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Groups > sci.physics > #534017
| From | jimp@specsol.spam.sux.com |
|---|---|
| Newsgroups | sci.physics |
| Subject | Re: long antenna |
| Date | 2015-11-19 05:29 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <2a30ic-rud.ln1@mail.specsol.com> (permalink) |
| References | (1 earlier) <n2fsm5$ms8$1@speranza.aioe.org> <4736856.kWDMch3Bm0@PointedEars.de> <n2ivpn$gh9$1@speranza.aioe.org> <fddvhc-vob.ln1@mail.specsol.com> <n2jcuf$9qr$1@speranza.aioe.org> |
gilber34 <fafa@invalid.com> wrote: > On 11/18/2015 5:15 PM, jimp@specsol.spam.sux.com wrote: >> gilber34 <fafa@invalid.com> wrote: >>> On 11/18/2015 3:56 PM, Thomas 'PointedEars' Lahn wrote: >>>> Odd Bodkin wrote: >>>> >>>>> On 11/17/2015 12:42 PM, RichD wrote: >>>>>> During my workout yesterday, I attached a 3 meter >>>>>> extension to the earphone cord of my radio, as I >>>>>> wanted to place it at a distance. >>>>>> The cord is the antenna. >>>>>> >>>>>> I was indoors, where the reception is usually crummy. >>>>>> I figured the longer line should improve performance, >>>>>> right? No! The reception was barely decipherable. >>>>>> >>>>>> Can anyone explain the physics here? >>>>> >>>>> Yeah, it's pretty simple. The earphone is attached to an OUTPUT of the >>>>> radio. The only valuable place to stick an antenna is on an INPUT to the >>>>> radio. >>>> >>>> Wrong. >>>> >>>>> Signals-->||-->Tuner-->Amplifier-->Analog driver-->||-->Earphones >>>>> <----------- Radio -------------------> >>>>> >>>>> See where the antenna goes? >>>> >>>> Not only is your answer wrong, you also missed the point of the question. >>>> >>>> As the OP indicated, earphone (also: headphone) cords contain wires which >>>> can serve as antennas. >>> >>> .....well, they do connect to the Head which serves as the big resonae >>> cavity Antenna. a large round semi conductive salt vat on your sholders, >>> full of liquid up in the air. >> >> Nope. >> >>> [They certainly do with smartphones (from where I >>>> know the technology): Once you have plugged the headphones into the >>>> smartphone, you can start a radio app to tune in to FM (frequency >>>> modulation) radio channels (*without an Internet connection*). [0] >>>> It stands to reason to use the same technology elsewhere.] >>>> >>>> How does radio, how does an antenna work? Radio is based on the >>>> transmission and reception of radio waves carrying information piggybacked >>>> on them through modulation of them. >>> >>> no piggies were harmed... >>> >>> >>>> Therefore, the >>>> longer line does _not_ improve reception quality of a particular radio >>>> channel (its station transmitting at a particular frequency) to begin with. >>> >>> that is, in general, a wrong statement. larger capture area means more >>> signal power. >> >> Nope; grossly oversimplified to the point of being wrong. > > yep, oversimplified for sure. Need the frequency band. Nope; irrelevant to the original statement. >>>> I also think that the longer the line the more likely that there is >>>> interference, i.e. alternating, partially canceling electrical currents >>>> induced at different points of the cable as the (peak of the) radio waves >>>> can hit the cable at those points at different times, and interference from >>>> other sources. >>> >>> they dont "hit" the cable. >> >> They sure don't go around the cable. > > "hit" an antenna is not used in the industry, > look it up in Kraus, its a summation of currents, etc. etc. While not generally used, hit is a synonym for words that are. >>>> Finally, electrical resistance of a conductor R = ρl∕A, >>>> where ρ is the material-dependent electrical resistivity and A is the cross- >>>> sectional area, is proportional to the length l of the conductor [8], so the >>>> signal that reaches the tuner should become weaker as the cable length >>>> increases. >>> >>> wrong. (match the impeadance, Hint: it is a complex term. lots of free >>> programs out there on antenna design if you are interested.) >> >> About the only thing correct so far. >> >>>> However, I understand that there are also traveling wave antennae that are >>>> nonresonant, like random wire for receiving shortwave radio. [9] > > one can use an antenna with a preamp and forget matching, however the > preamp will be a mixer, with the LO supplied by FM, TV stations or other > if around, providing inteference. Total nonnsense. Mixing requires a non-linear device and preamps are built to be linear devices. Matchins still important to preamps. > So it >>>> appears to depend on the frequencies that one wants to receive. I would >>>> like someone with experience in radio technology to add their expertise >>>> here. And please, CMIIW. >>>> >>>> >>>> PointedEars >>> >>> depends upon what frequency band you are looking at. >>> FM - you usally will get blasted out by high power stations, over >>> loading your very cheap chinese receiver. >> >> FM stations are not usually high power as the FM band is essentially >> line of sight and does not depend on either ground wave or sky wave >> propagation as AM does. >> >> > > not so, FM power is HUGE. The ERP tends to be huge in urban areas. > and remember FM is frequency is 200 times AM, and probagation is very > different, still good compaired to 800 MHz. BUT the main thing with FM > is that system was designed so one could use cheap low cost receivers, > so transmit power is high, and the receivers do not have much > selectivity, and rely on an effect called "capture". if you have two > stations on the same frequency, but one is 10Db lower in power, the > higher power one will swamp out the low power one, and you will hear > only the high power one. (not so with AM, you hear both) Most of that is just nonsense. > he said he was listening to FM, so he is in a city, There are lots of FM stations outside major cities these days. > but break out your spectrum analyser and see how huge the FM station > power is, larger than any other, except for some TV channels > > I would do it and send a photo, but my analyser when last turned on, let > out some smoke in the back, and no workie now. (smoked a resistor in the > power section somewhere) Not surprising given your level of RF knowledge. -- Jim Pennino
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long antenna RichD <r_delaney2001@yahoo.com> - 2015-11-17 10:42 -0800
Re: long antenna Odd Bodkin <bodkinodd@gmail.com> - 2015-11-17 12:46 -0600
