RF Intensity vs Damage to Body Tissue

[WBear2GCR]

Otoh, while not RF, lithotripsy (sp?) - ultrasonic sound waves - are used to blast kidney stones into little bits inside the body. So that larger concept would seem to work on some level.

The ultrasonic work on kidney stones is purely a physical/mechanical action - completely different from any RF interaction with the human body.

Not quite so different, actually similarities in the ways that I mentioned.

The ultrasonic waves are focused (somewhat) at a point in space, the object has to be able to "receive" the energy from the waves at a high enough level of absorption to cause the calcium stones to "explode". That is a resonance in effect.

The RF method I referred to presumes that some organisms are resonant at some specific frequencies, therefore will be destroyed when the energy impinges upon them at a high enough level.

The concepts are similar, the waves used different.

I said as much... I referred to "the larger concept".

             _-_-bear

[w1vtp]

I try to not dwell on things that aren't yet a problem but it occasionally occurs to me that the whole RF exposure junk science bogey man may be the next thing antenna haters try to gin up in their agenda to have these weird looking (to me at least) zero antenna neighborhoods.  You know, the ones that have this kind of creepy look to them because they combine the look of modern homes with the 18th Century look of no antennas.

Exactly, Robert.

These junk science types are relying on the public's ignornace to differentiate between IONIZING and NON-IONIZING radiation.

BTW, X-rays are considered ionizing radiation. So Don, I am glad there were no long term effects from this exposure.

 Phil - AC0OB

Bolded emphasis mine - Al

Phil

Precisely!  I do power density calculations for a living and deal with this issue every day  HF frequencies are considered non-ionizing radiation and such considered non-carcinogenic.  Here's a link that might be helpful:

http://www.osha.gov/SLTC/radiofrequencyradiation/

A little snippet from that site:

"...Bioelectromagnetics. 2003;Suppl 6:S74-100.  Presents critiques of epidemiologic studies and experimental investigations, published mostly in peer-reviewed journals, on cancer and related effects from exposure to non-ionizing electromagnetic fields in the nominal frequency range of 3 kHz to 300 GHz of interest to Subcommittee 4 (SC4) of the International Committee on Electromagnetic Safety (ICES). The preponderance of published epidemiologic and experimental findings do not support the supposition that in vivo or in vitro exposures to such fields are carcinogenic..."

Nevertheless, There are power density limitations that are imposed on me and that's why I have to do the calculations.  Conclusion, at least for me, don't be stupid and deliberately expose oneself unnecessarily to levels higher than necessary.  See this link from ARRL:

http://www.arrl.org/news/rfsafety/exposure_regs.html

Yet another link titled "MEASUREMENTS OF ENVIRONMENTAL ELECTROMAGNETIC FIELDS AT AMATEUR RADIO STATIONS":

http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/reports/asd9601/asd9601.pdf

73 and yes,  "Switch to safety!",  Al

 

[W3SLK]

Bear said:

The ultrasonic waves are focused (somewhat) at a point in space, the object has to be able to "receive" the energy from the waves at a high enough level of absorption to cause the calcium stones to "explode". That is a resonance in effect.

Not to hijack the thread but being a former service guy with the company that invented Extracorporeal Shock Wave Lithotripsy, (Dornier Medzine Technik), The shock wave is created buy using a HV power supply (shock wave generator) into a 'spark plug' which is submerged in Deionized and degassed water. The swg produces a voltage between 18K~25K VDC. which creates a shockwave at what is called F1. The spark plug is in a brass parabola of about 65%. At F1 the shockwave is 'bounced' in the parabola and reflected at a point which is called F2. This is the place where all the waves that were initially radiated come together with a combined mechanical force of about 35000psi, (its quite a bit, but a millimeter off of F2 and you feel just a discomforting pain). By using a 3 axis table/gantry, the patient is positioned by using a dual lo-flouroscopy X-ray so that the offending kidneystone is in F2. This is what pulverizes the kidney stone, (usually made of calcium oxelate) to nothing more than grains of sand. Incidentallly the machine was originally created by the Luftwaffe in the '60's to help prevent jet aircraft from being pitted by water vapor droplets when transiting from sub-sonic to sonic speeds.

[k9qs]

Back in 1989, I was passing through Lahti, Finland, where YLE's (now dark) longwave broadcast station was located. I was fortunate enough to be walking distance from the very cool-looking T-top Marconi, strung between two self-supporting towers, about 450 feet tall. It was possible to walk right up to the chain-link fence that surrounded the transmitter building, allowing one to get to within about 40 feet of the vertical wires, connected to a feed coming through a very large glass insulator in the building. They ran (if I remember correctly) 250 kw on 254 kc, later moving to 252. The only ill effect was a memorable r.f. burn from the fence while leaning on it to steady my camera for some pictures. The site was liberally posted with warning signs for high r.f. fields, for people wearing pacemakers.

