On Aug 26, 9:11�am, "Symon" <symon_bre...@hotmail.com> wrote:> "Randy Yates" <ya...@ieee.org> wrote in message > > news:m3y6p6vk78.fsf@ieee.org... > > > Omni is well-defined: equal in all directions. This is the gist of the > > issue. If we marketing redefines terms, we no longer know what they're > > really saying. > > Sadly, it's not well defined when refering to antennas. FWIW, An > omnidirectional antenna is usually defined as meaning one that radiates > equally in all directions in a plane. I guess that's because an antenna that > radiates equally in all three dimensional directions is impossible to make, > as proven by the hairy ball theorem. Really! > HTH., Syms.yep radio engineers usually take: OMNI to mean radiates equall well in all directions OF THE COMPASS i.e 360 deg in the plane toward the horizon... and they will use the term ISOTROIC to mean radiates equally well in ALL directions azimuth and elevation... Mark
High Gain *Omni* Antenna?!?
Started by ●August 25, 2009
Reply by ●August 26, 20092009-08-26
Reply by ●August 26, 20092009-08-26
On 8/26/2009 5:24 AM, Randy Yates wrote:> glen herrmannsfeldt<gah@ugcs.caltech.edu> writes: > >> Randy Yates<yates@ieee.org> wrote: >> (regarding the subject: High Gain *Omni* Antenna?!?) >> >> < How is this possible? Or is it a new level of marketing-speak? >> >> Well, omni might mean just in the plane parallel to the ground. > > Uhuh. Then it ain't omni.As others have pointed out, by the general use of the term, it could still be omni in the horizontal plane. For the most part, antenna patterns are published with respect to azimuth, so the vertical pattern isn't even a consideration in many (if not most) applications. So when somebody says "omni", they generally mean in the horizontal plain. Also as has been pointed out, if you want an antenna with a reasonably spherical radiation contour, the word more applicable there is "isotropic". I think their mistake is mixing "omni" and "directional", i.e., "7 dBi High Gain Directional Antenna". Usually "directional" is also taken in the azimuth direction, or, for really directive antennas, wrt boresight, which implies not even anything close to an omni azimuth pattern. FWIW, this sort of thing isn't unusual at all in comm. It's not anything close to as wacky as the audio and consumer markets see, but one has to take most definitions as fairly soft. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
Reply by ●August 26, 20092009-08-26
"Symon" <symon_brewer@hotmail.com> writes:> "Randy Yates" <yates@ieee.org> wrote in message > news:m3y6p6vk78.fsf@ieee.org... >> >> Omni is well-defined: equal in all directions. This is the gist of the >> issue. If we marketing redefines terms, we no longer know what they're >> really saying. >> > Sadly, it's not well defined when refering to antennas. FWIW, An > omnidirectional antenna is usually defined as meaning one that radiates > equally in all directions in a plane.Hey Symon, Hmm. I checked a couple of sources, e.g., the ARRL Antenna Handbook, and it appears you're right.> I guess that's because an antenna that radiates equally in all three > dimensional directions is impossible to make, as proven by the hairy > ball theorem. Really!Truth is stranger than fiction! -- Randy Yates % "Rollin' and riding and slippin' and Digital Signal Labs % sliding, it's magic." mailto://yates@ieee.org % http://www.digitalsignallabs.com % 'Living' Thing', *A New World Record*, ELO
Reply by ●August 27, 20092009-08-27
Eric Jacobsen <eric.jacobsen@ieee.org> writes:> On 8/26/2009 5:24 AM, Randy Yates wrote: >> glen herrmannsfeldt<gah@ugcs.caltech.edu> writes: >> >>> Randy Yates<yates@ieee.org> wrote: >>> (regarding the subject: High Gain *Omni* Antenna?!?) >>> >>> < How is this possible? Or is it a new level of marketing-speak? >>> >>> Well, omni might mean just in the plane parallel to the ground. >> >> Uhuh. Then it ain't omni. > > As others have pointed out, by the general use of the term, it could > still be omni in the horizontal plane. For the most part, antenna > patterns are published with respect to azimuth, so the vertical > pattern isn't even a consideration in many (if not most) applications. > So when somebody says "omni", they generally mean in the horizontal > plain.Or fancy. Sorry. Yes, I stand (sit, type, etc.) corrected.> [...] > I think their mistake is mixing "omni" and "directional", i.e., "7 dBi > High Gain Directional Antenna".Well, herein was my problem with using omni in the manner you described above; omni *is* (in a sense) directional. So (in a sense) their terminology is correct from that POV.> Usually "directional" is also taken in the azimuth direction, or, for > really directive antennas, wrt boresight, which implies not even > anything close to an omni azimuth pattern.Too many "usually"ies.> FWIW, this sort of thing isn't unusual at all in comm. It's not > anything close to as wacky as the audio and consumer markets see, but > one has to take most definitions as fairly soft.Thus the meaning is also correspondingly ambiguous. -- Randy Yates % "And all that I can do Digital Signal Labs % is say I'm sorry, mailto://yates@ieee.org % that's the way it goes..." http://www.digitalsignallabs.com % Getting To The Point', *Balance of Power*, ELO
Reply by ●August 27, 20092009-08-27
