Suppose I have a transmitter working off a battery. I also have in the same room a receiver which does not have a power source but is a type crystal format with a set of headphones and I listen to the transmitted music. Then a second and third person comes into the room with identical wireless receivers (also no power). Does the volume on my receiver go down because the others are drawing more power from the transmitter? Or likewise does the battery of the transmitter run down quicker with more receivers?
Slightly OT - Wireless Energy
Started by ●June 5, 2015
Reply by ●June 5, 20152015-06-05
On 5.6.15 12:32, gyansorova@gmail.com wrote:> Suppose I have a transmitter working off a battery. > > I also have in the same room a receiver which does not have a power source but is a type crystal format with a set of headphones and I listen to the transmitted music. > > Then a second and third person comes into the room with identical wireless receivers (also no power). Does the volume on my receiver go down because the others are drawing more power from the transmitter? Or likewise does the battery of the transmitter run down quicker with more receivers?It depends. If the room reflects all unused radiation back (an utopistic assumption), you would be using all transmitted power, and it would be shared among the receivers. In a more realistic solution, the RF field at your receiver will not notice the field changes caused by the other receivers, as the unused field will be absorbed by the walls or leaked out of the room. -- -TV
Reply by ●June 5, 20152015-06-05
A related question. A DAC device produces multiple (infinite) images of a frequency. How come energy be infinite or should we say a receiver can detect the frequency at any point that corresponds to an image. Kaz --------------------------------------- Posted through http://www.DSPRelated.com
Reply by ●June 5, 20152015-06-05
On Fri, 5 Jun 2015 02:32:18 -0700 (PDT), gyansorova@gmail.com wrote:>Suppose I have a transmitter working off a battery. > >I also have in the same room a receiver which does not have a power source = >but is a type crystal format with a set of headphones and I listen to the t= >ransmitted music. > >Then a second and third person comes into the room with identical wireless = >receivers (also no power). Does the volume on my receiver go down because t= >he others are drawing more power from the transmitter? Or likewise does the= > battery of the transmitter run down quicker with more receivers?No and no. Same sort of question as whether a tree falling in the forest makes a sound if no one is there to hear it. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●June 5, 20152015-06-05
>On Fri, 5 Jun 2015 02:32:18 -0700 (PDT), gyansorova@gmail.com wrote: > >> Does the volume on my receiver go down because >t>he others are drawing more power from the transmitter? Or likewisedoes>the> battery of the transmitter run down quicker with more receivers? > >No and no. > >Same sort of question as whether a tree falling in the forest makes a >sound if no one is there to hear it. > > >Eric Jacobsen >Anchor Hill Communications >http://www.anchorhill.comImperceptible and imperceptible. It is more like when you draft behind a semi on the freeway to improve your mileage. Does the truck feel it? More so than your transmitter. The resonant wave on your receiving antennas will "retransmit" more than the ambient absorption of, say the walls. Your transmitter will "feel the extra load". Since your receivers are only exposed to a small fraction of the transmitting field, the effect will be truly negligible. I doubt you could even measure it with very sensitive instruments. You seem to be asking at a theoretical level. If you leave a refrigerator in a closed room with its door open, does the room get warmer or cooler? Ced --------------------------------------- Posted through http://www.DSPRelated.com
Reply by ●June 5, 20152015-06-05
On Saturday, June 6, 2015 at 2:43:03 AM UTC+12, Cedron wrote:> >On Fri, 5 Jun 2015 02:32:18 -0700 (PDT), gyansorova@gmail.com wrote: > > > >> Does the volume on my receiver go down because > >t>he others are drawing more power from the transmitter? Or likewise > does > >the> battery of the transmitter run down quicker with more receivers? > > > >No and no. > > > >Same sort of question as whether a tree falling in the forest makes a > >sound if no one is there to hear it. > > > > > >Eric Jacobsen > >Anchor Hill Communications > >http://www.anchorhill.com > > Imperceptible and imperceptible. > > It is more like when you draft behind a semi on the freeway to improve > your mileage. Does the truck feel it? > > More so than your transmitter. The resonant wave on your receiving > antennas will "retransmit" more than the ambient absorption of, say the > walls. Your transmitter will "feel the extra load". Since your receivers > are only exposed to a small fraction of the transmitting field, the effect > will be truly negligible. I doubt you could even measure it with very > sensitive instruments. > > You seem to be asking at a theoretical level. > > If you leave a refrigerator in a closed room with its door open, does the > room get warmer or cooler? > > Ced > --------------------------------------- > Posted through http://www.DSPRelated.comOk, so here is why I am asking. If I lived next door to a huge transmitter for say radio or TV I could easily harness the energy and power a few lights maybe in my home - let's say! I woudl expect that people further away from me would see a reduced signal strength because of me however. By the same token there is new work on energy harvesting which puts an energy harvesting device near the antenna of a mobile phone, harnesses some energy and feeds it back to the battery! That doesn't sound right to me from the laws of thermodynamics.
