SSB Transmit and Pacemakers

[Olorin]

Hello All,

I am installing an ICOM M802, AT140 and using my tallest Shroud as an antenna. (I'm on a catamaran and have no backstay.)

What are the safety considerations for people with pacemakers?

When we checked with the pacemaker manufacturer wrt the Radar, they said make sure the radar is five feet above your head which is the same for people without pacemakers.

thanks in advance for your help,

Ross

[roverhi]

For something as critical as a pacemaker, wouldn't even think of coming to this forum for information. We are a congenial group but much of our inpu tis personal bias, hearsay and, sometimes, downright wrong opinion, this contributor not excepted. You need to have enough experience/knowledge to filter the information and use what applies to your particular needs.

Go to the manufacturer and find out what the problems could be and how to avoid them from the people that really know the electronics. Perhaps wearing a coat of chain mail would give you a personal Faraday cage if you have concerns about the RF.

[AussieGeoff]

Originally Posted by Olorin

Hello All,

I am installing an ICOM M802, AT140 and using my tallest Shroud as an antenna. (I'm on a catamaran and have no backstay.)

What are the safety considerations for people with pacemakers?

When we checked with the pacemaker manufacturer wrt the Radar, they said make sure the radar is five feet above your head which is the same for people without pacemakers.

Aside from 'Don't touch the shroud when the radio is in use.' (Obvious)
I'd suggest keeping at least six feet away at a minimum until you get a definitive answer from the manufacturer of the pacemaker.

IIRC, an M802 is about 100w Peak Envelope Power on SSB, so the average power is quite bit higher than the radar, even though the radar is much higher powered (unless it's FMCW, which is an entirely different species of equine and unlikely to be an issue). The average power from even a 4kw radar is far lower than the 100w or so from the HF radio. If this seems not to make sense, consider that the pulse duration and pulse repetition frequency of the radar, when you run the math over it, means that the transmitter is on for only a fraction of the time it is in receive (ie not transmitting) so the AVERAGE power, which is what we are concerned about, is well below the average power of the HF radio, even though it's a much higher powered pulse, it's very short duration. Further, the radar beam is quite narrow at 3cm so if it's pointing even a relatively small number of degrees away from you, you are not receiving enough RF to microwave even a microbe. Caveat: The radar is a much shorter wavelength than the HF so there is a greater chance that something in the pacemaker might be close to, say, half or a quarter of a wavelength at 3cm and therefore close to resonant.

What does help you with the HF side is that the wavelength is many multiples of the length of any conductors in a pacemaker, so they will be less likely to be resonant at the frequency or wavelength of the HF radio.
But it can still induce voltages if you are close enough, which may or may not impact on the operation of the device, there are some RF bypass systems in these devices, but I don't know how effective they are and to what sort of field strength or range of frequencies.

You might want to consult with the pacemaker manufacturer again and ask specifically how vulnerable the device is to a radiator of amplitude modulated RF with a PEP of 100W from 2 to 20Mhz and see what they think is a safe distance.

They know the characteristics of their device better than anyone, it's probably not possible to give a reliable answer without knowing those characteristics. Call the manufacturer. While you are at it, depending where your VHF antenna is, you might want to inquire about safe distances from that too, it's much shorter wavelength than the HF radio, though it's far less power, but most marine antennas exhibit at least some gain, so the Effective Radiated Power of a marine VHF set could well be somewhat more than the output power of the radio.

AussieGeoff

[Olorin]

Peter, I think you underestimate the quality of the thinking minds on this forum. I have found them to be almost omnificent in their opinions and the differences in facts they relate are caused by the differing realities they occupy. We tried the “suit of armour” approach to produce a full Faraday Cage effect but it slowed her down too much on the foredeck and we couldn’t find a PFD large enough to handle to additional weight.

AussieGeoff, thanks for the well thought out response. You’ve given us more to think about. Now she’s afraid of the VHF too.

In all seriousness, we did contact the manufacturer and they, after questions concerning broadcast power, suggested that 3 metres (10 feet) would be a safe distance.

[zeehag]

magnets reset the pacemaker. radio waves dont. magnets do. they can stop the function of pacer by shutting it off. you want to consul;t your cardiologist for further information. mine is slightly aged-- has been a few years since i worked cedars-sinai med center as a cardiology rn.

btw-- on this forum, there is info on EVERYTHING.

