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Groups > sci.physics > #536556
| From | jimp@specsol.spam.sux.com |
|---|---|
| Newsgroups | sci.physics |
| Subject | Re: long antenna |
| Date | 2015-11-30 20:48 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <o9puic-at8.ln1@mail.specsol.com> (permalink) |
| References | (9 earlier) <n3dala$v0i$1@speranza.aioe.org> <16opic-5al.ln1@mail.specsol.com> <n3hjv2$kku$1@speranza.aioe.org> <s0juic-u98.ln1@mail.specsol.com> <ne27y.260460$eP.96568@fx13.iad> |
benj <none@gmail.com> wrote: > On 11/30/2015 02:01 PM, jimp@specsol.spam.sux.com wrote: >> gilber34 <fafa@invalid.com> wrote: >>> On 11/28/2015 4:58 PM, jimp@specsol.spam.sux.com wrote: >>>> gilber34 <fafa@invalid.com> wrote: >>>>> On 11/27/2015 10:46 AM, benj wrote: >>>>>> On 11/27/2015 02:01 AM, gilber34 wrote: >>>>>>> On 11/26/2015 10:45 PM, benj wrote: >>>>>>>> On 11/26/2015 08:37 PM, jimp@specsol.spam.sux.com wrote: >>>>> >>>>>> >>>>>> perhaps not gamma ray, but you DO know that X-ray parabolic antennas >>>>>> exist, right? >>>>> >>>>> using glancing, paraboioids and hyperboioids, not quite the same as a >>>>> dish. but my point was to counter the over generalization that EM >>>>> frequency being the same. Still waiting on the size of the 60 HZ dish >>>>> for 20 dB gain... >>>> >>>> Pretty large, but the physical size is irrelevant; the gain of a dish >>>> is a function of it's diameter in wavelengths, so the gain of a 3 lambda >>>> 60 Hz dish is the same as the gain of a 3 lambda 60 GHz dish. >>> >>> as usual, WRONG. >> >> Nope. >> >> Then why do antenna books have nomographs of dB gain verssus physical >> size with straight lines for frequency. >> >>> the 60Hz dish would be 17,794,063.6 meters wide or 11,056 miles wide or >>> 100 times the diameter of the Earth. Impossable to build it at all. >> >> Not in space given enough time and money. >> >>> THE PHYSICAL SIZE IS THE ISSUE ! >> >> Nope. >> >> Physical size only determines the econonomic practicably, not the RF >> characteristics. >> >>> (what size waveguide do you feed a 60 Hz dish with ?) >> >> You assume due to your utter ignorance of antennas and RF in general >> that all dishes are fed with waveguide; they are not. It is very >> common to feed dishes in the lower microwave region and below with >> coax. >> >>> your max surface roughness at 60GHz is what ? >> >> It is perfect because competant people were used to build it and >> irrelevant to the fact that antennas scale in frequency. >> >>> How much beam taper do you illuminate the edges with to avoid backlobes >>> at 60GHz? which would pick up the 60HZ earth very well. What would the >>> F/B ratio be to pick up a 60Hz craft 1,000,000,000 miles out ? >> >> The same as at 60 GHz. >> >>>> The only issue with a dish at gamma or X-ray frquencies is that the >>>> dish has to be made of a material that is reflective at those frequencies, >>> >>> which there are not any for a parabolic dish. >> >> Which is irrelevant to the fact that antennas scale in frequency. >> >> If you can find a material that is relective at gamma or X-ray frquencies, >> then such a dish will perform just the same as any other dish at any >> other frequency with the same diameter in wavelengths. >> >>> what is the max surface roughness you could have ? (hint: 1/4 lamda and >>> how much is that?) can anybody do that yet ? >>> so you are WRONG again, find the answer in ARRL, not. >> >> The requirements would be the same as any other dish at any other frequency >> with the same diameter in wavelengths. >> >> The thing you are utterly unable to understand is that electromagnetic >> theory of antennas is frequency independant. >> >> The practical ability to construct a given antenna may change with >> frequency, but the electromagnetic theory does NOT. > > Exactly correct. And in fact X-ray antennas have been built and used! > They are very interesting practical physics. > As jimp said the theory works exactly the same as at any frequency! > > The trick with X-ray antennas is to get reflectivity and achieve the > accuracy of figure at the given wavelength. > > The first was done very cleverly by not trying to come into a dish > perpendicularly like a typical dish antenna or optical mirror, but > building a very low off-axis parabola so the radiation comes in at a > very low angle. Things that are not so reflective straight-on become > very shiny at low angles! Cute! > > And as for accuracy, well that just means that one must use modern > techniques VERY carefully and you can get some passable results even at > x-ray wavelengths. I wonder how much babbling nonsense he would generate if I were to bring up dielectric lens antennas, which work exactly like a magnifying glass given he has already said RF does not work like light and magnifying glasses? -- 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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