Not in the unlicensed bands under the restrictions of power, etc.
Others have said that. Is that not clear or is there another issue? 443MHz (or maybe 433MHz?) is unlicensed and you can buy many, many transmitters and receivers on eBay or Aliexpress.
-- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
t.
I have wondered about RFI in the AM band from EVs. It only struck me after I found Tesla doesn't include AM reception in their cars. Maybe that's be cause you wouldn't be able to hear much unless you were next door to a 50,0
00W transmitter. If I ever find another AM receiver I may try it next to t he car see how bad it is. I don't know where I heard it, but I recall a nu mber of 30kHz for a typical motor excitation frequency in Teslas.-- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
It seems Teslas can make some cool noises on the AM band:
-- Regards, Joerg http://www.analogconsultants.com/
Diodes can do strange things. They can make huge reverse snap impulses. A solar panel looks a lot like an antenna.
And a diode or a mosfet connected to a lot of wiring in a power circuit becomes a variable-gain reflector that modulates ambient RF. I don't think that any EMI certifications consider that effect.
eft.
r I found Tesla doesn't include AM reception in their cars. Maybe that's be cause you wouldn't be able to hear much unless you were next door to a 50,0
00W transmitter. If I ever find another AM receiver I may try it next to th e car see how bad it is. I don't know where I heard it, but I recall a numb er of 30kHz for a typical motor excitation frequency in Teslas.an AM radio would fit right next to the cassette player or is that too mode rn, an 8-track maybe?
The solar panels that are a big problem are the ones with micro-inverters. Passive solar panels are quieter than mice.
CH
I wonder if the topography, basically an elliptical dish between us, focusses the RF.
I've got to see if there's enough RF to light an LED. The circuit issues could be interesting, for harvesting wideband RF.
-- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
That's what capacitors and ferrite were invented for :-)
EMC is quite clear and limits have to be maintained no matter what the mechanisms. All this can be properly dealt with by a competent engineer with RF background and it doesn't even have to be expensive. However, there is no regulation to write home about for 0-30MHz radiated and that's a serious problem. "Down there" only conducted emissions are measure unless you are designing mil or aerospace gear.
Yes, those can be especially bad. Often cheap electronics designed by rookie engineers and then let loose into the wild.
Not so much around here. I've got one that produces a 2-3kHz swath of noise every 200kHz and another every 60kHz. Unfortunately not stable, both of them move around so you think you have a clear frequency and half an hour later it creeps in from the side.
-- Regards, Joerg http://www.analogconsultants.com/
Nah, nowadays there'd be too much RF loss from tents, poop, sleeping bags and so on :-)
You just need a big enough antenna and catch the right spectrum. Then maybe a Skyworks sampling diode and an efficient LED.
-- Regards, Joerg http://www.analogconsultants.com/
I had a home-made crystal-set radio when I was a kid, with a longwire antenna in the back yard. It was blaringly loud into a set of hi-z headphones. Easily enough power to light an LED, from just one selected radio station, which wasn't even especially close.
-- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
ESP32
The strange thing about FCC is that if it is an intentional radiator is has to be approved for with all kinds of rules, even if you stay below the EMI radiated limits
If you have a noise source, also a radiated, just not intentional, then you just need to stay below the EMI radiated limits, no extra stuff
Wrt noise, what is really the difference?
No radiated EMI test will see anything from a modulated reflector.
-- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Interesting indeed! Monster dish arrays. I wonder what the potential yield could be?
On 13/02/2021 12:15 pm, Joerg wrote: [snip]
Does the TV horizontal sweep oscillator still trash the HF (2-30 MHZ) ham bands?
At such short distance, the VHF/UHF path loss calculated from the Friis transmission equation is not very large, so quite strong individual signals can be expected.
The problem in calculation is guessing what the actual EiRP for each individual transmitter is towards angles below the horizon.
How much current does a modern LED require to be usable ? 100 uA ?
A parabolic reflector a few wavelengths in diameter should do collecting the power from all transmitters perhaps up to 0 dBm (1 mW which is 220 mV into 50 ohms). You would need a wide band step up transformer to generate at least 3 Vpp.
How well does the LED work as a rectifier at VHF/UHF ? In the simplest case, just put a series capacitor between the step up transformer and LED and connect the other LED end to ground.
On a sunny day (Sun, 14 Feb 2021 10:21:08 +0200) it happened snipped-for-privacy@downunder.com wrote in :
In the Land Of Lawyers (L.O.L.) you may well be sued for stealing power from that station
In another case, an engineer living at a military base in England lived in a house near a radar installation. He installed induction coils in his attic that generated electricity from the radar beam. Controllers in the radar facility noticed a strange shadow on their screens and he was caught.
I do not believe in this story, If it had happened in Australia in very rural areas with single wire medium voltages lines with ground return. Putting a wire parallel to the line and some power will be capacitively connected from the line to the wire.
As far as I understand, in the rest of the world medium/high voltage lines are three phase and the distance between phase conductors is small compared to the distance to the ground. on the ground the phase voltages cancels quite well,, so there is not much to extract. With EHT lines with phase conductors that are many meters on opposite side of the pole, you might get something into the wire close to the ground.
On a high voltage line the capacitance to ground varies with soil type and water content, so I do not expect that the power company could detect the theft. Of course, Perhaps the farmer bragged about it and some neighbor reported it...
Usually radars remove static clutter and only display moving objects. Again, apparently the person bragged about his system publicly.
On a sunny day (Sun, 14 Feb 2021 13:11:33 +0200) it happened snipped-for-privacy@downunder.com wrote in :
An IF bandwidth that wide will hide a lot of stuff. It looks like there's another spur about -59 dBm at 58 MHz or so. I assume you had a closer look?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
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