Can some one help me understand the difference between Radio Frequency and Power Frequency. This topic is related to a previous post I made about welding and pacemakers. My problem is related to the magnetic field which arises around the power cords of a welder interferring with the operation of a pacemaker

 

Frequency is frequency.
Depending on the circuit, the electromagnetic source may propagate into the air if it can find some part of the hardware to act as an antenna.
Generally screened cable or a grounded metal casing will contain any stray EMI.
If the source frequency, or a multiple of it, (known as a harmonic) is of sufficient strength it will cause interference with devices operating at radio frequencies (RF). Traditionally capacitors & inductors have been used to reduce or eliminate such interference. AM reception on a car radio will give you a good idea of the various sources of interference in a motor vehicle.
More Info here http://en.wikipedia.org/wiki/Electromagnetic_interference

 

Power frequency is usually in the low frequency region of 25Hz to 400Hz.

Radio frequency ranges from perhaps tens of kilohertz up microwave frequencies.

 

RF = Radio Frequency, commonly found inside walkie talkies.
PF = Pie Frequency, commonly found inside microwave ovens.