In article ,
Reg Edwards g4fgq,regp@ZZZbtinternet,com wrote:
There may have been incorrect house wiring such that the only power
point in the bedroom, used for the transmitter, was connected, by
mistake, to the lighting circuit.
That would be my guess. Here in the US, at least, it's quite common
for a single 15- or 20-ampere circuit to be used for both wall
outlets, and lighting circuits, in one or more rooms. There's nothing
in the electrical code which requires separation of these sorts of
loads... and in fact I seem to recall a clause which actually forbids
"one outlet per circuit" branches, for some reason.
But even then, the lighting circuit
should have been capable of withstanding the load of the transmitter
without much of a voltage drop.
It doesn't take all that much of a drop in voltage to result in a
visible change in the brightness of an incandescent-filament light.
According to one site I've found, light output is roughly proportional
to the voltage raised to a power between 3.1 and 3.4. A 5% drop in
voltage would thus result in a decrease in light level of more than
15%, which would be pretty easy to notice.
If you were transmitting 100 watts CW key-down, I'd guess that your
transmitter was probably drawing at least 300 watts from the
mains, and perhaps rather more depending on its design.
Add a few more likely or possible elements e.g. a linear power supply
which tends to draw most of its current from the mains during the
voltage peaks (and thus causes a disproportionate amount of voltage
sag on the lines during those peaks), insufficiently-thick house
wiring in the walls, and perhaps a slightly loose or corroded
connection to one of the outlets or switches or breakers, and I can
well believe that keying a 100-watt CW transmitter could cause enough
voltage drop to result in visible dimming of the lamp bulb.
--
Dave Platt AE6EO
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