Reply by ●June 5, 20152015-06-05
On 2015-06-05 13:07, kaz wrote:> A related question. A DAC device produces multiple (infinite) images of aI still have to see a real DAC capable of that...> frequency. How come energy be infinite or should we say a receiver can > detect the frequency at any point that corresponds to an image.bye, -- piergiorgio
Reply by ●June 5, 20152015-06-05
On 2015-06-05 16:43, Cedron wrote: [...]> If you leave a refrigerator in a closed room with its door open, does the > room get warmer or cooler?If by "closed" you mean "insulated", then the room will get warmer, obviously... bye, -- piergiorgio
Reply by ●June 5, 20152015-06-05
[...snip...]> >Ok, so here is why I am asking. If I lived next door to a hugetransmitter>for say radio or TV I could easily harness the energy and power a fewlights>maybe in my home - let's say! >If so, you should move.>I woudl expect that people further away from me would see a reducedsignal>strength because of me however. >Not necessarily. If you are picking up radiation that would otherwise go into the ground, no loss in other directions. When I was reading about antenna theory last summer, I seem to remember a story about a guy doing something like you propose, and him getting a visit from the broadcasting company, maybe the FCC. I wasn't able to find it again.>By the same token there is new work on energy harvesting which puts an >energy harvesting device near the antenna of a mobile phone, harnessessome>energy and feeds it back to the battery! That doesn't sound right to mefrom>the laws of thermodynamics.As long as they are not claiming over unity, no current laws of physics are broken. I found one claim of 30% savings. I found this link among many. http://www.technologyreview.com/news/413744/wireless-power-harvesting-for-cell-phones/ Here they report harvesting 3 to 5 milliwatts, with the hope of achieving 30 to 50. This is enough to power a few small led lights. Forget about a radio (powering a speaker) or TV. Keep thinking though, it's how all great things begin. Anybody want to talk about the biological impact of non-ionizing EMF radiation? Way off topic, but important. Ced --------------------------------------- Posted through http://www.DSPRelated.com
Reply by ●June 5, 20152015-06-05
On Fri, 5 Jun 2015 13:37:43 -0700 (PDT), gyansorova@gmail.com wrote:>On Saturday, June 6, 2015 at 2:43:03 AM UTC+12, Cedron wrote: >> >On Fri, 5 Jun 2015 02:32:18 -0700 (PDT), gyansorova@gmail.com wrote: >> > >> >> Does the volume on my receiver go down because >> >t>he others are drawing more power from the transmitter? Or likewise >> does >> >the> battery of the transmitter run down quicker with more receivers? >> > >> >No and no. >> > >> >Same sort of question as whether a tree falling in the forest makes a >> >sound if no one is there to hear it. >> > >> > >> >Eric Jacobsen >> >Anchor Hill Communications >> >http://www.anchorhill.com >> >> Imperceptible and imperceptible. >> >> It is more like when you draft behind a semi on the freeway to improve >> your mileage. Does the truck feel it? >> >> More so than your transmitter. The resonant wave on your receiving >> antennas will "retransmit" more than the ambient absorption of, say the >> walls. Your transmitter will "feel the extra load". Since your receivers >> are only exposed to a small fraction of the transmitting field, the effect >> will be truly negligible. I doubt you could even measure it with very >> sensitive instruments. >> >> You seem to be asking at a theoretical level. >> >> If you leave a refrigerator in a closed room with its door open, does the >> room get warmer or cooler? >> >> Ced >> --------------------------------------- >> Posted through http://www.DSPRelated.com > >Ok, so here is why I am asking. If I lived next door to a huge transmitter for say radio or TV I could easily harness the energy and power a few lights maybe in my home - let's say! > >I woudl expect that people further away from me would see a reduced signal strength because of me however.Only if you created a shadow by blocking the signal like a building or other big object. Othewise you'll have no effect on whoever is "behind" you.>By the same token there is new work on energy harvesting which puts an energy harvesting device near the antenna of a mobile phone, harnesses some energy and feeds it back to the battery! That doesn't sound right to me from the laws of thermodynamics.Same thing. If it distorts the near field or shadows things downstream that would otherwise like to receive the signal, it can be counterproductive. Cell phones are power controlled by the base station they're communicating with, so if you stick one of those things on there and it unfavorably distorts the antenna pattern (by near-field proximity) or shadows the base-station receiver, the base station will turn up the transmit power on the cell phone to compensate. So it can be very counter-productive. It is true that point-to-point links with an omnidirectional antenna on at least one end tend to waste a lot of Tx power by sending signal lots of places it doesn't need to go. This is being addressed to some degree in some systems by beamforming techniques. Even with beamforming a lot of power goes where you don't need it, but there's only so much you can do with limited antennas. Handsets (e.g., cell phones) are typically too small to employ that sort of thing in their transmit signal, so it's mostly done at the base station. WiFi equipment that is large enough and has many antennas can do it to a degree, but, still limited. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com