how does RF feel/taste? how about rf injury? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: July 08, 2017, 04:38:26 am
content: Has anyone had the experience of feeling or tasting RF?I generally don't like touching or licking things connected to the outlet, and I don't have a battery powered lower-voltage RF source available, but if someone does, how does it feel on the hands and taste on the tongue? Typically I worry that something connected to mains can short out and kill me, so I avoid touching anything but ground, even at low voltages/isolated.How about RF injuries (i.e. higher energy)?I kind of felt a high frequency before, being zapped by a 10kv boiler transformer at 10khz (i think?), which nearly floored me, but I wondered how the body responds to things.. from low to high frequencies.Can you still taste something in the GHZ if it does not have enough energy to cause thermal burns, like licking a 9V battery? does anyone care to lick a sweep generator?

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 08, 2017, 04:41:55 am
content: headache, sore eyes, feels like you been kicked in the balls the next day...happened to me twice

author: Muxr
author_rank: Super Contributor
timestamp: July 08, 2017, 05:01:31 am
content: Not sure if it counts, but I got burned by my RF induction soldering iron last week. Usually when you get burned by an iron it leaves a blister.. this actually hardened my skin where it touched and it hurt pretty bad for a day.I was working on a microscope and was handling the iron with my offhand and accidentally touched the hot part.

author: KJDS
author_rank: Super Contributor
timestamp: July 08, 2017, 01:10:21 pm
content: https://cirugiafacialbenidorm.com/en/the-radio-scalpel-or-radiofrequency-scalpel/up at 2GHz, then 50W will put a hole in your finger if it has nowhere else to go

author: CopperCone
author_rank: Super Contributor
timestamp: July 08, 2017, 01:41:02 pm
content: Thats interesting. I guess your neurons have a 3db point somewhere that prevents you from feeling the 'electrical'?

author: KJDS
author_rank: Super Contributor
timestamp: July 08, 2017, 04:01:55 pm
content: As I understand it, your muscles can only be twitched up to about 1kHz. Above that they don't respond. Perhaps a frogs leg and an audio gen would be a good way to experiment.

author: alm
author_rank: Super Contributor
timestamp: July 08, 2017, 04:29:50 pm
content: It is not so much the muscles I would be worried about. More internal organs. RF can take some interesting paths through the human body.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 08, 2017, 04:40:55 pm
content: Quote from: KJDS on July 08, 2017, 04:01:55 pmMount that frog leg to a Ukulele and you have and YouTube sensation.

author: G0HZU
author_rank: Super Contributor
timestamp: July 08, 2017, 05:39:48 pm
content: I've worked in RF labs all my working life and I've had quite a few minor RF burns over the years across HF/VHF/UHF. In my case, I usually get a burn from being lazy and letting the lower edge of my palm (i.e. the sensitive skin near the base of my little finger) brush against the artwork of something like a 10W power amplifier when it is producing full power.The sensation isn't the same as being burned by brushing against a hot sharp object. A hot sharp object will dish out instant 'hot' pain and cause instant reflex action against the pain. The best way to describe a mild RF burn is that it initially feels like someone squeezing the skin in sharp tweezers but it fairly rapidly builds up to something far more intense and 'burny' causing rapid withdrawal. It's a bit like getting a regular burn but spread/ramped up over maybe a second and without the 'hot' feeling and in my case it's very focussed into a fine point on the skin where the contact with the circuit is made. Sometimes it leaves a little pale dot on the skin where the contact was made.I've never had a bad RF burn up at high power from a big RF amplifier because I'm a lot more careful at high power. I'd imagine that it hurts a lot...

