Tell us something we don’t know.

[ponytug]

I've worked with a couple of folks who were customers of folks like @WinterDeere and I have always thought that it was money well spent. A specialized way to evaporate food material that benefited from some extra RF heat during the evaporation, where the RF created enough heat to overcome the cooling of the evaporation, without overheating the food material comes to mind. Basically, if other methods of applying heat were used, there were significant drawbacks, reduced cleanliness, burning of the food, altered taste profile, etc.

Then again I have this vivid memory of the first time that I saw a 500kW klystron up close. (It was off!!)

My experience is that very, very few folks understand high frequency RF. (I'm not one of them, either!)

All the best,

Peter

 

[kenmbz]

Our traveling wave tubes were about $10,000 apiece.
The radar back in the late 80's was about $10,000,000 before installation.
Yes government was the requestor.
We had to buy some really expensive wave guides to go from system, out to tower and 65' up in the air. Could not buy the cheaper ($400/foot) stuff, too much loss.

I had one of the antenna guys give me a "basic" antenna design book.
Talk about hard to read....

 

[Fuddyduddy1952]

Microwaves are used to cook people, too. Both intentionally, and accidentally.

On the intentional end is the Active Denial System, dreamed up by the evil scientists at one of my prior employers. Basically, a 100 kW transmitter operating at 95 GHz through a highly-directed antenna array, it will burn skin at distances of almost a half mile. The high frequency was chosen for the opposite reason of the microwave oven, as it will excite water molecules only on the surface of the skin, without causing internal organ damage.

Active Denial System - Wikipedia

en.wikipedia.org

For those who don't already know, the first resonant frequency of the water molecule is a little above 22 GHz, and microwave ovens operate down at 2.45 GHz, for better penetration. The ADS system uses 95 GHz for precisely the opposite reason, very fast decay of the signal as it propagates through your skin.

On the accidental end, a man was killed at a military base in the UK, by one of my customers operating an outdoor electromagnetic compatibility test site. Without going into the details, a man found himself out on the test range while someone was operating one of our large amplifiers (10's of kilowatts constant power), which succeeded in cooking is liver, gonads, and pretty much every other high-density organ, to some degree. He died a day or two later.

In another incident, my mentor as a young engineer managed to cook his arm while resting it on something called a slotted line, used for testing the source/load match between an RF or microwave amplifier and the load. He had his arm resting on the line, covering the "slot", and kept smelling chicken. All the while, he's thinking to himself, "who the hell is cooking chicken in the lab?" Much damage was done, before he realized the chicken he was smelling was actually the muscle in his arm being cooked from the inside out. He claims he never felt a thing, but you can just imagine how bad the burns were, if he was smelling himself cook!

Interesting stuff, I didn't hit "like", it's so terrible. In the 70s when microwave ovens became popular here I worked for a large appliance store, electronic repair technician.
Appliance repairmen didn't know how to work on them so I did. The first ones didn't have safety features like the newer ones did.
I heard about a cook who removed door so he could cook faster and soon died.
Resonant frequency is very interesting.
Back then lots of microwave ovens were returned from people cooking a potato wrapped in foil!

 

[WinterDeere]

Our traveling wave tubes were about $10,000 apiece.

Small world! Most of my career has revolved around replacing TWT's with solid state PA's! Never worked on TWT's myself, the voltages are too frightening.

The radar back in the late 80's was about $10,000,000 before installation.

Solid state hasn't made the up front cost any lower, in fact it's usually 2x - 3x the cost of a TWT for a given power and band. But the lifetime cost is so much lower, due to improved reliability, fault tolerance, repairability, etc. When you have a test site staff of 3 - 8 people sitting around for six months waiting on a replacement TWT, versus swapping a solid state PA module in 20 - 60 minutes time...

I had one of the antenna guys give me a "basic" antenna design book.
Talk about hard to read....

No kidding. I still remember my first undergraduate electrostatics class, when the prof said something like, "every curriculum has its make-it-or-break-it course, and congratulations... you've just entered yours." I was one of only two students who actually finished and passed that class that term. I think one or two others re-took the class and passed it the following term, and the rest of them all switched from electrophysics back to computer engineering or circuit design. I still don't work in antenna design myself, just all closed-form waveguide stuff. Those antenna guys lose their hair too young.

 

[dodge man]

I turned 16 in 1978 and started working in a restaurant and we had two microwave ovens. It was kind of a new thing at the time and whenever we microwaved something we always said nuke it. “The chili isn’t hot so hurry up and nuke a bowl of it”. I still say that today.

 

[ultrarunner]

As kids we would hike up to the top of a mountain to a microwave relay station... it had its own cable car to access it... all I remember is warning signs at this remote outpost.

I guest tele communication microwaves have been surpassed by other technology?

 

[ponytug]

As kids we would hike up to the top of a mountain to a microwave relay station... it had its own cable car to access it... all I remember is warning signs at this remote outpost.

I guest tele communication microwaves have been surpassed by other technology?

Not completely. Still good for remote area phone service relay, and for hedge fund traders engaged in "flash" bidding, but, yes, fiber optics have displaced microwave towers for many uses, though technically 5GHz WiFi/relay/network uses could be considered microwave.

Flash Boys

#1 <em>New York Times </em>Bestseller — With a new Afterword, Flash Boys, A Wall Street Revolt, Michael Lewis, 9780393351590

wwnorton.com

All the best,

Peter

 

[MossRoad]

I've seen a few microwave towers converted to cell towers, however, most of them are now abandoned around here.

 

[garry1p]

I remember when working for NASA back in the early 70's we were scheduled to interrogate a satellite somewhere around the moon. I had to go out to the dish antenna (small 28 footer) and change the polarization from right hand circular to left hand I re-positioned the wave guide came back down and found the transmitter was not in the dummy load but radiating at low power.
Had in been in high power I would have been fried. AS it were I suffered no ill effects but worried about it for several years.

 

[MAX-24-Dean]

But which came first?

(Egg of course. They've been around much longer than chickens
)

I'm glad this has finally been solved.

I always thought the chicken came first because I ate the eggs and not the chickens.