RF exposure

[AK9R]

I used to have a friend, he's passed on now, who was a transmitter engineer for a local TV station that also had a very good satellite earth station for uplink and downlink. This was before the days of video over Internet. There was a rack of microwave equipment in the main transmitter building, a large satellite dish outside (10 meters, maybe), and waveguides running through the ceiling space of the building. My friend used to heat up his lunch on the joints in the waveguide as they were just leaky enough to act like a low-power microwave oven.

 

[KevinC]

I used to have a friend, he's passed on now,

My friend used to heat up his lunch on the joints in the waveguide as they were just leaky enough to act like a low-power microwave oven.

Hmm....

 

[merlin]

Yup.... minor correction / possible point of discussion.. I'm not positive, but I think microwave ovens use magnatrons, which are traditionally pulsed.

Thanks
Joel

Actually CW in microwave ovens but use in radar are puled.

 

[merlin]

My days of tower jockey and RF engineer, I sort of have my own guide as to safe distance.
The human body will absorb RF which is converted to heat. That heat your body will dissipate and radiate into space. Below 50 Mhz your body becomes a radiator but enough power you can feel some minuscule heating in the wrist by grabbing the antenna. that may take 100 watts.
Draw your finger to the high voltage end of the antenna, you can get a good 1/4 inch arc and that will burn.
As frequency goes up your body absorbs RF. VHF 5 watts is nothing. 100 watt can burn with touch. I felt no warming 6 feet from 35 KW FM antenna but the absrobtion, close contact with the tower and a good inch of arc. I had burn spots all over my arms.
Talk microwave. My earth station had 10 watt 13 Ghz TX. Cover the feed horn with hand,
nothing there. Do that with with 1 Kw manetron like in ovens, you might cook your hand quick.
Ever wonder how a fly can survive a microwave oven ? they are too small to absorb that frequency, but a frog will explode. (NO, I didn't)
WiFi, 1200 Mhz is just too low power to do any harm at all with direct contact.
Lauri brough up cataracts. Hmm, I wonder, but those are usually from UVB exposure and other sources not related to radio. (Mayo clinic)
So when some suit decides what is safe exposure to RF, I take it with a grain of salt.

 

[merlin]

Hmm....

I've heard of heating hot dogs in front of radar on navy ships, but gees, stay away from the sonar. the power those have will cavitate the cells in your body.

 

[merlin]

I used to have a friend, he's passed on now, who was a transmitter engineer for a local TV station that also had a very good satellite earth station for uplink and downlink. This was before the days of video over Internet. There was a rack of microwave equipment in the main transmitter building, a large satellite dish outside (10 meters, maybe), and waveguides running through the ceiling space of the building. My friend used to heat up his lunch on the joints in the waveguide as they were just leaky enough to act like a low-power microwave oven.

Geez, that is some awful leaky fittings and a lot of power for uplinks.

 

[merlin]

I wonder how these are for encouraging hair growth?

HYS 25 Watt UHF HT

Ha Ha Ha,, a 25 watt talky ? Not without an amplifier.

 

[MUTNAV]

People have been wondering about "non-thermal" effects for a long time. The fact is that none of the science on non-thermal effects has ever been repeated. There isn't even a good physical theory as to how these effects are supposed to work. People who understand electronics and antenna engineering as well as medical research protocols are extremely scarce. Frankly, lots of research ends up with problems in either one place or another. This is why so few of them have results that have been confirmed in other experiments.

That said, Thermal effects are fairly well understood. It is also possible that pulse averaging may not be entirely accurate. Some materials may be thermal insulators that high energy pulses may shine through. The heat would accumulate because it doesn't dissipate fast enough. This would be an unusual situation in human tissue, but it's not impossible.

So the standards have fudge factors of 10 built in to them. I know this because I corresponded with a professor who was on the IEEE standards committee back in the early 1990s. He didn't think much of the notion of that fudge factor. More to the point: The exposure standard used to be 10 mW/cm^2 across the board. Then they arrived at the wavelength based standard --for "reasons." There was probably a lot of posturing and what-about-isms that often plague standards committees. Anyhow, that's where the standards we have today come from.

