Thanks KoRn. Wow, am I behind or what? Anyway, could be of interest to the C list.
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Posted on 04/11/2015 10:29:03 AM PDT by LibWhacker
>> asymmetric excitation <<
Hmm. Reminds me of a certain old girlfriend!
>> The reception is still going to be limited by the capture area <<
What about ferrite-core loopsticks? They occupy a tiny space but pick up a lot of signal.
As a 30-year veteran RF circuit design engineer, I'm highly skeptical of this article. But they might be on to something. Time will tell.
Nope, not at the speed of light in a vacuum, anyway. Even silver, best conductor in nature, slows them down a bit.
But the loopstick is only one of a class of electrically-small antennas (small compared to the wavelength in free space). Electrically-small antenna theory has been fairly stable since the 1960's, though there has been some minor refinements.
“But the loopstick is only one of a class of electrically-small antennas (small compared to the wavelength in free space). Electrically-small antenna theory has been fairly stable since the 1960’s, though there has been some minor refinements. “
Electrically small antennas have poor gain figures. For the purposes of many ferrite loop/stick antenna applications this is “good enough” - plus you can get a little directivity to null out interference to make up for sub-optimal gain.
The trick here, if I’m reading between the lines correctly, is that you’re getting an electrically resonant antenna in a small dimensional footprint but avoiding the penalty of very low gain.
Looking forward to more on this topic.
>> Ferrite-core loopsticks are good for only low-frequency signals <<
If you’re referring to the loopsticks’ current sizes, I get it.
But what if they could be scaled down in proportion to wavelength?
For example, let’s say a current loopstick optimized for 300 meters (middle of the MW broadcast band) is three inches long. So what about a loopstick for the three cm band — which (if my calculations are correct) would be 3/10000th of an inch long?
(And I guess the “wires” wrapped around the ferrite core would be smaller by maybe a factor of ten to the minus three.)
Clearly, the manufacturing process for something that tiny is hard to imagine.
On the other hand, maybe it will eventuate some day, because nano-technology has already accomplished so many other tricks that defy the imagination.
Hmm, I’ve never had that problem and I’ve probably lived in a dozen different places in my lifetime with automatic garage doors. In my current house, I can open the garage door from anything less than about half a block away, although I do notice it’s highly sensitive to how fresh the batteries are in my opener. When I have to get as close as my next-door neighbor’s house, I’ll usually swap out the batteries for new ones. Other than that, it’d be interesting to know which make and model you have (so none of us Freepers ever make the mistake of buying one!).
One of the posters at the phys.org site said, “Warning: Antenna products and research are subject to more snake-oil salesmanship than most other fields,” and I think he’s probably right. I was excited because of the thing about symmetry breaking. I thought some new physics had been discovered. Should’ve known better.
It isn’t the opener or the batteries. Metal building. I tried connecting to an external antenna wire but it doesn’t help.
Much truth here. Remember all the hype about fractal antennas? People claimed they would violate Wheeler and Chu's limits on electrically-small antennas. Well, they didn't, and in some cases, they didn't even work as well as previous electrically-small antenna designs.
Thanks KoRn. Wow, am I behind or what? Anyway, could be of interest to the C list.
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Thanks KoRn. Superconductivity ping.
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