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Groups > sci.physics > #533801 > unrolled thread
| Started by | RichD <r_delaney2001@yahoo.com> |
|---|---|
| First post | 2015-11-17 10:42 -0800 |
| Last post | 2015-11-25 23:51 +0000 |
| Articles | 20 on this page of 95 — 14 participants |
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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
Page 1 of 5 [1] 2 3 4 5 Next page →
| From | RichD <r_delaney2001@yahoo.com> |
|---|---|
| Date | 2015-11-17 10:42 -0800 |
| Subject | long antenna |
| Message-ID | <d82a6d99-39d1-4eb7-9aa0-4ed38641537a@googlegroups.com> |
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? -- Rich
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| From | Odd Bodkin <bodkinodd@gmail.com> |
|---|---|
| Date | 2015-11-17 12:46 -0600 |
| Message-ID | <n2fsm5$ms8$1@speranza.aioe.org> |
| In reply to | #533801 |
On 11/17/2015 12:42 PM, RichD wrote:
> During my workout yesterday, I attached a 3 meter
> extension to the earphone cord of my radio, as I
> wanted to place it at a distance.
> The cord is the antenna.
>
> I was indoors, where the reception is usually crummy.
> I figured the longer line should improve performance,
> right? No! The reception was barely decipherable.
>
> Can anyone explain the physics here?
Yeah, it's pretty simple. The earphone is attached to an OUTPUT of the
radio. The only valuable place to stick an antenna is on an INPUT to the
radio.
Signals-->||-->Tuner-->Amplifier-->Analog driver-->||-->Earphones
<----------- Radio ------------------->
See where the antenna goes?
>
> --
> Rich
>
--
Odd Bodkin --- maker of fine toys, tools, tables
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| From | Poutnik <poutnik4nntp@gmail.com> |
|---|---|
| Date | 2015-11-17 20:10 +0100 |
| Message-ID | <n2fttt$l7g$1@dont-email.me> |
| In reply to | #533802 |
Dne 17/11/2015 v 19:46 Odd Bodkin napsal(a): > 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. > > Signals-->||-->Tuner-->Amplifier-->Analog driver-->||-->Earphones > <----------- Radio -------------------> > > See where the antenna goes? > Many phones provided with FM modul use earphones as an external antenna. I suppose while it is the output, there is also a filter, passing the VHF signal by a loopback to the VHF input. A proportionality between antenna gain and size is valid only for the size << signal wavelength. For FM 100 Mhz is wavelength about 3 m. So the typical earphone cords are very close to lambda/4. A typical antenna length is lambda/4 or lambda/2. 3 m + orignal length is too long, providing worse output, than original cord. -- Poutnik ( the Czech word for a wanderer ) Knowledge makes great men humble, but small men arrogant.
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| From | jimp@specsol.spam.sux.com |
|---|---|
| Date | 2015-11-17 20:28 +0000 |
| Message-ID | <v8fshc-rs1.ln1@mail.specsol.com> |
| In reply to | #533802 |
Odd Bodkin <bodkinodd@gmail.com> 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. > > Signals-->||-->Tuner-->Amplifier-->Analog driver-->||-->Earphones > <----------- Radio -------------------> > > See where the antenna goes? Nope; separation of RF and AF by simple filters. Using the ear bud/head set cord as an antenna is a common practice. -- Jim Pennino
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| From | benj <nobody@gmail.com> |
|---|---|
| Date | 2015-11-17 16:59 -0500 |
| Message-ID | <564ba330$0$31334$c3e8da3$dd9697d2@news.astraweb.com> |
| In reply to | #533828 |
On 11/17/2015 03:28 PM, jimp@specsol.spam.sux.com wrote: > Odd Bodkin <bodkinodd@gmail.com> 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. >> >> Signals-->||-->Tuner-->Amplifier-->Analog driver-->||-->Earphones >> <----------- Radio -------------------> >> >> See where the antenna goes? > > Nope; separation of RF and AF by simple filters. > > Using the ear bud/head set cord as an antenna is a common practice. jimp, Ivory Tower Boinker is as dumb as a stump. He believes everything those in authority tell him and parrots it all over the net. He's worse than Asshat. As you can see from his idiotic "explanation" that he doesn't have a clue even when someone TOLD him where the antenna was he still can't find it. He can't find his own ass even if allowed to use both hands. But he still thinks he knows more than everybody else. When it comes to any practical understanding, Boinker couldn't figure out which end of the soldering iron is the handle even if it were on! As to answer the question, there is much more involved in an antenna than simply length vs signal. You didn't say what kind of radio this was. Frequency can be important. Issues can be standing waves in the room or on the antenna or perhaps the longer wire creating a bad impedance match to the radio. Key issue is how the impedance of a transmission line transforms as you move along it.
