Hi Gentlemen,
I was brought up in RF communications. I hold an FCC 1st Class Radiotelephone license and have worked in commercial-FM radio, Navy HF UHF and business microwave.
First, I just love you guys, and the answers you come up with are truly an “Art Form”
I have some possibilities to suggest(Most Engineers call “RF” a “Black Art” form of electronics).It is not always easy to understand the results observed.
The reason the range is short might just be a weak battery. I don’t remember hearing if it was changed, and if it had a “fresh cell” or one hanging in the back of a gas station for ten years or the local dollar store.
Raising the remote keyless device to a chin level rather than waist level may also increase the “line of sight” angle between transmitter and receiver.
3.The folks with the “beam reflection” may be right, but I am skeptical.
Thank you for keeping my brain active, and my funny bone tickled.
Don’t try to confuse me with your “science.” Here’s how it really works: The signal from the fob aimed at your chin interferes with the alien microchip in your brain, causing bad feedback. The aliens then open the car door just to shut you up for a while. Hope that helps.
p.s. Handy tip: Anyone who tells you different is one of them.
Hello all, I listened the Dave’s Keyless remote segment with chagrin and awe as the boys tried to explain this away with sillier and seller methods.
I work as a manager of Technical support for an American manufacture of home automation systems, (such as control processors, touch panels and web based interfaces - see www.crestron.com for more details), of which many of our products utilize both IR and RF transmissions. The issue described is very similar to calls we get insisting such and such panel or gateway is not working. (Although some callers do not always express the situation in such gentle terms).
One of the most basic operations of antenna systems, especially omni directional Yagi types, is to remember that antenna orientation and placement are crucial to reliable reception.
Contrary to popular belief, the strongest point of transmission - and reception for that matter- comes from the “sides” of the antenna. Not the tips.
While I could not find a schematic of the key fob in question I think the answers lies with how the fob antenna is orientated and what this does with line of site clearance.
Most likely the fob’s antenna is located on the underside of the fob. This would make sense, as it would provide the greatest surface area to place the strip. When pointing the remote directly at the car, with the ‘head end’ pointing directly at the car you are in effect directly the majority of signal downward and only a small weak signal toward the car and its reception antenna. By bringing the fob up to ones chin you effectively increase the
1). Line of site for the antennas
2). Expose more of the main antenna transmitting surface toward the car. Such would hold true if you hold the fob vertical - with head end pointing at your chin- or horizontally- head end pointing toward car.
Both increase the reception antennas exposure to the main transmitting antenna surface, ie the sides. By holding vertical to the chin you are directly transmitting to the car. By holding the fob higher you are also accomplishing the same thing, though probably not as much, by increasing the line of site exposure.
This is why a previous poster stated that their fob worked at 10’ on the ground and 100’ from an office window.
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Dear Click and Clack,
Well, I always knew that listening to Car Talk for so many years would one day pay off and that day has finally come. I’ve reaped the rewards my loyal listening, and the reward has been well worth the wait. I can’t speak to exactly what’s happening with “The Dispersion Theory,” but without a doubt, something is going on. After hearing about it on your show I just had to try it out on my tv. Sure enough, when I pointed my television remote away from the tv, on it went. When I pointed it 180 degrees in the opposite direction (but towards the required wall for the signal to bounce off of) the television went on flawlessly. Well, sitting next to my television is my iHome, which is a combination iPod charger, radio tuner and alarm clock, and music player for the iPod. The problem has been that each time I pointed my remote at the tv, it turned on the iHome radio alarm clock, whereupon I would have to get up off my comfortable bed from where I had turned on the television with the remote and shut off the radio alarm, lest I forget to do it later and have it wake me up in the dead of night. Well, to turn on the tv with a remote while lying in bed, then immediately get up to turn off the clock alarm one half second later defeats the purpose of using a remote for the tv in the first place. Because of the way in which the television and the iHome are placed with relation to each other, thanks to the Dispersion Phenomenon, I can point my tv remote out the window of my bedroom, have the television itself block the signal to the iHome as it bounces off the window and turn on the tv without setting the radio alarm on the iHome. While I’m not sure what else my television remote is turning on in the neighborhood when I point it out my bedroom window, what I do know is that you guys finally helped me solve an annoying problem with my tv and iHome. You guys are hilarious, and now as I can personally attest, not only car mechanics par excellence but top-notch problem-solvers in the world of home electronics. Thanks for all the laughs and for filling us in on the many useful applications of the Dispersion Phenomenon.