[AussieGeoff]

Originally Posted by Olorin

Peter, I think you underestimate the quality of the thinking minds on this forum. I have found them to be almost omnificent in their opinions and the differences in facts they relate are caused by the differing realities they occupy. We tried the “suit of armour” approach to produce a full Faraday Cage effect but it slowed her down too much on the foredeck and we couldn’t find a PFD large enough to handle to additional weight.

AussieGeoff, thanks for the well thought out response. You’ve given us more to think about. Now she’s afraid of the VHF too.

In all seriousness, we did contact the manufacturer and they, after questions concerning broadcast power, suggested that 3 metres (10 feet) would be a safe distance.

Smart move. 3M sounds reasonable, there's no gain to speak of in a backstay antenna, so the field strength drops off with distance according to the inverse square law. I remember watching one of the Radio Techs light a fluoro tube he held in his hand by holding it near the feedline of a 5kw HF transmitter. Just because you can't see it, doesn't mean it's not there.

Zeehag's comment is interesting, and she certainly has the background to know.

Consider however, that if you create an electric field, it creates a magnetic field, as the magnetic field collapses, it creates an electric field.

So what I'm suggesting is that RF induced voltages in electronics can produce unwanted effects, either by the presence of an induced electric field or an associated magnetic field. The two go together. If you hit it with enough power, the induced voltage in wiring or PCBs can be quite high, and potentially could take out low voltage devices that may be present in somthing like a pacemaker, which has both high and low voltage components IIRC. That said, I've no doubt the manufacturers build in some 'hardening' of the electronics to cope with all but the strongest induced EMF so they are probably quite hardy.

But I've seen an early electronic fuel injection system that would misfire if a vehicle with a common or garden CB radio pulled up next to it and started to transmit. It had a lot of unshielded leads and some of them were resonant at some fraction of a wavelength IIRC.

AussieGeoff

[Blue Stocking]

Originally Posted by zeehag

magnets reset the pacemaker. radio waves dont. magnets do. they can stop the function of pacer by shutting it off. you want to consul;t your cardiologist for further information. mine is slightly aged-- has been a few years since i worked cedars-sinai med center as a cardiology rn.

btw-- on this forum, there is info on EVERYTHING.

Zee--as always, I'm impressed

[senormechanico]

Go stand by the antenna, have someone key it and whistle into the mic.

If you drop dead, don't do that again.

Simple !

[SoonerSailor]

Magnets do not turn off pacemakers. A very strong magnet will put a demand pacemaker into a fixed rate mode, this is often done in surgery when electrocautery is used so the pacemaker is not "confused" by the RF energy involved. This is far far more energy coursing through tissues than you are going to pick up standing next to an antenna, and even then it does not often affect the pacemaker (even when not placed in fixed mode by a magnet).

An implanted defibrillator (current models in US) is temporarily inhibited from firing when adjacent to a strong magnet.

Chip

[zeehag]

Originally Posted by SoonerSailor

Magnets do not turn off pacemakers. A very strong magnet will put a demand pacemaker into a fixed rate mode, this is often done in surgery when electrocautery is used so the pacemaker is not "confused" by the RF energy involved. This is far far more energy coursing through tissues than you are going to pick up standing next to an antenna, and even then it does not often affect the pacemaker (even when not placed in fixed mode by a magnet).

An implanted defibrillator (current models in US) is temporarily inhibited from firing when adjacent to a strong magnet.

Chip

are you a cardiologist?? i assisted with cardiological specialties and was one of first SPECIALTY rns in arrhythmia center in cedars-sinai medical centetr in lost angels for part of my practicing ad a cardiology / icy/er /pacu rn. YES, MAGNETS ARE USED BY PHYSICIANS TO TURN OFF PACEMAKERS. i assisted with the procedure.

do not spew untruth s to folks who may just have pacers and aicd implantations. these are heavily affected by magnets. you do NOT want magnetic fields near your pacer or aicd unit. (unless yopu have the means for reprogramming and know what you are doing--WHICH IS A RARE OCCURRANCE) and DO communicate with the manufacturer (probably medrtronic) or YOUR cardiologist before you sail.

(automatic implantable cardiovertor-defibrillators)

[SoonerSailor]

I will tell you that I have regular ongoing experience with pacemakers and magnets.

I will also agree that one should always consult the cardiologist that is familiar with your particular implanted device to learn what it is safe to do.

Chip

[zeehag]

sooner-- i asked because what you SAID did not concur with what we DID in the arrhythmia unit and post op care rooms.