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| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Date | 2015-11-18 22:56 +0100 |
| Message-ID | <4736856.kWDMch3Bm0@PointedEars.de> |
| In reply to | #533802 |
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. [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. Radio waves are electromagnetic (EM) waves with frequencies from ca. 3 kHz to 300 GHz. [1] EM waves can be understood as self-propagating waves of self-inducing electric and magnetic fields. [2] An electrical current in an conductor creates a magnetic field (MF) around it (Ørstedt, 1820; see: electromagnet). If it is an oscillating current, the result is an oscillation in the surrounding MF, which induces an oscillating electric field (EF) which creates an oscillating MF and so on, propagating through space: an EM wave. So far for the transmitter, at the radio station. Also, a change in the MF around a conductor, such as a wire, induces a current in it (Faraday, 1831). [3] In particular, with a radio receiver, “when radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor” (Hertz, ca. 1880). [1] AIUI, a conductor serves best as an antenna (either for transmission or reception of radio waves) if its electrical resonance frequency matches approximately the frequency of the radio waves to be received. [4] The electrical resonance frequency f₀ of a conductor is given by the angular frequency ω₀ = 1∕√(LC) where L is the inductance and C is the capacitance of the conductor, and ω₀ = 2πf₀, so that f₀ = ω₀∕2π = 1∕(2π√(LC)). [5] The inductance of a coaxial cable [6a] is L = µ₀l∕2π ln(R₂∕R₁) where µ₀ – vacuum permeability l – length of the cable R₂ – half of the thickness of the cable (also a₁, outer radius) R₁ – half of the thickness of the conductor (also a, inner radius). [6b] The capacitance of a coaxial cable is C = 2πεl∕ln(R₂∕R₁) where additionally ε is (absolute) permittivity (ε = ε_r ε₀, whereas the relative permittivity ε_r depends on the material, and ε₀ is the vacuum permittivity). [7a][7b] So both the inductance and the capacitance of a conductor increase with length, which means that its electrical resonance frequency decreases with length. Or, IOW, since wavelength λ = c∕f, where f is frequency, “Antennae length is proportional to the wavelength of reception.” [0] Therefore, the longer line does _not_ improve reception quality of a particular radio channel (its station transmitting at a particular frequency) to begin with. 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. 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. However, I understand that there are also traveling wave antennae that are nonresonant, like random wire for receiving shortwave radio. [9] 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 ___________ [0] <https://www.quora.com/How-headphones-work-as-an-Antenna-to-play-FM-radio-channels-on-Mobile-phones-Why-mobile-companies-doesnt-install-the-same-inbuilt-Antenna-on-phones-to-be-able-to-play-FM-without-the-headphones> [1] <https://en.wikipedia.org/wiki/Radio> [2] <https://en.wikipedia.org/wiki/Electromagnetic_radiation> [3] <https://en.wikipedia.org/wiki/Electromagnetic_induction> [4] <https://en.wikipedia.org/wiki/Antenna_(radio)#Antenna_types> [5] <https://en.wikipedia.org/wiki/RLC_circuit> [6a] <https://en.wikipedia.org/wiki/Coaxial_cable> [6b] <https://en.wikipedia.org/wiki/Inductance#Self-inductance_of_simple_electrical_circuits_in_air> [7a] <https://en.wikipedia.org/wiki/Capacitance#Capacitance_of_simple_systems> [7b] <https://en.wikipedia.org/wiki/Permittivity> [8] <https://en.wikipedia.org/wiki/Electrical_resistance_and_conductance#Relation_to_resistivity_and_conductivity> [9] <https://en.wikipedia.org/wiki/Antenna_(radio)#Traveling_wave> p. -- Q: How many theoretical physicists specializing in general relativity does it take to change a light bulb? A: Two: one to hold the bulb and one to rotate the universe. (from: WolframAlpha)
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| From | gilber34 <fafa@invalid.com> |
|---|---|
| Date | 2015-11-18 16:57 -0600 |
| Message-ID | <n2ivpn$gh9$1@speranza.aioe.org> |
| In reply to | #533995 |
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. [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. > 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. > 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.) > > However, I understand that there are also traveling wave antennae that are > nonresonant, like random wire for receiving shortwave radio. [9] 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.
