Samlexpower SEC-1212 Owner's Manual page 10

4. The receiver may "hear" the power supply. A slowly moving, slightly
buzzing carrier heard in the receiver may be caused by the antenna being
too close. As with the transmitter related noise pick up, a loose coaxial
connector or a broken or a missing ground may aggravate this problem.
Normally these noises will be below the background or "band" noise.
Increase the separation between the power supply and the receiving
antenna. Use an outdoor antenna. This will reduce the amount of signal
picked up from the power supply and also increase the amount of the
desired signal.
5. The conducted and radiated noises are limited as per the appli-
cable national / international standards. In North America, the applicable
standard is as per FCC Part 15(B) for Class "B" digital devices. The
European standard is as per EN55022, Class "B" & EN610000-3-2, 3.
Thus, the RF interference is limited but not entirely eliminated.
6. The conducted RF noise from these power supplies is limited to
the maximum allowable levels by internal filtration. The filtered RF noise
currents ( normally < 5mA ) are bypassed to the chassis of the power
supply. The chassis is, in turn, connected to the earth ground pin of the AC
input power cord (for Class 1 units). Thus, the filtered noise currents are
intentionally leaked to the earth ground. This is termed as the "Earth
Leakage Current". For safety against electric shock, this earth leakage
current is also required to be limited. It will be seen that these two require-
ments are conflicting.
NOTE:
In some cases, to prevent electric shock hazard due to
abnormal leakage current (like in marinas, spas, hot
tubs, wet spaces etc.), the AC outlet circuits / receptacles
in these areas are served through a GFCI ( Ground Fault
Circuit Interrupter ). This GFCI is normally set to trip when it
senses an earth leakage current > 5 mA. A single GFCI may
be serving multiple AC outlet circuits / receptacles and
therefore, will be sensing the sum of all the leakage currents
of the devices connected to these. As the switching power
supplies have intentional leakage current as explained above,
it may trip a GFCI feeding multiple AC outlet circuits / recep-
tacles. In such cases, disconnect devices connected to the
other AC outlet circuits / receptacles served by this GFCI.
9.