author: dmills
author_rank: Super Contributor
timestamp: July 08, 2017, 06:57:08 pm
content: I had a 250W @ 100MHz accident years ago, working on an output filter, got distracted by the phone and forget the PA was on line, reached in and squeezed one of the coils.Damage goes deep and takes a bloody age to heal, but you don't really feel it at the time, half an hour later however.....Regards, Dan.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 08, 2017, 09:16:29 pm
content: Quote from: CopperCone on July 08, 2017, 01:41:02 pmI think it's probably more like your flesh acts as a low pass filter.... so instead of a sharp sensation or sudden muscle contractions, you just sort of get cooked. I haven't experienced any myself, but my dad's told me stories of working on jammer pods for aircraft where their ground tests required everyone to be outside of a shielded test chamber building or inside the shielded cockpit, because it would literally only take a little bit to cook you if you were close when it was on. Energy is energy, after all.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 08, 2017, 10:48:09 pm
content: Relevant to thread,Quote from: DaJMasta on July 08, 2017, 09:16:29 pmNerve potentials roll off around 700Hz, IIRC. Below that, you feel about the same amount of shock, and above that, you feel less and less.Skin effect doesn't have much to do with it; the skin depth of flesh is still several cm at 2.45GHz. Think of this next time you're microwaving something big, like a bowl of soup, or a roast.Tim

author: CopperCone
author_rank: Super Contributor
timestamp: July 09, 2017, 06:48:05 pm
content: Quote from: G0HZU on July 08, 2017, 05:39:48 pmI have some PAs. They will really injure you at only 10 watts from a brush? At 50 ohms, this is only 22 volts right?On dry skin? That would mean its more dangerous then low frequency, in a way. I can't really feel 20V .

author: G0HZU
author_rank: Super Contributor
timestamp: July 09, 2017, 09:16:47 pm
content: QuoteI'm not sure 'injure' is the right word but it can feel a bit like being mildly stung by an insect in that the pain/shock rises like a ramp before I pull my hand away. But a regular burn from a hot object is instant. I don't think it does any harm and I only seem to get them on the sides of my hand or side of my little finger where the skin is very sensitive. It's also the part of the hand most likely to catch the PCB tracks where RF can be present.

author: CopperCone
author_rank: Super Contributor
timestamp: July 09, 2017, 09:25:43 pm
content: so skin impedance is lower at rf

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 09, 2017, 10:18:04 pm
content: "For the first millisecond, it just felt like the skin was warming up. Then it got warmer and warmer and you felt like it was on fire. ... As soon as you're away from that beam your skin returns to normal and there is no pain."I can confirm you feel heat at 2.7 GHz (pulsed source, ~700kW, 0.1% duty cycle). Feels like a sunlamp. Haven't been exposed to more than a few milliwatts at higher frequencies. We're always advised to never stare into open waveguides or antennas, since your corneascan get cookeddue to lower blood flow compared to the rest of the body.

author: JohnG
author_rank: Frequent Contributor
timestamp: July 10, 2017, 04:41:35 pm
content: Quote from: G0HZU on July 08, 2017, 05:39:48 pmAt my first real engineering job doing mobile RF PAs for Motorola, I was troubleshooting and followed already-ingrained habit of touching various circuit points to see what happened. When I touched the stamped-mica cap at the output of the matching network, I burned the S**T out of my finger. For the first half-hour or so, all I could see was a tiny dot on my fingertip, and I didn't think much of it. As the day went on, it hurt more and more, and by the end of the day there was a big, deep, dark blister that covered my entire fingertip and hurt like hell. It took weeks to heal. I think the RF made a little hole in the out layer of skin, hit the live layer, and spread out. I really think hard about circuits now, before I go sticking anything in them.The amp was an 800 MHz amp rated at 35 W. All I touched was a DC blocking cap, so I didn't get anywhere near full power.

author: dmills
author_rank: Super Contributor
timestamp: July 11, 2017, 10:05:09 am
content: Quote from: JohnG on July 10, 2017, 04:41:35 pmClassic RF burn, they do suck do they not.I suspect everyone working with proper RF power does this once.Regards, Dan.

