kland,

Having some knowledge in the realm of radio transmission, I would say that simply cranking up the power on the base transmitter will not make the signal from the chip equally responsive. You are working with three big limitations, which really boil down to one word--size.

1) The tiny size of the implanted chip restricts the amount of antenna which it can contain;
2) This in turn limits the amount of electric power which can be harvested from the incoming signal and converted to an outgoing transmission; and
3) The outgoing signal is limited to a small range by both the shortness of the antenna and the shortness of the wavelength on the signal.

Longer-wavelength signals require longer antennas to transmit them. However, there are advantages and disadvantages to both longer and shorter wavelengths. Longer wavelengths can travel greater distances. Shorter wavelengths can penetrate better through various types of matter.

My guess is, due to the chip size, we are working with some very short wavelengths (high frequencies) for transmission. This will be good at penetration--no problem going through flesh, bones, some wood or plastic, a wall, etc. But this will not be worth much at a distance.

If you crank up the power on the base station transmitter, the chip will have an increased response up to a certain point, at which these physical limitations prevent any further benefit. You might have a chip that was receiving the signal from across the room, but was still unable to transmit it more than a few feet. One-way communication as this would be worthless. Exactly how many feet could they get out of an RFID chip? That depends much on the chip design, especially that of the antenna coil and length.

Now, if they could figure out a way of "harvesting" some natural "body antenna" by plugging the chip into it...would nerves work? I think most any organic material of the body would present too much impedance to make a proper antenna, not to mention the fact that bodies come in many sizes, so the antennae would not be well tuned.

Blessings,

Green Cochoa.

Maybe cutting it off would be less painful?

Hi Kland,

The technology has long been discussed in engineering journals. The subject is old hat in the industry. Truckers use window-sticker RFIDs to expedite border crossing checkpoints; consumer products have the chips for warehouse inventory & customer databases - think Walmart. Railway cars in the switching yards - you get the picture. Human RFID tracking has been used for ~ 5 years in prisons & hospitals - bracelet or implant. Passive tags are low range; active (battery-powered) up to several hundred feet, maybe more.

RFID Journal: http://www.rfidjournal.com/faq

Katherine Albrecht is one of the foremost consumer educators:

http://www.nocards.org/

http://www.spychips.com/
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So if more power does give further distances in sending the request, what happens to the response signal? Does it abruptly stop or gradually fade away as it travels across the room? In other words, if a more sensitive receiver was used, would it be able to pick up the signal if no other interference?

kland,

That's a good question. Again, listening sensitivity can be improved, but only to a point. The point at which it fades out is the point at which the desired signal essentially blends with the ordinary "noise." Keep in mind that our ambient surroundings are continuously filled with radio waves, on many frequencies. Even from our sun and from space we receive certain levels of radio activity. Due to the radiant energy of the sun, our atmosphere's "F layer" splits during the daytime into two layers called the F1 and the F2 layers. At night, they rejoin into a single layer which is better able to bounce back and to retain radio transmissions (esp. useful for frequencies in the 10 - 40 meter wavelength spectrum, which can be transmitted through the night side of the earth fully half-way around). Thus, during the day, and especially if there are solar storms, also called "sun spots," there is more radio "noise."

Gordon mentioned the distinction between "active" (battery-powered) and "passive" (receives power from the incoming radio waves) RFID chips. Many of them are "passive," since batteries have a limited life, and are bulky and heavy. In this sense, a good example that may help you to understand the limitations might be to look at light for a minute.

A flashlight would be an "active" light source, since it is powered by a battery. However, the "glow in the dark" stars on your child's ceiling would be "passive." These do shine a little brighter if first hit by a brighter light, but only to a point. They can never hope to shine as brightly as the flashlight, even if they were blasted by the light of an arc welder.

If the room already had a nightlight on the wall, would the light from the glowing stars on the ceiling make a noticeable difference in the amount of light hitting the page in the book you were trying to read in that dim room? Would you be able to increase your eyes' sensitivity to notice the difference? Electronics also has its limits with sensitivity. Part of this involves the "noise" of the electric circuits themselves. It takes a great deal of circuit engineering and expense (maybe a little gold?) to produce the clearest electronic signals. Noise may have its biggest impact in technologies such as video camera CCUs, audio equipment, professional organs and keyboards, etc. But electronic noise is a problem for thousands of applications. Consider modems, for example. If noise were no issue, modem speeds might be a thousand times faster than they are today.

(Now I've unintentionally written an epistle already, when you probably wanted a two-sentence answer. My apologies.)

Blessings,

Green Cochoa.

Kind of on a side note, but figured maybe you could answer this about radio waves. There is an AM radio station not that far away which we pick up with pretty good reception. That is, until the sun sets. Some AM stations sign off, but this one continues broadcasting. The signal gets a little bit of static, I notice the sun has almost set, then the signal fades as quickly as the sun sets. I would expect a more gradual loss if any. Does this have something to do with a reverse of what you were saying about the F layer joining? It's almost like the light hitting or not hitting something makes an on/off difference. I also have noticed being able to pick up stations as far as half the US away at night, though it comes and goes reminding me of sine waves syncing and un-syncing. ("Resonance", is that the word?)

kland,

The separation of the F-layer into two layers is caused by the sun. I never studied nor learned how quickly these layers are separated and rejoined. Your experience is interesting. I do know, however, that they must join fairly quickly, as it is possible to circumnavigate half-way around the world through the night side with radio waves of the right frequency.

What you experience with the radio during the daytime may be related to one of two phenomena, the most likely being the one called "skip." Radio waves can bounce off the atmosphere. When the F-layer is all a single layer, AM radio can skip a long ways, something like skipping a rock on water. However, radio waves can also skip, to a lesser degree, on the split layers. The layering changes the altitude at which the skip occurs, and some layers may tend to absorb the radio waves, instead of conducting them (permitting them to pass).

The following website gives a nice chart of some radio frequencies and which layers, if any, of the atmosphere they are affected by.

http://en.wikipedia.org/wiki/Radio_propagation

Blessings,

Green Cochoa.