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| From | jimp@specsol.spam.sux.com |
|---|---|
| Date | 2015-11-18 23:15 +0000 |
| Message-ID | <fddvhc-vob.ln1@mail.specsol.com> |
| In reply to | #533999 |
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. >> 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. > > >> 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] 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. -- Jim Pennino
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| From | gilber34 <fafa@invalid.com> |
|---|---|
| Date | 2015-11-18 20:42 -0600 |
| Message-ID | <n2jcuf$9qr$1@speranza.aioe.org> |
| In reply to | #534000 |
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. > >>> 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. >>> 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. 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. 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) he said he was listening to FM, so he is in a city, 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)
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| From | jimp@specsol.spam.sux.com |
|---|---|
| Date | 2015-11-19 05:29 +0000 |
| Message-ID | <2a30ic-rud.ln1@mail.specsol.com> |
| In reply to | #534011 |
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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| From | gilber34 <fafa@invalid.com> |
|---|---|
| Date | 2015-11-19 08:54 -0600 |
| Message-ID | <n2knqi$4vu$1@speranza.aioe.org> |
| In reply to | #534017 |
On 11/18/2015 11:29 PM, jimp@specsol.spam.sux.com wrote: > 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: >>>>> >>>>> >>>>> 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. irrelevant also > >>>>> 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. not at all, the typical tradeoff in designing preamps, how much gain, in how much selectivity (bandwidth), how much NF. Typical in the below 30MHz RF preamps is no antenna matching, other factors dominate. > > Mixing requires a non-linear device and preamps are built to be linear > devices. preamps are linear only in a range, outside this range all preamps are mixers. And even in their linear range, they also provide gain to other signals in their bandwidth, which also cause following stages to be over driven, to become mixers. If you put a +20dB preamp on your FM radio, it will trash it out totally. > > Matchins still important to preamps. and so is intentional mis-matching, important to provide stability, and loading for front end filters, and finding best NF, a tradeoff typically. Depends on the band and application. > >> 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. I see you are unfamiliar with FM radio. "Capture" is also closely related to "takeover gain" That is why FM sounds so much better than AM. https://www.physicsforums.com/threads/fm-modulation-capture-effect.747206/ > >> 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. no it is a nice but older 10KHz to 22GHz Unit, easy to fix smoked resistor, but a 100#der almost a boat anker. but Troll on if you must, but you could contribute too.