author: CopperCone
author_rank: Super Contributor
timestamp: July 13, 2017, 07:04:24 am
content: if you made "swim goggles" out of mesh (deep mesh, structured like beehive material), using RFI gaskets instead of rubber gaskets for the 'seal' against the skin, that you could wear, would this protect your eyes from cataracts from a strong microwave source (that can plausibly cause the cornea to overheat)?This would be instead of a full hood., which still does not offer eye protection (but is commercially available!) Now, they might get hot.. but the only un-healable areas of the body for microwave exposure are eyes right?So if you were blasted with some strong microwave, you would experience burns on the face skin, heavy burns around your eyes (from metal gasket heating)... but presumably the cornea would be heavily protected?Could the interface between the RFI gasket of the goggle 'outline' and the skin be enough to protect microwave access to the eyeball surface? Or would you need to supplement with something like silver conductive paint (perhaps latex mixed with silver powder)? on your eyelids and area around the eyes? (so you look like you have tin-man makeup on...).I'm entirely serious btw..Does anyone know the mechanics of the eyelid acting as a cooling system too? If your eyes are closed.. how good is that? I;m guessing that tis heating in depth due to skin effect? So you would need an actual shield.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 13, 2017, 07:37:46 am
content: Linemen doing in-situ work have Faraday cage garments, made with something like 10% stainless fiber.That exact clothing wouldn't be ideal, but something a bit heavier in copper would do a fine job, yes.Quote from: CopperCone on July 13, 2017, 07:04:24 amWell, the testes.Or, really, any area that has poor blood flow that can be heated dangerously by ambient radiation. Or given enough radiation, any area at all.Tim

author: jpb
author_rank: Super Contributor
timestamp: July 14, 2017, 09:05:31 pm
content: Microwave ovens give a good demonstration of the effect of RF, especially at frequencies where there is strong absorbtion by H2O.As a young engineer in the 1980s working on MMICs, there was a guy in his 60s in the lab who worked on microwave/radar systems in the early days just after the war I guess and he had some slightly wild stories. At one time they tested the effect of microwaves on concrete blocks - nothing happened for a long time and then they exploded because of the built up steam pressure.I think that there was a high incidence of cataracts in radar operators in the war with the early sets that were very leaky - basically they were cooking their eyeballs but this may be just legend.There have been a few court cases over people claiming that they develop tumours as a result of excessive mobile phone usage - as it is non ionizing radiation I guess it must be down to increased temperature if the claims have any validity.We used to use an antenna consultant who kept his microwave oven in a shed - he wouldn't have it in the house because he reckoned that there were dangerous levels of leakage that would have a cumulative effect.

author: David Hess
author_rank: Super Contributor
timestamp: July 15, 2017, 04:27:06 pm
content: Less than 5 watts into a helical resonator can give you a severe burn; even 1/2 watt can burn you in this case because the coupling is so efficient. After I discovered this and tested it with a neon bulb, I decided that if I ever try to make a gas laser, I am going to use a helical resonator for excitation.5 watts or more into a dipole can be "felt" as you run your hand along the length of the dipole.

author: Harb
author_rank: Regular Contributor
timestamp: July 17, 2017, 12:18:13 pm
content: I have had some minor RF burns from time to time....sort of feels like its burning from the inside working its way out.......I did see an uplink tech jump about 10 feet in the air and come down breaking his wrist after pushing his leg up against a dummy load port on a Sat uplink TX once.......the scream almost gave me a hearing problem.

author: Sceadwian
author_rank: Unknown
timestamp: July 17, 2017, 02:12:59 pm
content: Remember with RF you have capacitive coupling as well. Physical contact isn't even needed if you're near the antenna.Quote from: CopperCone on July 09, 2017, 06:48:05 pm

author: Astrodev
author_rank: Regular Contributor
timestamp: July 17, 2017, 02:57:00 pm
content: Reading the comments reminded me of many years ago when I used to work on medical equipment and there were 2 pieces of equipment that need extra care and respect, the first was a defibrillator, essentially a high voltage cap (2-3Kv) which would self charge if you weren't careful.The was a diathermy which is relevant here as the output was at 1-3KV but unlike the defib which was DC this was running at several hundred MHz using modulation to control the type of cut, essentially you could cut through flesh like butter using a poker (this is probably an over simplification but we used cut through bars of soap using what was effectively a round piece of wire as the knife. Needless to say checking the output of these units was done with great care.