To summarize: Non-thermal effects of RF have not been demonstrated in a repeatable experiment. And believe me, many researchers have looked hard. Part of the problem is the use of the term "Radiation" with RF. It scares people in to thinking that if they were exposed, that their kids will turn out funny. Yet they don't hesitate to jam a cell phone right next to their heads with its half dozen radios radiating at one time or another. If RF was truly a hazard, people should have been dying all over the place when cell phones became popular.

So yes, I do my duty as ham. But I also know that these standards are based on lots of confabulation and bluster. If you're determined to find something to worry about, this should be pretty far down on your list of threats to your wellbeing.

To a point they haven't been demonstrated...

Transcranial magnetic stimulation - Mayo Clinic

www.mayoclinic.org

Seems pretty convincing.

Thanks
Joel

 

[prcguy]

I used to have a friend, he's passed on now, who was a transmitter engineer for a local TV station that also had a very good satellite earth station for uplink and downlink. This was before the days of video over Internet. There was a rack of microwave equipment in the main transmitter building, a large satellite dish outside (10 meters, maybe), and waveguides running through the ceiling space of the building. My friend used to heat up his lunch on the joints in the waveguide as they were just leaky enough to act like a low-power microwave oven.

I’ve had to check lots of waveguide junctions for leakage and one particularly bad one would burn your finger if you grabbed the flange. This was several hundred watts at Ku band. Otherwise you would never want to run with any kind of measurable leak.

 

[nd5y]

Ha Ha Ha,, a 25 watt talky ? Not without an amplifier.

It's probably a clone of this one.

Review 25W Leixen NOTE - Miklor

Review 25W Leixen NOTE - Miklor

www.miklor.com

25W PA and a fan.

 

[mmckenna]

To a point they haven't been demonstrated...

Transcranial magnetic stimulation - Mayo Clinic

www.mayoclinic.org

Seems pretty convincing.

Thanks
Joel

I have a coworker who's husband had that treatment. It did work. Apparently a strong localized magnetic field. Not sure how well that compares with a strong RF field, but would be an interesting study.

 

[merlin]

It's probably a clone of this one.

Review 25W Leixen NOTE - Miklor

Review 25W Leixen NOTE - Miklor

www.miklor.com

25W PA and a fan.

Not that they can't do it but there is not enough heat sinking so it will smoke in short order.
Even 25 watt in, the current draw at the battery would max out the ampre hour rating.
The 8 watt Baofeng on a bird watt meter tops out at 4.5 watt VHF, 3.8 watt UHF.
And they get hot after 30 second key down.

 

[merlin]

I have a coworker who's husband had that treatment. It did work. Apparently a strong localized magnetic field. Not sure how well that compares with a strong RF field, but would be an interesting study.

Probably not unlike MRI, but look how strong the field is.

 

[MUTNAV]

I have a coworker who's husband had that treatment. It did work. Apparently a strong localized magnetic field. Not sure how well that compares with a strong RF field, but would be an interesting study.

Yes, I haven't found the pulse widths though, it could be RF, my point is that it would count as a non thermal effect... Looking at the possible side effects, they sound a lot like Havana syndrome (it's probably just a coincidence though, I'm sure that the government did the research and as soon as they find out what Havana syndrome was caused by, they would tell everyone the details).

Thanks
Joel

 

[MUTNAV]

Probably not unlike MRI, but look how strong the field is.

I haven't seen it anywhere, but when it first came out, I remember that it was originally explored because doctors and patients reported decresed mental illness symptoms after having an MRI.

Thanks
Joel

 

[prcguy]

Yes, I haven't found the pulse widths though, it could be RF, my point is that it would count as a non thermal effect... Looking at the possible side effects, they sound a lot like Havana syndrome (it's probably just a coincidence though, I'm sure that the government did the research and as soon as they find out what Havana syndrome was caused by, they would tell everyone the details).

Thanks
Joel

I believe Havana syndrome was caused by high power pulsed mm wave RF aimed at a passive but reflective object in the building which picked up acoustical energy and reflected it back to a receiver that extracted audio from the Doppler effect of the passive reflective object vibrating from acoustic energy (secret conversations). The bad effects on humans were an unintended consequence of the operation.

 

[MUTNAV]

I believe Havana syndrome was caused by high power pulsed mm wave RF aimed at a passive but reflective object in the building which picked up acoustical energy and reflected it back to a receiver that extracted audio from the Doppler effect of the passive reflective object vibrating from acoustic energy (secret conversations). The bad effects on humans were an unintended consequence of the operation.