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| From | jimp@specsol.spam.sux.com |
|---|---|
| Date | 2015-11-19 18:44 +0000 |
| Message-ID | <0th1ic-34j.ln1@mail.specsol.com> |
| In reply to | #534036 |
gilber34 <fafa@invalid.com> wrote: > On 11/18/2015 11:29 PM, jimp@specsol.spam.sux.com wrote: >> 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: >>>>>> > >>>>>> >>>>>> 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. > > irrelevant also Non sequitur. > >> >>>>>> 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. > > not at all, the typical tradeoff in designing preamps, how much gain, in > how much selectivity (bandwidth), how much NF. > Typical in the below 30MHz RF preamps is no antenna matching, other > factors dominate. Nope. > >> >> Mixing requires a non-linear device and preamps are built to be linear >> devices. > > preamps are linear only in a range, outside this range all preamps are > mixers. And even in their linear range, they also provide gain to other > signals in their bandwidth, which also cause following stages to be over > driven, to become mixers. Arm waving. > > If you put a +20dB preamp on your FM radio, it will trash it out totally. This just shows you haven't a clue why one would use a preamp. > >> >> Matchins still important to preamps. > > and so is intentional mis-matching, important to provide stability, and > loading for front end filters, and finding best NF, a tradeoff > typically. Depends on the band and application. Nope. > >> >>> 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. > > I see you are unfamiliar with FM radio. > "Capture" is also closely related to "takeover gain" > That is why FM sounds so much better than AM. Nope. Clueless. FYI, FM sounds better than AM (for broadcast) because the allowed bandwidth is much higher. It has little to nothing to do with the modulation other than FM is static resistant. > https://www.physicsforums.com/threads/fm-modulation-capture-effect.747206/ > >> >>> 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. > > no it is a nice but older 10KHz to 22GHz Unit, easy to fix smoked > resistor, but a 100#der almost a boat anker. > but Troll on if you must, but you could contribute too. OK. Go buy a copy of the Radio Amateurs Handbook and read it. -- Jim Pennino
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| From | gilber34 <fafa@invalid.com> |
|---|---|
| Date | 2015-11-22 15:32 -0600 |
| Message-ID | <n2tc8f$9h$1@speranza.aioe.org> |
| In reply to | #534072 |
On 11/19/2015 12:44 PM, jimp@specsol.spam.sux.com wrote: > gilber34 <fafa@invalid.com> wrote: >> On 11/18/2015 11:29 PM, jimp@specsol.spam.sux.com wrote: >>> 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: <snip> >>>> 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. >> >> not at all, the typical tradeoff in designing preamps, how much gain, in >> how much selectivity (bandwidth), how much NF. >> Typical in the below 30MHz RF preamps is no antenna matching, other >> factors dominate. > > Nope. have to match transmitter, below 30 MHz receiver preamps not much need at all. > >> >>> >>> Mixing requires a non-linear device and preamps are built to be linear >>> devices. >> >> preamps are linear only in a range, outside this range all preamps are >> mixers. And even in their linear range, they also provide gain to other >> signals in their bandwidth, which also cause following stages to be over >> driven, to become mixers. > > Arm waving. this is stuff experienced RF designers know, not the Hams, or amateur radio people what is left of them. > >> >> If you put a +20dB preamp on your FM radio, it will trash it out totally. > > This just shows you haven't a clue why one would use a preamp. > so you are recommending using +20dB preamp for FM radios ? >> >>> >>> Matchins still important to preamps. >> >> and so is intentional mis-matching, important to provide stability, and >> loading for front end filters, and finding best NF, a tradeoff >> typically. Depends on the band and application. > > Nope. well, that is RF design, not amateur radio sandbox tinkering. >>> >>> Most of that is just nonsense. >> >> I see you are unfamiliar with FM radio. >> "Capture" is also closely related to "takeover gain" >> That is why FM sounds so much better than AM. > > Nope. > > Clueless. > > FYI, FM sounds better than AM (for broadcast) because the allowed bandwidth > is much higher. It has little to nothing to do with the modulation other > than FM is static resistant. Why is FM "static resistant" ? Capture effect. Guess you should take some time and refresh yourself. > >> https://www.physicsforums.com/threads/fm-modulation-capture-effect.747206/ >> >>> >>>> 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. >> >> no it is a nice but older 10KHz to 22GHz Unit, easy to fix smoked >> resistor, but a 100#der almost a boat anker. >> but Troll on if you must, but you could contribute too. > > OK. > > Go buy a copy of the Radio Amateurs Handbook and read it. > that is for Amateurs, 1960's stuff, and didn't they quit printing that a while back ?