Re: long antenna Poutnik <poutnik4nntp@gmail.com> - 2015-11-17 20:10 +0100
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-17 20:28 +0000
Re: long antenna benj <nobody@gmail.com> - 2015-11-17 16:59 -0500
Re: long antenna Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-11-18 22:56 +0100
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-18 16:57 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-18 23:15 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-18 20:42 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-19 05:29 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-19 08:54 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-19 18:44 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-22 15:32 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-22 23:16 +0000
Re: long antenna HVAC <mr.hvac@gmail.com> - 2015-11-19 06:59 -0800
Re: long antenna benj <none@gmail.com> - 2015-11-19 20:02 -0500
Re: long antenna benj <none@gmail.com> - 2015-11-19 01:36 -0500
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-17 13:28 -0600
Re: long antenna "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-17 14:04 -0800
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-17 22:35 +0000
Re: long antenna benj <nobody@gmail.com> - 2015-11-17 19:28 -0500
Re: long antenna Timo <timo@physics.uq.edu.au> - 2015-11-17 17:18 -0800
Re: long antenna RichD <r_delaney2001@yahoo.com> - 2015-11-24 11:39 -0800
Re: long antenna benj <none@gmail.com> - 2015-11-24 15:12 -0500
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-26 09:21 -0600
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-26 10:05 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-26 20:05 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-26 18:39 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-27 01:46 +0000
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-26 19:55 +0000
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-24 20:04 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-24 16:33 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-24 22:58 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-26 09:11 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-26 19:42 +0000
Re: long antenna "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2015-11-26 11:57 -0800
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-26 14:52 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-26 21:12 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-26 18:58 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-27 01:37 +0000
Re: long antenna benj <none@gmail.com> - 2015-11-26 23:45 -0500
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-27 01:01 -0600
Re: long antenna "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2015-11-26 23:31 -0800
Re: long antenna benj <nobody@gmail.com> - 2015-11-27 11:34 -0500
Re: long antenna "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2015-11-27 09:58 -0800
Re: long antenna benj <nobody@gmail.com> - 2015-11-27 11:46 -0500
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-28 16:42 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-28 22:58 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-30 07:46 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-30 19:01 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-30 14:12 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-30 20:43 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-30 17:41 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-12-01 00:15 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-30 20:23 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-12-01 06:21 +0000
Re: long antenna benj <none@gmail.com> - 2015-11-30 15:22 -0500
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-30 20:48 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-30 17:16 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-30 23:52 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-30 19:59 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-12-01 02:16 +0000
Re: long antenna benj <none@gmail.com> - 2015-11-30 19:20 -0500
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-27 18:53 +0000
Re: long antenna benj <none@gmail.com> - 2015-11-25 00:08 -0500
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-25 06:13 +0000
Re: long antenna "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-18 16:25 -0800
Re: long antenna "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-19 16:08 -0800
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-20 00:40 +0000
Re: long antenna "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-20 15:51 -0800
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-21 00:34 +0000
Re: long antenna jmfbahciv <See.above@aol.com> - 2015-11-21 14:37 +0000
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-21 19:32 +0000
Re: long antenna jmfbahciv <See.above@aol.com> - 2015-11-22 14:50 +0000
Re: long antenna "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-22 11:27 -0800
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-22 19:44 +0000
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-22 19:40 +0000
Re: long antenna jmfbahciv <See.above@aol.com> - 2015-11-23 14:13 +0000
Re: long antenna benj <none@gmail.com> - 2015-11-23 13:00 -0500
Re: long antenna jmfbahciv <See.above@aol.com> - 2015-11-24 13:20 +0000
Re: long antenna benj <none@gmail.com> - 2015-11-24 13:40 -0500
Re: long antenna jmfbahciv <See.above@aol.com> - 2015-11-25 13:44 +0000
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-23 18:47 +0000
Re: long antenna jmfbahciv <See.above@aol.com> - 2015-11-24 13:20 +0000
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-24 19:49 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-24 16:36 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-24 23:00 +0000
Re: long antenna gilber34 <fafa@invalid.com> - 2015-11-26 16:17 -0600
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-26 23:35 +0000
Re: long antenna benj <none@gmail.com> - 2015-11-20 20:58 -0500
Re: long antenna benj <none@gmail.com> - 2015-11-19 20:09 -0500
Re: long antenna "nuny@bid.nes" <Alien8752@gmail.com> - 2015-11-24 12:51 -0800
Re: long antenna benj <none@gmail.com> - 2015-11-25 00:01 -0500
Re: long antenna "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-25 15:36 -0800
Re: long antenna jimp@specsol.spam.sux.com - 2015-11-25 23:51 +0000
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