Yours truly,
A Loyal Listener
While I find your suggestion interesting I am a bit confused as to how this could possibly work.
Given the power ratios of the RF signal and the absorbstion rate the average brain and surrounding tissue would provide, the effect could not possibly take place.
The power to create such and effect would fry a persons brain, not to mention the burn marks on skin, before successfully bouncing the signal out.
The fact that the transmitted signal is a relativly low UHF wavelength still does not give this theory a chance at the transmission power we are discussing.
From a physics point - just how would you justify this?
I went to the Discovery Web Site today and that is actually in a forum for a requested show. Who knows, maybe someday they will follow up on it and come up with their conclusions.
Precisely. In fact the signal probably bounces between the frontal and occipital bones multiple times, creating, in effect, a cranial laser which sends out a coherent and amplified signal. Thanks for pointing that out.
By the way, I have a further refinement of my hypothesis- With the dielectric differential between tooth enamel and the metallic amalgam of cavity fillings, I believe there’s a strong potential for further signal amplification. By my calculations, it could be up to an order of magnitude; but I’ll wait for empirical verification trials. I should also like to test sucking a foil gum wrapper.
Thank you for the thoughtful conversation. For now, there are pressing matters to attend to. So, if you’ll excuse me, I must return to the laboratory.
Zozmaa, your response is good, I wish I’d seen it before I posted mine. You beat me to it. We must have been typing in parallel, and I’m slower (and more pedantic)
Sean, my apologies for not mentioning the details of antenna radiation patterns from dipoles or simple loops. You are absolutely correct that the strength and pattern of the RF field depends on the orientation with respect to the antenna as you describe(and the distance from the antenna, far and near field). I didn’t want to get into it as I thought this might muddy the waters. The key element I wanted to emphasize was that the radio waves radiate in almost all directions compared to an IR remote. The little RF transmitter will emit radio waves that will interact with the body as a whole.
Finally! At least two people have mentioned the true cause of this effect! Everybody has searched through scientific theory to come up with the most complex, impressive explanation possible while completely overlooking the obvious!
As mentioned before, transmitters work best in “line-of-sight”. If you are holding your fob at your waist, it’s probably below the receiver. If you point it at your chin, the signal is now being bounced from a point above and more in line with the receiver. This also explains why it works from a high position such as an office-building. Oh, since everyone is mentioning their credentials I suppose I should give mine. I’m a truck-driver! Got any other problems you need solving?
Apparently, everyone has gone to great lengths to try to come up with the most impressive answer with the most backing-information. Unfortunately, everyone has bypassed the obvious explanation.
The transmitter and receiver operate on “line-of-sight”. When you point the transmitter at your chin, the signal is being bounced from a higher vantage point. This also explains why it has worked from office buildings and why reflecting your TV remote off your face (which is higher than the rest of your body and more in line with the receiver)works. My credentials? I’m a truck-driver. Got any other problems needing solving?
Well, I didn’t realize there would be this many theories. Since the keyless remotes are RF rather than IR transmitters, I think it may just be that the signals propagate better perpendicular to the antenna, which is probably a trace on the printed circuit board inside the Fob.
By pointing it at your chin, you’re probably orienting the Fob such that the antenna is perpendicular to the car so the receiver in the car is presented with a stronger signal.
Try pointing it in the same orientation at arms length and see if you get the same increase in range.
Given the conductivity and permissivity of human tissue, I don’t see how a human head could amplify a signal…unless you’re wearing a solar powered tin-foil hat.
I still like CatalyticConverser’s “cranial laser” hypothesis. Maybe I was the only one, but thoroughly cleansed my sinuses with diet coke when I heard the dispersion theory on the radio. I wish I had one of these fancy locks on my car so that I could test the effects of intra-cranial carbonation on RKE signal amplification.