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| From | jimp@specsol.spam.sux.com |
|---|---|
| Date | 2015-11-22 23:16 +0000 |
| Message-ID | <6vu9ic-bgi.ln1@mail.specsol.com> |
| In reply to | #534613 |
gilber34 <fafa@invalid.com> wrote: > On 11/19/2015 12:44 PM, jimp@specsol.spam.sux.com wrote: >> gilber34 <fafa@invalid.com> wrote: >>> On 11/18/2015 11:29 PM, jimp@specsol.spam.sux.com wrote: >>>> 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: > <snip> > >>>>> 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. >>> >>> not at all, the typical tradeoff in designing preamps, how much gain, in >>> how much selectivity (bandwidth), how much NF. >>> Typical in the below 30MHz RF preamps is no antenna matching, other >>> factors dominate. >> >> Nope. > > have to match transmitter, below 30 MHz receiver preamps not much need > at all. Preamps have nothing to do with transmitters. A switchable preamp is very handy; switch in it when signal levels are low and out when there are strong signals that would cause overload. >>>> >>>> Mixing requires a non-linear device and preamps are built to be linear >>>> devices. >>> >>> preamps are linear only in a range, outside this range all preamps are >>> mixers. And even in their linear range, they also provide gain to other >>> signals in their bandwidth, which also cause following stages to be over >>> driven, to become mixers. >> >> Arm waving. > > this is stuff experienced RF designers know, not the Hams, or amateur > radio people what is left of them. This is very basic RF that you can find in the Radio Amateurs Handbook. I suggest you read it. >>> >>> If you put a +20dB preamp on your FM radio, it will trash it out totally. >> >> This just shows you haven't a clue why one would use a preamp. >> > > so you are recommending using +20dB preamp for FM radios ? No, I am saying you don't know what you are talking about. >>>> Matchins still important to preamps. >>> >>> and so is intentional mis-matching, important to provide stability, and >>> loading for front end filters, and finding best NF, a tradeoff >>> typically. Depends on the band and application. >> >> Nope. > > well, that is RF design, not amateur radio sandbox tinkering. Nope, it is babbling word salad. >>>> >>>> Most of that is just nonsense. >>> >>> I see you are unfamiliar with FM radio. >>> "Capture" is also closely related to "takeover gain" >>> That is why FM sounds so much better than AM. >> >> Nope. >> >> Clueless. >> >> FYI, FM sounds better than AM (for broadcast) because the allowed bandwidth >> is much higher. It has little to nothing to do with the modulation other >> than FM is static resistant. > > Why is FM "static resistant" ? Capture effect. Nope, it is because static is primarily AM. > Guess you should take some time and refresh yourself. Guess you still haven't a clue what you are talking about. >> >>> https://www.physicsforums.com/threads/fm-modulation-capture-effect.747206/ >>> >>>> >>>>> 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. >>> >>> no it is a nice but older 10KHz to 22GHz Unit, easy to fix smoked >>> resistor, but a 100#der almost a boat anker. >>> but Troll on if you must, but you could contribute too. >> >> OK. >> >> Go buy a copy of the Radio Amateurs Handbook and read it. >> > > that is for Amateurs, 1960's stuff, and didn't they quit printing that > a while back ? Nope, it is kept up to date and is far above your demonstrated technical level. -- Jim Pennino
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| From | HVAC <mr.hvac@gmail.com> |
|---|---|
| Date | 2015-11-19 06:59 -0800 |
| Message-ID | <12032439-67df-4b3c-9f8b-0680e74f0efc@googlegroups.com> |
| In reply to | #534011 |
Smoke comes out a lot easier than it goes back in
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| From | benj <none@gmail.com> |
|---|---|
| Date | 2015-11-19 20:02 -0500 |
| Message-ID | <jiu3y.143082$1Z.99845@fx01.iad> |
| In reply to | #534038 |
On 11/19/2015 09:59 AM, HVAC wrote:
> Smoke comes out a lot easier than it goes back in
A concise statement of HVAC's level of technical and scientific
understanding of radio. (And most other toptics)
Aren't you glad we have such a compendium of electromagnetic expertise
for Moderator of this physics newsgroup?
--
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| From | benj <none@gmail.com> |
|---|---|
| Date | 2015-11-19 01:36 -0500 |
| Message-ID | <w5e3y.137768$fC2.51232@fx03.iad> |
| In reply to | #533995 |
On 11/18/2015 04:56 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.
This is typical of Boinker. HE babbles on and on parroting what he
thinks authorities have told him without any understanding at all.
