsius. The power level that the PX50 will return to is set in menu 13
(Power Fault).
If you experience overheating, it may mean that your ventilation fan is not running, the
vents are blocked, or the filters are clogged. Check regularly to be sure the vents are not
blocked or clogged.
5.06 Set Volume Display
The first of the adjustment displays. If controls are
not locked (as indicated by a dim display) then you
can adjust the audio levels in this menu. To
change the levels, use the Left and Right arrow keys to increase or decrease the volume
setting. Step size is in 0.5dB increments. The adjustable range is -40 dBu to +10dBu.
This will affect the overall gain of the input amplifiers and will display left and right level
meters as well as the summed audio value for both left and right signals. Note that any-
thing over the 13th solid bar is over 0dBu.
5.07 Set Modulation Display
This displays the signal levels that are being sent to
the VCO of the transmitter. This includes the pilot,
L+R audio, and any other signals added in. The
two marks on the display indicate where the 100% modulation setting is. During edit-
ing mode use the Left and Right cursor buttons to adjust the audio levels to keep the
bargraph from just touching the 100% markers. Over modulation causes breakup on a
listener's receiver, and interference with adjacent channels. Press the up arrow once to
13
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