Samlexpower SEC-1235 Owner's Manual page 16

SECTION 6
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.
6.5 ADDITIONAL GUIDELINES FOR REDUCING RF NOISE
• Use additional appropriate AC Radio Frequency Interference (RFI) Power Line Filter
rated for minimum 10A immediately before the AC input of the power supply.
Filtered, Ferrite Coated Cord Set is another choice. These cord sets, with integral
line interference filters, reduce Common and Differential Mode Interferences
over a wide frequency range. Because they are shielded, they are also effective
against radiated interferences. In addition to the built-in filter networks, the
cable conductors are coated with an RF absorbing ferrite compound. This provides
additional attenuation at high frequencies that is lacking in most regular LC filters.
The RF absorption of the ferrite-coated cable avoids resonances at high frequencies,
reducing the conducted and radiated RF noises even further.
• Use additional appropriate DC radio frequency interference (RFI) power line filter
rated for minimum 35A immediately after the DC output of the power supply.
• Twist the Positive and Negative wires from the output of the power supply to the radio.
• The DC side Positive and Negative outputs of these power supplies are isolated from
the chassis. As explained earlier, the noise currents are filtered to the chassis of the
unit and the chassis is connected to the Earth Ground through the Earth Ground Pin
of the AC power outlet receptacle. Avoid connecting (referencing) the DC Negative
output terminal of the power supply to the Earth Ground.
• Connect a ¼" wavelength of wire on the Negative terminal of the power supply.
Connect one end of the wire to the Negative terminal and leave the other end free.
The wavelength corresponds to the wavelength of the interfering frequency. (May
not be practical for long wave lengths).
[Formula: Wave length (Meters) = 300 / frequency in MHz]
6.6 COMBINED FILTERED NOISE CURRENTS FROM MULTIPLE
SMPS ON A BRANCH CIRCUIT MAY TRIP GROUND FAULT CIRUIT
INTERRUPTER (GFCI)
During malfunction or an accident, the metal chassis of a device may get energized to
unsafe voltage due to internal high voltage section coming in contact with the chassis.
If a person standing on Earth touches this energized chassis, a leakage current
proportional to the person's skin resistance will flow through the person's body to
Earth Ground. The leakage current through the body is higher when the skin contact
resistance is lower i.e. if the skin is wet or wounded. This leakage current does not
return to the power source but is dissipated in Earth Ground. A leakage current of
16 | SAMLEX AMERICA INC.
| Limiting Electro-Magnetic
Interference (EMI)