> As the OP indicated, earphone (also: headphone) cords contain wires
> which can serve as antennas. [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. Radio waves are
> electromagnetic (EM) waves with frequencies from ca. 3 kHz to 300
> GHz. [1] EM waves can be understood as self-propagating waves of
> self-inducing electric and magnetic fields. [2]
Actually this is wrong. But wikipedia editors perpetuate the censorship
of actual effects. Wikipedia is not any reliable source. They are as
political as any media.
> An electrical current in an conductor creates a magnetic field (MF)
> around it (Ørstedt, 1820; see: electromagnet). If it is an
> oscillating current, the result is an oscillation in the surrounding
> MF, which induces an oscillating electric field (EF) which creates an
> oscillating MF and so on, propagating through space: an EM wave. So
> far for the transmitter, at the radio station.
No. Magnetic and Electric fields are created together and propagate
together. They do not "create" each other.
> Also, a change in the MF around a conductor, such as a wire, induces
> a current in it (Faraday, 1831). [3] In particular, with a radio
> receiver, “when radio waves strike an electrical conductor, the
> oscillating fields induce an alternating current in the conductor”
> (Hertz, ca. 1880). [1]
This is wrong too. Faraday's law is bogus. (Except for the way Faraday
actually stated it)
> AIUI, a conductor serves best as an antenna (either for transmission
> or reception of radio waves) if its electrical resonance frequency
> matches approximately the frequency of the radio waves to be
> received. [4]
Well, yes, but it's not because of it's ability to collect radio waves.
It's because of matching to an output load. Generally speaking
collection of waves is determined by a parameter called "aperture" which
oddly enough IS related to the length of the antenna and its size in
general. But increasing the size of an antenna does not always increase
the aperture.
> The electrical resonance frequency f₀ of a conductor is given by the
> angular frequency
>
> ω₀ = 1∕√(LC)
>
> where L is the inductance and C is the capacitance of the conductor,
> and
>
> ω₀ = 2πf₀,
>
> so that
>
> f₀ = ω₀∕2π = 1∕(2π√(LC)). [5]
>
> The inductance of a coaxial cable [6a] is
>
> L = µ₀l∕2π ln(R₂∕R₁)
>
> where
>
> µ₀ – vacuum permeability l – length of the cable R₂ – half of the
> thickness of the cable (also a₁, outer radius) R₁ – half of the
> thickness of the conductor (also a, inner radius). [6b]
>
> The capacitance of a coaxial cable is
>
> C = 2πεl∕ln(R₂∕R₁)
>
> where additionally ε is (absolute) permittivity (ε = ε_r ε₀, whereas
> the relative permittivity ε_r depends on the material, and ε₀ is the
> vacuum permittivity). [7a][7b]
>
> So both the inductance and the capacitance of a conductor increase
> with length, which means that its electrical resonance frequency
> decreases with length. Or, IOW, since wavelength λ = c∕f, where f is
> frequency, “Antennae length is proportional to the wavelength of
> reception.” [0] Therefore, the longer line does _not_ improve
> reception quality of a particular radio channel (its station
> transmitting at a particular frequency) to begin with.
Technobabble.
Shows what happens when mathematics is blindly applied with no
understanding!
> 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. 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.
Technobabble.
> However, I understand that there are also traveling wave antennae
> that are nonresonant, like random wire for receiving shortwave radio.
> [9] 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.
Antennas (antennae are on bugs) have been studied and developed for more
than a century and the complexities are quite known. To make
speculations with no information (OP didn't even say what band he was
listening to) isn't productive. With some information perhaps a
simplified "explanation" could be generated.
Depending on frequency, a number of factors could come into play. One
might be the wavelength of the antenna. Note that if an antenna is a
full wavelength long half of it has one phase and the other the opposite
phase so it cancels. Hence If the antenna were half wave and you
extended it to full wave output would go DOWN not up. None of this
information is available. Another case is that the the antenna may be
working fine but changing the length changes the output impedance which
changes the matching into the radio. The bad match reflects power and
signal goes down. And Thirdly, the whole situation is so ill-defined
that little can be said. For example if wavelengths are short (FM band)
There can be standing waves in room which a longer antenna can interact
with in a negative way. (Remember the old TV days when someone had to
stand on one foot and touch the window blinds so the program could be seen?)