author: AF6LJ
author_rank: Unknown
timestamp: August 03, 2017, 12:20:17 am
content: Speaking from experience they hurt like hell, they call it RF Burn because it burns and while with low energy, and not accompanied by DC voltage it takes a while for the result to appear.Now if you want bleached and desiccated tissue that smokes, add a few hundred watts and a few hundred volts...Been there..Done that (not intentionally)Had the scars for twenty five years before they faded away.Oh I almost forgot.That experience was entirely painless at the time and there was so much nerve damage that except for the occasional stabling pain it itched a lot.

author: TheDane
author_rank: Regular Contributor
timestamp: August 03, 2017, 08:09:58 pm
content: Back in the 90's I was on packet - 144.675 MHz, the 10W output from my radio ran into a BNC T-splitter (my antenna cable wasn't long enough, so I used the t-splitter as a pass through with another cable on it - and everything would fit into my desk setup neatly).One day I had to move something around below my table, where the t-splitter was located. When I grabbed the connector to move it, my TNC-2c decided to send a packet - while my thumb was touching the BNC male end. My finger felt like a nail suddenly had been hammered into it. (I knew what had happened instantly, as I heard the relay click and knew it was on TX - into 50 ohm, but the cable was quite long, and RG-58 - so I wonder what impedance my finger had, and what was offloaded into the antenna)After a day or so, I had a really sore and hurtful white spot in the center of a ring - naturally fitting the end size of the BNC connector. It took a looong time to heal, and i remember at one point being able to pull out a piece of white dead flesh at the center.On a different note, I was repairing TV's at that time. One day the cable going into the high voltage transformer broke off the stud we used to insert into the transformer. (Easy insert/removal - as the standard connection is just a wire, not good for a module repair station)The end was exposed, and naturally it broke off right when I touched it - leaving my right finger in such close proximity that I could see a blue glowing halo around my fingertip. 15625 Hz, 27kV (as I remember) feels not quite fun. I could move my arm away, and did so very fast. It didn't hurt as much, but it's surely something I wouldn't recommend. (It was pure AC, as the tube was disconnected - a huge nasty capacitor that zaps - and that hurts too, I know...)Other things that hurts when fixing tv's and not being lucky touching insulated items 100% of the time:Touching the 1200V vertical line deflection yoke circuit feels like it kind of snerrs, or saws - as it is a saw tooth signal (at 50 Hz here in Europe). It stuns your arm for a while (minutes), and the few times I was so unfortunate, I was sweating tons afterwards.Touching the 300Vdc capacitor contracts muscles while the capacitor de-energizes. It is amazing how much muscles can contract, and the feeling when discharging makes you aware how your muscles react. I have never touched 300Vdc live, it was always off net - and I was stuck until the voltage was low enough to 'get away' - it might have been a mind trick, and time seemed to go very slow for an instant. Anyways, it is not recommended - and I'm happy to report that it's been a long while since I last touched something I later would rather have not.In any case - use your mind before you use your hand - something I have learned, and used since.- also having one hand in your pocket (or elsewhere, not touching ground or other conductive materials) is a super good idea.

author: bd139
author_rank: Super Contributor
timestamp: August 03, 2017, 08:30:08 pm
content: High voltage scares me!A friend had a very illegal CB PA. think it was 100W or so. We tried it on a Heath cantenna. All good. So I lean out the window to connect it to the mast and have my finger on the end and the bastard keyed the TX. I felt it, then it stopped hurting after about half a second. Shouted at him to pack it in. Climbed back in and there was a black spot on my finger. This turned into a pimple, burst and within 2 days my entire finger went purple. Cleared up in a couple of weeks. Never hurt past the first half a second.Then about a year ago I sliced the finger open with a Stanley knife which suspiciously didn't hurt even slightly. Reckon I killed off all the pain receptors 25 years ago!

