Part 4 here and the last part – It gets complicated, so you’ll have to think about it.
First: WHY ONLY THE HARMONICS? Harmonic frequencies are summed together with the fundamental power frequency (50 or 60Hz normally), the result is a distorted voltage and/ or current waveform, no longer the pure sine wave that originated back at the generator. So why are only the harmonic frequencies present, such as 180Hz, 240Hz, 300Hz, and so on? How does electronic equipment know to generate only those frequencies? What’s wrong with 178Hz or 316Hz? They are and they are called “interharmonics” or frequencies between the harmonic frequencies. A special category of those interharmonic frequencies are the subharmonics, which are frequencies below the fundamental frequency. These are more common, and are often the source of the voltage fluctuations that result in light flicker. Subharmonics can also be produced as the result of the interaction between harmonic and interharmonic frequencies. For example, 180Hz and 185Hz signals together would result in a 5Hz signal that falls in the subharmonic region. In adding electronic equipment to the electricity grid infrastructure they also need single-phase rectified loads that introduce pulsed waveform harmonics. If you take the fundamental (60Hz) at a factor of 1, the third harmonic (180Hz) at 0.94, fifth harmonic at 0.78, seventh at 0.58, ninth at 0.36, and so on, and combine all of those signals, you would end up with a low-frequency splurge that can only be picked up by detection equipment operating in the dBC range or by you and I. So, it’s been around for decades, it’s also known as “dirty power”, and it’s due to phase distortion and imbalance. right now, as B-PLC/ BPL rolls out the need for at least one phase positive pole’s sine wave position to be constantly known gives rise to: FREQUENCY SYNTHESIZERS TO TUNE COMMUNICATIONS SYSTEMS The requirements of modern power line communications systems and their exotic modulation formats place greater demands on the performance of (sub and) microwave frequency synthesizers. Programmed Test Sources (www.programmedtest.com) is one of the longest running suppliers of direct analog frequency synthesizers. Their highest-frequency instrument, the PTS 6400, tunes from 1 to 6400 MHz with 20 µs or better switching speed. Although its basic architecture is analog, it also incorporates a DDS to achieve phasecontinuous switching with frequency resolution as fine as 1 Hz. Output power ranges from –3 to +7 dBm with ±1 dB flatness. The PTS 6400 exhibits phase noise of –99 dBc/Hz offset 100 Hz from the carrier and –116 dBc/ Hz offset 10 kHz from the carrier, with a noise floor of –136 dBc/Hz. WHAT HAPPENS NEXT? One phase’s (positive pole) voltage is exactly where “they” want it and the communication carrier wave can be injected at the, now known, zero voltage point. However, power supply circuitry in the above electronic units only conduct current during a period near the peak of the voltage waveform. The width of the pulse is dependent on how much current that the load needs. The more current required, the wider the pulse; the less current, the narrower the pulse. Summary: VERY FAST frequency tuner algorithms can pick up the resulting subharmonics. They are approx. 64, 90, 114, 198, 215, and 316Hz which last for only milliseconds (i.e. NOT long enough for humans/animals to hear). Subtract the HARMONIC from the SUBHARMONIC and you get a low frequency sound or Hum. ISO docs quoted in “The Hum Busted – Part 3” state that as the dBC hearing range has a flat response, whatever low-frequency noise remains sounds similar to a (distant) diesel engine running and can “hit” you in the gut/chest. Unfortunately, B-PLC/BPL has a microwave frequency component that is attached to the emission on collision with the power sine wave. It is also contained in the Hum when caused by B-PLC/BPL installations. So, not only do you hear the Hum, you also get sick from a dose of microwave frequency – It’s known as Power Density – how long you can stay in an antenna’s transmission range and remain healthy. Because the power line leaks B-PLC/BPL microwave frequencies it (the power line) is now classed as a transmitting antenna by the IEEE worldwide. There, told you it was complicated. It is why “they” are so confident that NO ONE will EVER put it all together. Nice one to wrap up Tesco’s abandonment of us all – And thanks Jack – You’re a decent bloke to try and get everyone together. -- You received this message because you are subscribed to the Google Groups "Hum Sufferers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/hum-sufferers?hl=en.
