[BC] RF injuries

[John Lyles]

My family's physician had a diathermy machine when he retired, and gave it to me. It runs at ~13 -17 MHz, free wanderer. It was a pushpull circuit, and it had no ground on it. He told me that he quit using it in many years before (probably in the 40-50's) when a patient died from overheating, being treated for the clap. Their fever kept rising after the machine was switched off. 

Its in my living room, class 1930s art deco styling wood box. Whenever it gets lit up, shortwave reception (and up through FM) gets hammered within a few miles. 

I used to demo it with a wet sponge between the plates. In 15 minutes it would be dry again. And the flourescent light trick. 

Speaking of which, when I started out working in broadcast equipment at Delta Electronics in Alexandria, Charlie Wright had me testing some 300 or 600 ohm open wire line switches for RFE or VOA. We had a 10 kW TMC transmitter in the lab, and developed a high voltage at the insulation with a quarter wave resonator, then a high current with a phase shift and the same. Charlie was a clever engineer. This was in the 1970s. He took off one afternoon for his golf game and left me testing the thing, with that transmitter humming along at 13.56 MHz. First thing odd, I noted that my ankles were quite warm. Just ankles. I was in the capacitive field and the current was, of course, flowing through my torso to the re-bar under the floor, through the capacitance of my sneakers. Needless to say, we almost lost the custodian who was cleaning the lab, when he looked at me holding an 8 foot flourescent tube lit in my hand. He ran out saying all sort of religious things. I guess he didn't und!
 erstand
RF. 

> Keep this in mind, the woman in charge of the original testing at EPA  
> used to arrive at the lab in the morning, walk to the diathermy  
> chamber, open the door (to open the interlocks), turn on 10 kW of RF,  
> enter the chamber and close the door.  This closed the interlocks and  
> turned on the RF.  Once she warmed up, she would open the door  
> (opening the interlocks), turn off the transmitter, and remove her  
> hat, scarf and coat. She would begin her day.> 

....

Good advice. The early tests done with rabbits sitting in front of waveguides proved that cataracts were easy to acquire from microwave heating that way. 

> Bottom line:  Don't look into any high power feed horn.  THAT can be  
> bad for your eyes.  Also, if you are actively trying to become a  
> daddy, don't heat your nuts.  On American Airlines (First Class) warm  
> nuts are good, but if you are trying to be a daddy.... not so much.   
> On the other hand, if your woman and you are at odds on the subject...
> 

Having worked in high power RF industry for all of my career, I have had plenty of experience trying to help people understand nonionizing fields compared to ionizing radiation. Here at the particle factory, we got both in large quantities. We keep it all enclosed, and don't have humans in there when its on.... With each amplifier delivering about 300 kW of average power at 200 MHz, that is lot of power density at the worst frequency. The human body is approx wavelength dimensions. 

....
> 
> This RF fear really makes me angry.  Read the studies.  Get over it.   
> Unless it is ionizing, it isn't bad.

There are pages and pages of studies on this - my bookshelf on the subject is completely packed over the years of collecting and reading them. Most studies are conclusive that the main concern is heating effects. There are some which do elude to inter-cellular effects, when they did things like put chicken embryos in a high field. However, those are hard to correlate to human experience. But they are not talking about 1 MHz, but much higher like 900 MHz and up, due to the fact that nearly everyone has a transmitter beside their brain at one time or another. 

Some good references that condense stuff to a single book are:

Biological Effects of Electromagnetic Radiation
IEEE reprint series from IEEE Committee on Man and Radiation
John Osepchuk (Raytheon), ed. , 1983

Radio Frequency and ELF Electromagnetic Energies - A Handbook for Health Professionals
R. T. Hitchcock, R. M. Patterson
Van Nostrand Reinhold Publishers, 1995

IEEE Standard C95.1 1998
Read the whole thing!

And of course the stuff by R. Tell on broadcast measurement methodologies