Microwaves can cook your steak! — Will they also fry our brains?

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5G to rely upon segment of radio frequency spectrum

What is RF? And, why should I care?

By Gordon Allison, Jr. | Technical Writer

Thus far in this series of articles, we have had an overview of radio waves causing problems for humans. In the second installment, a local woman reported on the problems that radio waves cause her and how they limit her comings and goings. Last week, we learned about some of the shenanigans of the cell phone industry that make it easier for them to do what they want without taking into consideration problems caused for humans by their installations. 

Here, the radio frequency spectrum will be examined in some detail.  Webster’s Dictionary defines radio frequency as “an electromagnetic wave frequency located between audio frequencies and infrared frequencies.” This article will give you an idea where different radio systems fall on the continuum from audio frequencies to infrared, but the frequency spectrum continues going up to include visible light, ultraviolet light, X-rays and Gamma rays.   


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There are physical limitations to dealing with radio waves. The lower the frequency, the longer the wavelength will be. Let’s now define wavelength. Using an Eastern NC example, let’s say you go to the beach and watch the ocean waves come in.  When more waves arrive on shore in a fixed time period, this new set of waves will have shorter wavelengths than the first waves.  This means the waves are arriving at a higher frequency. Frequency is inversely proportional to wavelength. The radio waves act like ocean waves in that the distance from the crest of one wave to the crest of the very next wave defines wavelength.

In addition, the vertical distance from the bottom of one trough to the top of the following crest defines the amplitude of the wave. Higher wave heights give the wave more power (higher amplitude).

Radio/Microwave antennas must be some fraction of the wavelength to transmit or receive their frequency efficiently.  Common antenna lengths are a fraction of wavelength – 1/4, 1/2, 5/8, or one full wavelength.  A radio frequency of 1,000 KHertz (lower range) yields a single wavelength 300 meters long (984 feet)!  This obviously makes a small antenna impractical.  A one gigahertz frequency (higher range), on the other hand, has a wavelength only about 30 centimeters (one foot).

I find it interesting to know for what purposes radio frequencies are used.  Let’s examine items – from low frequency to high – that we all know something about. The highest frequency that the human ear can detect is considered to be around 20 KHz.  However, at audio shows in the 1960s, my father and I both tested for a top limit of 22 Khz!   Back then, some traffic signals used ultrasonic car detectors with frequencies in the 22 KHz range to trigger the traffic light signals (instead of coils of wire buried in the pavement). That sound really bugged me!

Around 50 KHz, you find the frequency of some boat depth sounders that can read the bottom 800 feet down.  A bias frequency of around 50 kHz was used for making the magnetic tape recordings for cassette or reel-to-reel tape recorders.  Ships and aircraft used the LORAN radio navigation system in the 100 to 400 KHz band to transit the world.  The 500 KHz frequency is used for long-range marine distress and calling communications.  The AM radio broadcast band starts at 525 KHz and runs thru 1,705 KHz.

From 1,800 to 2,000 KHz (1.8 to 2.0 MHz) is the amateur (ham) radio 160-meter band. From 3,500 KHz (or 3.5 to 4.0 MHz) is the 80-meter ham radio band. At 5.0 MHz you will find station WWV, which is the call sign of the United States National Institute of Standards and Technology near Fort Collins, Colorado, that broadcasts the exact time at a frequency so tightly controlled that it can be used to calibrate frequency measurement instruments.  WWV also broadcasts on 10.0, 15.0, 20.0 and 25.0 MHz.  Some clocks that advertise they are on atomic time standards receive these reference frequencies. The 11-meter citizen’s band (CB – as in “Breaker, Breaker” and “Come on back, Good Buddy”) use frequencies around 27 MHz.

In the late ’40s and early ’50s, television sets had only black and white pictures, starting at 48 MHz.  And at that time there was indeed a Channel One!  But it was taken away from TV service and given mostly to 6-meter ham radio and some police radios. TV Channels Two to Six occupy the spectrum from 54 to 88 MHz, and commercial FM radio takes over from 88 to 108 MHz.  Many old analog FM radios could tune down below the lowest FM channel to allow you to listen to the sound of TV Channel Six.

Very High Frequency (VHF) frequencies from 108 to 117 MHz are used for airplane navigation, although some of the stations are being decommissioned as Next Gen GPS satellite air traffic control system is implemented.  Aircraft and FAA flight centers as well as airport control towers use frequencies between 118 and 132 MHz, with 121.5 MHz being the universal distress frequency.

The frequency band from 136 to 138 MHz is used by ground tracking stations and spacecraft for space travel.  Amateur radio also has the frequency band from 144 to 148 MHz.  In the 150 MHz-plus range are frequencies for boaters to communicate, the NOAA weather radio channels and other radio services.  At 174 to 220 MHz, you will find TV Channels 7 to 13.  Another ham radio band is at 220 to 225 MHz, then some military communications, and even your garage door openers.  Another ham radio band is from 430 to 450 MHz.  TV Channel 14 begins at 470 MHz and now runs to Channel 36 at 608 MHz.  Channel 37 at 608 to 614 MHz is NOT a channel to be used for TV, because astronomers convinced the FCC to leave it vacant so they could use those frequencies for radio astronomy.

What was the reason for taking TV Channels 38 through 51 away?  During an auction (that you never heard about) in April of 2017,  the government sold those frequencies (614 to 692 MHz) to the likes of AT&T, T-Mobil and others for the princely sum of $19 billion! Yes, Fans, that is billion with a capital “B”.  If you want to know the whole story, ask the editor of the County Compass, Jeff Aydelette.  If he gives me that assignment, we will disclose complete details.

The first Generation (1G) cell phones were analog.  The FCC developed a frequency band plan, specifying a hundred channels to transmit and a hundred channels to receive.  AT&T got 50 transmit and 50 receive channels at each cell site.  Verizon, Cricket, T-Mobile, Sprint and the rest divided up the remaining 50 transmit and 50 receive channels.  When AT&T was broken up into “Baby Bells,” the channels in the areas covered by each of them went to the “Baby Bells” respectively.

Up in the 1.5 GHz region, the GPS satellite navigation system operates. The 2G and 3G (second and third Generation) digital cell phone systems in the 1.9 GHz region. Microwave cooking appliances are at 2.45 GHz.  And, as you might expect, 4G and 5G systems operate at even higher frequencies using microwaves that are even smaller – that is where danger may lurk!

In Part 5 of this series, we will examine where cell phones operate and the problems they cause.


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