Yes, resistors do change with aging, and higher voltages stressing them
more than in ordinary circuits.
The decline to an indicated 2800 volts is still less than 10 per cent
off the target. Considering the resistors might only be good to 5 per
cent and the meter 5 per cent at full scale, if everything went in the
same direction, I can easily see 10 per cent.
Note some electric suppliers actually supply 240 VAC, and some 220 VAC,
which is another percentage spread to account for. You would have to
know at what mains voltage the factory measured the schematic value.
The difference between 1300 watts out and 1500 watts out would not be
heard on the other end of the contact with ordinary antennas and feeders.
This brings up a good point for all: On ANY rig new to you, it is a
good idea to measure the meter readings when it is new and record them
in your logbook for reference, assuming you keep your logbooks after
they are full, as an archive of your station setups over the years.
Meters can develop stiction and inaccurate readings after years of
bouncing around in use. In fact, does the susspect meter have a zero
adjustment that has been checked lately? Some modern meters have a
concealed adjustment, rather than the front panel screw of older
meters. Some have no adjustment, and you have to replace the meter to
restore accuracy. On those, it is helpful to have a variable pot after
the voltage is dropped, to enable fine corrections of the meter as
needed over use lifetime.
-Stuart Rohre
K5KVH
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|