Cross Country Wireless Low RF noise 12V power supply
Until recently we advised customers using our Active Antennas or Multicouplers to use either a linear power supply or 12V battery to reduce any RF noise on the power feed.
Due to a recent EU directive on energy efficiency most small linear power supply "wall warts" have disappeared from the market and many customers ask for an alternative.
Recently in collaboration with one of our suppliers we have looked for the most RF quiet switch mode power supply and researched ways to make it even quieter.
The power supply chosen uses an IEC male connector for mains input of 100-240V 50-60 Hz so that it's not limited to one or two local mains connector types. The mains earth or ground is also directly connected to the negative rail of the 12V output.
Measurements shows that the power supply is well regulated with 12.1V at no load and 12.0V at 2A maximum load. The ripple on the output is a maximum of 2mV at full load and the ripple is well smoothed so is RF quiet.
We modify the power supplies by adding two TDK ferrite clamps at either end of the DC power cable to reduce any RF noise coming from the power supply and mains ground. Having ferrite clamps at either end also reduces any RF picked up on the cable feeding into either the power supply or the powered equipment. This is often a problem in areas with high RF fields present.
The simple external modification with ferrite clamps does not affect the FCC, UL, GS and CE certification of the original power supply.
This power supply is also useful for powering other radio equipment that needs a RF quiet 12V DC supply.
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