EMF WooWoo

Barry Lennox - 28 April 2025

The last newsletter held an especially interesting topic for me; “EMF”, as I have many years of practice in this field.

What these WooWoo folk get totally wrong is EMF (Electro-motive Force) is a voltage and is not a force, but rather a measure of energy. The International SI unit for EMF is the “volt”.

What they actually get their panties in a twist over is EMR Electromagnetic radiation. In free space Electromagnetic radiation is a wave with perpendicular, in-phase electric and magnetic fields that propagate to infinity (as far as we know?) at the speed of light, “C”. Electric fields are measured in Volts/metre and magnetic in Amperes/metre. They are related in a simple case of Ohms law to each other by the impedance of free space, that is 120Pi or about 377 ohms. So, if you measure the electric field it’s trivial to calculate the magnetic field, and vice versa. The totality of EMR is often expressed as the electromagnetic power density, in Watts/metre2.

The above is the fundamental case in free space. It gets more complex in the near-field and the cluttered “real world”.

Now, he is correct that his “EMF” … EMR is everywhere. There are billions of emitters. Cell phones, Wi-Fi. TV and radio transmitters, 2 way radios, GPS, radionavigation aids, Ham Radio, the Military and just about every ship and aircraft, as well as probably a greater number of accidental emitters, and let’s include that big orange reactor in the sky (No, Not TRUMP) our Sun!

Yes, EMR is dangerous at some high levels, but probably never where average citizens can be exposed. Though if you sit out too long on a clear sunny day in January, EMR will cause skin and eye damage (It’s called sunburn).

I spent some weeks doing EMC/EMI/EMV testing on a military helo (helicopter) where testing was performed at several frequencies at power levels up to 200 volts/metre. At that level, the ANSI human exposure limit was just 5 minutes in the hour. Not a bad job, work fast for 5 mins then sit around with coffee and doughnuts to discuss problems that were revealed and potential solutions.

Now any conductor in an EMR wave will have a voltage induced in it. That’s exactly of course what an antenna does! This is trivial to prove by disconnecting and reconnecting your radio or TV antenna. So, he is correct, stray wires around the farm will have small voltages induced in them. In my early RNZAF days it was a common trick to connect a small light bulb to a wire loop and walk under the transmitter towers (emitting 1000 Watts) watching the bulb light. This is quite an extreme case, never likely to be experienced by ordinary citizens, and there are national limits on exposure levels and times.

But to get to the real point, “rocks will neutralise” the “EMF”!? It is a trivial matter to show this as 100% BS. Simply connect an antenna to a measuring receiver or spectrum analyser and then attach rocks, as many as you like, and observe the difference in measured field strength. That’s right, it’s ZERO.

Almost an aside, but being a farmer, it’s interesting that he does not mention the rather special case of electric fences, where any attempt to neutralise the EMF would result in a severely degraded, or non-working fence, allowing stock to happily wander off. Perhaps he has not made the connection? (pun intended)

I intend to write to this fellow and invite him to send me a sample of his best rocks, and I will measure the EMR attenuation they cause.

Either it works, and he will be New Zealand’s 4th Nobel Prize winner, or…

it does not work, and I make a complaint to the ASA.