Basically antennas that are earphone wires or line cord antennas are
really not able to be precisely described by theory because of the lack
of defined circumstances. They are added to products as just kind of
"here's something even if it is crap" feature. You are WAY over-thinking
the problem!
> PointedEars ___________ [0]
> <https://www.quora.com/How-headphones-work-as-an-Antenna-to-play-FM-radio-channels-on-Mobile-phones-Why-mobile-companies-doesnt-install-the-same-inbuilt-Antenna-on-phones-to-be-able-to-play-FM-without-the-headphones>
>
>
[1] <https://en.wikipedia.org/wiki/Radio>
> [2] <https://en.wikipedia.org/wiki/Electromagnetic_radiation> [3]
> <https://en.wikipedia.org/wiki/Electromagnetic_induction> [4]
> <https://en.wikipedia.org/wiki/Antenna_(radio)#Antenna_types> [5]
> <https://en.wikipedia.org/wiki/RLC_circuit> [6a]
> <https://en.wikipedia.org/wiki/Coaxial_cable> [6b]
> <https://en.wikipedia.org/wiki/Inductance#Self-inductance_of_simple_electrical_circuits_in_air>
>
>
[7a]
> <https://en.wikipedia.org/wiki/Capacitance#Capacitance_of_simple_systems>
>
>
[7b] <https://en.wikipedia.org/wiki/Permittivity>
> [8]
> <https://en.wikipedia.org/wiki/Electrical_resistance_and_conductance#Relation_to_resistivity_and_conductivity>
>
>
[9] <https://en.wikipedia.org/wiki/Antenna_(radio)#Traveling_wave> p.
>
--
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\:\~\:\/:/ / \:\~\:\ \/__/ \/__|:|/:/ / \::/ /
\:\ \::/ / \:\ \:\__\ |:/:/ / \/__/
\:\/:/ / \:\ \/__/ |::/ /
\::/__/ \:\__\ /:/ /
~~ \/__/ \/__/
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| From | gilber34 <fafa@invalid.com> |
|---|---|
| Date | 2015-11-17 13:28 -0600 |
| Message-ID | <n2fv51$t4f$1@speranza.aioe.org> |
| In reply to | #533801 |
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? > > -- > Rich > if antenna too long/large in FM band, the other strong FM channels can break through the selectivity and sound like noise, or chunky noise. In the industry it is called de-sence. Most FM radios are cheaply build now, and have poor selectivity (RF and/or IF filtering), so most sound like crap. You may find a length that works best for your station. Too short not enough signal, too long, the big FM stations bomb through your cheap FM radio's selectivity. It is not physics, it is RF engineering. Also the antennas on FM Radios use a wire, and part of the circuit board, which will include your headphones. walkie talkies use part of your arm as a radiating structure, and cellphones will too to a lesser degree.
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| From | "reber g=emc^2" <herbertglazier0@gmail.com> |
|---|---|
| Date | 2015-11-17 14:04 -0800 |
| Message-ID | <6b5f8c35-7374-4502-ad9d-ea3431b913cd@googlegroups.com> |
| In reply to | #533801 |
On Tuesday, November 17, 2015 at 10:42:09 AM UTC-8, 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? > > -- > Rich Car antenna 3 feet,and that is the length of radio wave sent out.Making it bigger than the incoming wave does not help.Get the picture trebert
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| From | jimp@specsol.spam.sux.com |
|---|---|
| Date | 2015-11-17 22:35 +0000 |
| Message-ID | <3nmshc-1o2.ln1@mail.specsol.com> |
| In reply to | #533845 |
reber g=emc^2 <herbertglazier0@gmail.com> wrote: > On Tuesday, November 17, 2015 at 10:42:09 AM UTC-8, 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? >> >> -- >> Rich > > Car antenna 3 feet,and that is the length of radio wave sent out.Making it bigger than the incoming wave does not help.Get the picture trebert Nope; the quarter wave length of the signal is about 90 feet for AM and about 2.4 feet for FM. -- Jim Pennino
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