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 06:16:20 am
content: damn I think I might get some protective gear from hollandsheilding!

author: vk6zgo
author_rank: Super Contributor
timestamp: August 15, 2017, 07:25:36 am
content: Quote from: bd139 on August 03, 2017, 08:30:08 pmNope!You just got older & tougher!I've noticed the same thing, & although I've had a few RF burns over the years, the loss of "sookiness" also seems to apply to places where the was no such burn.

author: bd139
author_rank: Super Contributor
timestamp: August 15, 2017, 07:38:40 am
content: Interesting point. Shame the rest of me seems to start hurting as I get olderI actually got a minor "warning shot" off my own hooky PA with a diode probe as well when I was replacing something. Must have burned myself a hundred times on hot transistors though.

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 03:26:16 pm
content: well, at least its difficult to poke yourself with an N connector.I have been getting zaps because for some reason, when you measure the voltage difference between the GFIC ground and the Earth Ground on a regular outlet, there is a 60V potential (with high Z meter)...Feels like tingling/burn when I hold two different equipment chassis.Why do I have a non GFIC ground? Because some of my equipment trips them.If I connect my hp 70000 SA to a UPS, then plug the UPS into one of the GFIC outlets, it trips.. but not the other ones. I put 5 outlets in the lab during remodeling/putting in new rockwool insulation in the walls, and they are connected to 3 separate circuit breakers, it looks like I need to have seperate breakers and GFCI for the HP70000/UPS then the rest of my equipment.... my home has a new grounding rod too so I don't know what the fuck...I am guessing there is ALOT of Y- filtering in the power strip, GFIC and the HP70000, so it trips the residential limit... the traveling wave tube amps seem to do the same thing, so I have a separate outlet and power strip for non GFIC compliant devices... but it burns... enough to lean on the fucking equipment and you get painful tingles. it's a complete mother fucker (but only if you touch a GFIC connected chassis and a non GFCI connected chassis.I almost want tog et rid of the GFCIs but I don't really trust half the shit I get on ebay.however, this situation is still alot better then some of the shit I had to deal with in my life (being soaked by a electrohydraulic device not connected to a GFIC, with exposed wiring on 2 phase (that itself runs a cooling system at 150VDC).. then having wiring explode 2 inches away from your finger. I kind of appreciate GFIC since that near miss. No isolation in that thing either. What a fucking death trap that was.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: August 15, 2017, 03:44:38 pm
content: Quote from: CopperCone on August 15, 2017, 03:26:16 pmnot trying to be pedantic, I used to say this also, but I think what you mean is "split phase" unless you were around some very specialized plant power system

author: retrolefty
author_rank: Super Contributor
timestamp: August 15, 2017, 04:45:40 pm
content: Many old Ham operators from the vacuum tube era can tell you about RF 'mic burns' on their lips caused by stray RF feedback in the shack. This started in an era where most homes didn't even have a distributed ground running between outlets. One had to install ground rod(s) learn and apply SWR rules about matching tube output to matching networks to antenna bandwidth, all in the hope to prevent those painful lips burns when holding the metal stand mounted microphone. That tended to inhibit long rag-chewing QSOs.

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 04:45:55 pm
content: Quote from: WastelandTek on August 15, 2017, 03:44:38 pmyea your right. It;s just difficult to anticipate the DC ground wire being hot with line voltage when the thing is fucking powered off. I did not want to disconnect it because of ESD damage potential, now I just use a grounding clip when I work on stuff so this never repeats itself. Fuck leaving stuff connected to mains. most places are not equipped for that kind of stuff though.... you need to typically build something... or I guess shove a banana plug into the outlet ground but thats dangerous itself. Need a conduit ground with a pip clamp.

