Late in 2016, news outlets began reporting on
American and Canadian diplomats stationed at their respective embassies in Cuba complaining
of dizziness, nausea, headaches, ringing in the ears, and other seemingly sound-related
illnesses (click on timeline at right). Similar reports have come out of China as well.
At the time, doctors and scientists investigating the phenomenon thought maybe some sort
of weaponized sonic beam was being directed at the personnel. Certain people were affected
while others nearby experienced no such phenomena, leading researchers to believe that
the presumably sonic beams were highly concentrated and directional. Some of the targeted
diagnosed as having suffered mild traumatic brain injury with likely
damage to the central nervous system.
Now, headlines are saying that the "sounds" might not have been sonic in nature at
all, but could have been caused by microwaves*. I almost
couldn't believe it when I read, "In particular, a growing number of analysts cite an
eerie phenomenon known as the
Frey effect, named after Allan H. Frey, an American scientist. Long
ago, he found that microwaves can trick the brain into perceiving what seem to be ordinary
sounds." "Zounds," I said to myself, that is exactly what happened to the NCO who was
assigned as my trainer in the U.S. Air Force at Robins AFB, Georgia, in the early 1980s.
I have told the story many times over the years, but here it is again now that it is
very timely and relevant.
After completing Air Traffic Control Radar Repairman (AFSC
303x1) technical school at Keesler AFB, Mississippi, in the fall of 1979, I headed
to Robins AFB as my permanent duty station. The next phase of learning about the equipment
was OJT (on-the-job- training). OJT consisted of a combination of hands-on instruction
by an experienced radar technician (called a "trainer"), and a self-study curriculum
of printed course material known as Career Development Courses (CDC's). CDC's were tailored
to the specific type of equipment on which you would be working as well as containing
Along with troubleshooting and repairing problems with the S-band airport surveillance
radar (ASR, aka "search"), the X-band precision approach radar (PAR),
rapcon (radar approach control) equipment,
IFF synthetic radar, VHF and UHF radios, video mappers, and other systems, we were
responsible for performing periodic maintenance and alignment procedures to keep everything
running per specifications. One of those tasks was verifying that the
polarization mechanism (used to mitigate rain echoes) in the search radar antenna
feedhorn was functioning properly. Doing so involved climbing onto the roof of the radar
trailer and removing the weatherproof cover at the end of the feedhorn to measure the
positions of the polarizer.
As you might expect, there are safety switches provided to help prevent personnel
from being swept off the roof if someone didn't know anyone was up there and, wondering
why the antenna wasn't turning, flipped the switch to get it going. A safety kill switch
for the antenna was located on the outside of the trailer at the top of the ladder used
to access the roof. As my trainer and I ascended the ladder, he explained the switch's
purpose and admonished me to always remember to place the switch in the "OFF" position
prior to climbing on the roof, which he did. He was a by-the-book guy who took his responsibilities
seriously. I duly noted the advice. We set our bag of tools near the antenna and dutifully
opened the alignment manual to the circular polarizer section. The next step of my learning
about radars was about to begin.
Sgt. Trainer, who was experienced and quite adept at this radar maintenance thing
(and a very nice guy), proceeded to demonstrate the proper procedure for removing the
feedhorn cover. That went well. Next, after a short verbal tutorial on how the polarizer
worked and what he was about to do, he moved his face in front of the feedhorn to see
inside, then very quickly jumped back out of the way. "Whoa, did you hear that?," he
asked me. "Hear what?" I responded. "That loud noise," said he. After recovering from
the surprise, he began work again. Once more he snapped his head away from in front of
the feedhorn. "Yow, there it is again," he remarked in an obviously shaken voice. After
composing himself, he climbed back down the access ladder and went into the equipment
trailer and discovered that the high voltage to the transmitter was turned on, even though
a warning sign had been placed near the emergency shutoff switch on the transmitter rack.
There was no physical lockout mechanism, and evidently "we" neglected to actually turn
the HV off, since nobody entered the trailer while we were working on the antenna. The
poor guy worried for a long time whether he would eventually develop brain cancer from
it. 750 kW peak, 0.7 μs wide, at a 1100 pps rate is a lot of noggin fry time
even for less than a second. I learned a valuable lesson that day, having to this day never "heard" microwaves in my lifetime.
In retrospect, that episode, evidently, was an example of the "Frey effect" which,
according to the paper linked to above, was first identified in 1961.
* See New York Times article, "Microwave Weapons Are Prime Suspect in Ills of U.S. Embassy Workers,"
dated September 2, 2018.
--- I would like to get ahold of the MPN-13 or MPN-14 radar system technical
orders (TO's) with schematics and/or periodic maintenance in order to scan and post
some of the pages. If you are able to provide copies of even a few of the pages -
especially the transmitter and receiver circuit schematics, please contact me at
kirtrfc (@) aol (.) com.
Posted September 4, 2018
A huge collection of my 'Factoids' can be accessed from my 'Kirt's Cogitations'
table of contents.
Topical Smorgasbord, another manifestation of Factoids,
are be found on these pages:
| 2 |
4 | 5
| 6 | 7
| 8 | 9
| 10 |
11 | 12 |
13 | 14
| 15 |
16 | 17 |
18 | 19
| 20 |
21 | 22
| 23 |
24 | 25 |
26 | 27
| 28 |
29 | 30 |
31 | 32
| 33 |
34 | 35 |
All pertain to topics that are related to the general engineering and science theme
of RF Cafe.