Although what you said sounds like kaplooey... It actually seems about right.

When in high school in the civil air patrol, one of the people in charge brought in a flashlight that he hooked to (what I assume) was a carbon microphone (to modulate the beam) and pointed the light at the ceiling, he then used a solar cell hooked up to an audio amp to show how it was possible to demodulate it.... Later in life I learned / figured out, that a laser pointed at a remote window would reflect light that was also modulated (of course other reasons for the window to move slightly (like sound from the outside)) was also modulated onto the laser light.

What you described was the same thing, except using radio waves.

I did have to giggle a little about the "unintended consequences" of the operation, which could be reworded as a "side effect" from a medical procedure (like TMS).

Are we getting back to at least thinking of the possibility of non-thermal effects of RF

Can you imagine the disaster it would be if technical details of such a system, if it existed. were to get out?

Now anyone thats read all of this will have to dress as trees and take weaving paths wherever they go.


Thanks
Joel

 

[Lauri-CoyoteFrostbite]

Back before all the high security stuff shut these things down, my lab used to have Open Houses, especially around Armed Forces Day.
One of the demonstration that really attracted attentions were what we did with the microwave transmitters--- like cooking hot dogs in front of C-Band horns.
Surprisingly, when these were offered to the visitors there was a reluctance to accept them--- they couldn't quite grasp that what they were seeing was just a demo of what they have in their own microwave ovens at home.

"Aren't those hot dogs radioactive now ?"

The kids, however, chowed down on the free lunch-- (mustard, ketchup, buns --provided -- your tax dollars at work )



Lauri

 

[MUTNAV]

Back before all the high security stuff shut these things down, my lab used to have Open Houses, especially around Armed Forces Day.
One of the demonstration that really attracted attentions were what we did with the microwave transmitters--- like cooking hot dogs in front of C-Band horns.
Surprisingly, when these were offered to the visitors there was a reluctance to accept them--- they couldn't quite grasp that what they were seeing was just a demo of what they have in their own microwave ovens at home.

"Aren't those hot dogs radioactive now ?"

The kids, however, chowed down on the free lunch-- (mustard, ketchup, buns --provided -- your tax dollars at work )

View attachment 143062

Lauri

If they can get one or a few kids to get into science in a big way, then it's worth every tax dollar.


All you need is one or two kids to ask how it happened, why? let them go down into a rabbit hole of info (like a real Montesori <SP> school. Then with parents that pretend to be impressed with all of the cool things they find out (even if the parents knew about it already) they'll be on the road.

Thanks
Joel




Thanks
Joel

 

[prcguy]

I believe Havana syndrome was caused by high power pulsed mm wave RF aimed at a passive but reflective object in the building which picked up acoustical energy and reflected it back to a receiver that extracted audio from the Doppler effect of the passive reflective object vibrating from acoustic energy (secret conversations). The bad effects on humans were an unintended consequence of the operatio

Although what you said sounds like kaplooey... It actually seems about right.

When in high school in the civil air patrol, one of the people in charge brought in a flashlight that he hooked to (what I assume) was a carbon microphone (to modulate the beam) and pointed the light at the ceiling, he then used a solar cell hooked up to an audio amp to show how it was possible to demodulate it.... Later in life I learned / figured out, that a laser pointed at a remote window would reflect light that was also modulated (of course other reasons for the window to move slightly (like sound from the outside)) was also modulated onto the laser light.

What you described was the same thing, except using radio waves.

I did have to giggle a little about the "unintended consequences" of the operation, which could be reworded as a "side effect" from a medical procedure (like TMS).

Are we getting back to at least thinking of the possibility of non-thermal effects of RF

Can you imagine the disaster it would be if technical details of such a system, if it existed. were to get out?

Now anyone thats read all of this will have to dress as trees and take weaving paths wherever they go.


Thanks
Joel

What I described exists and I’ve had my hands on one. Many years ago a crude version was used against a U.S. embassy and I believe employees were made sick from the high levels of RF pointed at the building needed to make it work. The version I saw was low power and would not harm anyone but could selectively “listen” into different areas or rooms from a distance.