[Steve - WB3HUZ]

Ya. I didn't think it had any thing to do with resonance. Just a mechanical shock wave - like hitting it with a hammer from a distance.

Bear said:

The ultrasonic waves are focused (somewhat) at a point in space, the object has to be able to "receive" the energy from the waves at a high enough level of absorption to cause the calcium stones to "explode". That is a resonance in effect.

Not to hijack the thread but being a former service guy with the company that invented Extracorporeal Shock Wave Lithotripsy, (Dornier Medzine Technik), The shock wave is created buy using a HV power supply (shock wave generator) into a 'spark plug' which is submerged in Deionized and degassed water. The swg produces a voltage between 18K~25K VDC. which creates a shockwave at what is called F1. The spark plug is in a brass parabola of about 65%. At F1 the shockwave is 'bounced' in the parabola and reflected at a point which is called F2. This is the place where all the waves that were initially radiated come together with a combined mechanical force of about 35000psi, (its quite a bit, but a millimeter off of F2 and you feel just a discomforting pain). By using a 3 axis table/gantry, the patient is positioned by using a dual lo-flouroscopy X-ray so that the offending kidneystone is in F2. This is what pulverizes the kidney stone, (usually made of calcium oxelate) to nothing more than grains of sand. Incidentallly the machine was originally created by the Luftwaffe in the '60's to help prevent jet aircraft from being pitted by water vapor droplets when transiting from sub-sonic to sonic speeds.

[WBear2GCR]

Well, perhaps not resonance in the usual high Q sense, but one can contrast the effect with a material that is transparent to the waves, pick RF or ultrasonic... and last time I hit a rock with a hammer it seemed to make a sound... 

Well, nvm... it's not a big deal.

             _-_-bear

[W9GT]

Ya. I didn't think it had any thing to do with resonance. Just a mechanical shock wave - like hitting it with a hammer from a distance.

Bear said:

The ultrasonic waves are focused (somewhat) at a point in space, the object has to be able to "receive" the energy from the waves at a high enough level of absorption to cause the calcium stones to "explode". That is a resonance in effect.

Not to hijack the thread but being a former service guy with the company that invented Extracorporeal Shock Wave Lithotripsy, (Dornier Medzine Technik), The shock wave is created buy using a HV power supply (shock wave generator) into a 'spark plug' which is submerged in Deionized and degassed water. The swg produces a voltage between 18K~25K VDC. which creates a shockwave at what is called F1. The spark plug is in a brass parabola of about 65%. At F1 the shockwave is 'bounced' in the parabola and reflected at a point which is called F2. This is the place where all the waves that were initially radiated come together with a combined mechanical force of about 35000psi, (its quite a bit, but a millimeter off of F2 and you feel just a discomforting pain). By using a 3 axis table/gantry, the patient is positioned by using a dual lo-flouroscopy X-ray so that the offending kidneystone is in F2. This is what pulverizes the kidney stone, (usually made of calcium oxelate) to nothing more than grains of sand. Incidentallly the machine was originally created by the Luftwaffe in the '60's to help prevent jet aircraft from being pitted by water vapor droplets when transiting from sub-sonic to sonic speeds.

Not the most fun experience that I ever had, but it works!  They knock you out during the process, so not painful then, but its not real enjoyable for a couple of days following the procedure.  Those particles remaining are not necessarily as small as grains of sand!   

73,  Jack, W9GT

[W3SLK]

Jack said:

Those particles remaining are not necessarily as small as grains of sand!

So I have heard. I've been told it the closest thing a man can feel that is similar to child birth. It beats the hell out of removing kidneystones percutaneously. You only get three chances there and then the kidney is dead. 

[WU2D]

I have had to do SAR on a couple of body worn devices and have been to the labs so I have some info.

The lab that we used was in the DC area. In the case of my devices, the antenna is actually attached to the body by taping it onto the skin.

The SAR limits are as mentioned, in mW per cm squared. To measure the SAR (Specific Absorption Rate), you first must simulate the human body tissue. This is done by mixing up some goop per government recipes. At this lab they had a sink made of non-RF absorbing plastic shaped like the human upper torso.

The goop is poured in to fill the form (like you are made creepy crawlers as a kid).

Next the UUT (Unit Under Test) is place near or in my case taped on the part of the body that it will be near on the bottom outside surface of the sink.   

Next a calibrated heat probe is centered over the part of the body of interest and the probe is inserted all the way to the bottom of the sink near the device. At this close depth, a robotic scan is initiated. The probe is withdrawn slightly and the scan is repeated. After a while a calibrated 3D heat profile is printed out and you clearly see how deep the RF is causing an effect.

In my case the devices exceeded the general public safety limits slightly, but were well within the occupational and professional limits (yes uncle has two limits and the public is protected by 10X).

It took a while to get a spot in the lab because the cell phone folks had it backed up. The object with a cell phone is to be JUST in spec - that is JUST under the limits. Otherwise you would complain that your cellphone did not work!

Mike WU2D