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 04:48:47 pm
content: Quote from: retrolefty on August 15, 2017, 04:45:40 pmAre you saying that the metal bit on the microphone meant to hold the filter / foam in place turned into a stray antenna capable of emitting enough power to burn someones lips capacitively?

author: retrolefty
author_rank: Super Contributor
timestamp: August 15, 2017, 05:50:17 pm
content: Quote from: CopperCone on August 15, 2017, 04:48:47 pmI'm sayin many an old Ham operator had experienced RF lip burns, why and how is probablybeyond my abilities to completely understand other then 'RF in the shack' was real and hadmany causes and cures. Some mics of the era were all metal and wired to the common lead of the microphone element.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 15, 2017, 08:02:46 pm
content: Also, the fact that audio systems were largely tube, back then, meant little demodulation of stray RF and thus feedback within the transmitter itself (think acoustic mic-speaker feedback, but EM driven!).In short, RF going up the antenna feedline is dumb: there is no such thing as a good antenna design which has unbalanced feedline current. If the line is not grounded frequently and solidly, that current goes right up into the shack, and develops voltages on all the equipment. (The purpose of a balanced antenna is to not have to worry about grounding the feedline at all, and to ensure a consistent radiation pattern regardless of feedline orientation, length and grounding. Doesn't that sound like a good thing not to have to worry about?) If that doesn't cause malfunction already (it's a testament to the PSRR and filtering of any unit, that can survive common mode currentscapable of RF burns, without itself malfunctioning!), it can be big trouble for the operator, or other equipment (that isn't so robust).Tim

author: babysitter
author_rank: Frequent Contributor
timestamp: August 18, 2017, 10:29:31 pm
content: Had a mild 10W burn which i received (haha) during my early ham radio career.I wonder why no one yet mentioned raytheons' pacifying ADS - microwaving pain right into he upper skin layers.https://en.wikipedia.org/wiki/Active_Denial_System

author: CopperCone
author_rank: Super Contributor
timestamp: August 18, 2017, 11:34:30 pm
content: I think that is typically considered terahertz/mm waves rather then microwaves.Kind of think though, would be nice to have a MM wave detector without needing 10000$ of mixers.I also read some stuff about MM waves possibly being carcinogenic (in a unique way, despite being nonionizing)

author: WastelandTek
author_rank: Frequent Contributor
timestamp: August 19, 2017, 12:00:36 am
content: Quote from: CopperCone on August 18, 2017, 11:34:30 pmNot sure what the mechanism would be, but I will concede that we seem to have a really poor track record predicting the long term health effects of new technologies.was just reading a history of Tektronix last night...Quote

author: CopperCone
author_rank: Super Contributor
timestamp: August 19, 2017, 12:55:22 am
content: http://www.osa.org/en-us/about_osa/newsroom/news_releases/2013/intense_terahertz_pulses_cause_dna_damage_but_also/Seems to coincide with various things I read about involving light causing skin healing. Seems to be a mixed bag. Then again we can't even figure out if alcohol is good for you or not....Very interesting since hot objects produce some THZ (i.e. the glowbar is a THZ standard source (though broadband, and weak).Perhaps this is part of the reason why fireplaces/campfires are kind of therapeutic/healing, sometimes (so long you avoid smoke). I end up feeling pretty good after I have been warmed up by a (distant) hot source. Radiation heating defiantly has a different effect then convective heating on the body.

author: james_s
author_rank: Super Contributor
timestamp: February 12, 2018, 01:14:14 am
content: I'm not sure how you could taste RF but I'm not about to try.I've gotten a minor RF burn on my finger once, I had a small Tesla coil running on the table about 2 feet from my body and I reached over to turn off the light. My finger brushed the grounded screw holding the cover plate on the light switch. It felt a bit like something hot and abrasive scraping my finger, later on it felt more like a minor burn. I'd hate to see what a more severe RF burn feels like.

author: Teledog
author_rank: Regular Contributor
timestamp: February 12, 2018, 04:24:38 am
content: First RF "burn" was in class in the 80's.Testing a CB radio..had the bare coax center conductor accidentally touching my arm (on a grounded steel table) & was stupid enough to key it.Only a couple watts..no marks, but surely felt it!Second was touching a big glass diode on a 35W VHF rig, diode "felt " cool,.. until I keyed it..OW!!! Instantaneous pain!No marks on the fingertip, diode was ice cold after keying it..initially thought the diode was the problem, but it was obviously an IBM error (Idiot Behind Machine error)Stupid tricks..do not attempt!