On 8/27/2009 4:34 AM, Randy Yates wrote:> Eric Jacobsen<eric.jacobsen@ieee.org> writes: > >> On 8/26/2009 5:24 AM, Randy Yates wrote: >>> glen herrmannsfeldt<gah@ugcs.caltech.edu> writes: >>> >>>> Randy Yates<yates@ieee.org> wrote: >>>> (regarding the subject: High Gain *Omni* Antenna?!?) >>>> >>>> < How is this possible? Or is it a new level of marketing-speak? >>>> >>>> Well, omni might mean just in the plane parallel to the ground. >>> Uhuh. Then it ain't omni. >> As others have pointed out, by the general use of the term, it could >> still be omni in the horizontal plane. For the most part, antenna >> patterns are published with respect to azimuth, so the vertical >> pattern isn't even a consideration in many (if not most) applications. >> So when somebody says "omni", they generally mean in the horizontal >> plain. > > Or fancy. > > Sorry. Yes, I stand (sit, type, etc.) corrected. > >> [...] >> I think their mistake is mixing "omni" and "directional", i.e., "7 dBi >> High Gain Directional Antenna". > > Well, herein was my problem with using omni in the manner you described > above; omni *is* (in a sense) directional. So (in a sense) their > terminology is correct from that POV. > >> Usually "directional" is also taken in the azimuth direction, or, for >> really directive antennas, wrt boresight, which implies not even >> anything close to an omni azimuth pattern. > > Too many "usually"ies. > >> FWIW, this sort of thing isn't unusual at all in comm. It's not >> anything close to as wacky as the audio and consumer markets see, but >> one has to take most definitions as fairly soft. > > Thus the meaning is also correspondingly ambiguous.Yup, and since marketers write the copy it'll probably be that way always and forever. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
Reply by ●August 27, 20092009-08-27
On Aug 27, 12:26=A0pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:> > Yup, and since marketers write the copy it'll probably be that way > always and forever. >Some years ago, I remember an advertisement for a rabbit-ears antenna for TVs which claimed "Never pay for cable again! Amazing new invention pulls TV signals right out of the air. Now you can watch your favorite shows for free! No monthly payments, no hassle, no outages, and no one can ever cut off your free TV service." ...and you know what? I bought it and much to my surprise, the dang thing worked perfectly; that is, until a couple of months ago, when it stopped working completely. One day, everything was fine, and the next day, boom! Nothing, nada, zip! no free TV anymore. Some of my friends say that the Federal government pulled the plug on my free TV, but they are Republicans and will blame the Obama administration for anything. I think my TV antenna just needs fixing. Unfortunately, the warranty on my antenna expired a long time ago and the company that sold it to me is out of business anyway. Does anyone know of a place that might be able to repair the antenna for me? --Dilip Tongueincheek
Reply by ●August 27, 20092009-08-27
On 27 Aug, 20:16, "dvsarw...@yahoo.com" <dvsarw...@gmail.com> wrote:> I think my TV antenna just needs fixing. =A0Unfortunately, > the warranty on my antenna expired a long time ago > and the company that sold it to me is out of business > anyway. =A0Does anyone know of a place that might be > able to repair the antenna for me?You might want to check if there has been a change in transmissions. Over here, the old-style analog TV transmitters have gone digital over the past couple of years. So one needs some decoder thingy in addition to the antenna, to get access to the transmissions. And of course, those decoder thingys are not free. Rune
Reply by ●August 27, 20092009-08-27
Rune Allnor wrote:> On 27 Aug, 20:16, "dvsarw...@yahoo.com" <dvsarw...@gmail.com> wrote: > > >>I think my TV antenna just needs fixing. Unfortunately, >>the warranty on my antenna expired a long time ago >>and the company that sold it to me is out of business >>anyway. Does anyone know of a place that might be >>able to repair the antenna for me? > > > You might want to check if there has been a change in > transmissions.Change in transmissions, huh. Nothing seemed to change over the past 30 years; they keep broadcasting the same utter nonsense.> Over here, the old-style analog TV > transmitters have gone digital over the past couple > of years.Even if they will convert to psi-wave radiation, it is not a reason to watch the crap.> So one needs some decoder thingy in addition > to the antenna, to get access to the transmissions. > And of course, those decoder thingys are not free.Sure. It is not enough just to sign up for lobotomy. You have to pay for it as well. BTW, in quite many practical cases it would be desirable to have the high antenna gain but without the corresponding directional properties. Perhaps, MIMO the only way to accomplish that. VLV
Reply by ●August 27, 20092009-08-27
dvsarwate@yahoo.com <dvsarwate@gmail.com> wrote: (snip) < Some years ago, I remember an advertisement for a rabbit-ears < antenna for TVs which claimed < "Never pay for cable again! Amazing new invention < pulls TV signals right out of the air. Now you can < watch your favorite shows for free! No monthly < payments, no hassle, no outages, and no one can < ever cut off your free TV service." If it is the ones I remember ads for, I believe it is just a capacitor from the power line to the antenna output. The ads say something like "turns your whole house into an antenna." The plastic is much bigger to make it look like you get more. Then sometime later, the added the capacitor to TVs with a little wire coming out near the antenna terminals. -- glen
Reply by ●August 27, 20092009-08-27
glen herrmannsfeldt wrote:> dvsarwate@yahoo.com <dvsarwate@gmail.com> wrote: > (snip) > > < Some years ago, I remember an advertisement for a rabbit-ears > < antenna for TVs which claimed > > < "Never pay for cable again! Amazing new invention > < pulls TV signals right out of the air. Now you can > < watch your favorite shows for free! No monthly > < payments, no hassle, no outages, and no one can > < ever cut off your free TV service." > > If it is the ones I remember ads for, I believe it is just > a capacitor from the power line to the antenna output. > The ads say something like "turns your whole house into an antenna." > > The plastic is much bigger to make it look like you get more. > Then sometime later, the added the capacitor to TVs with a little > wire coming out near the antenna terminals.Which of the respondents missed the change from Sarawate to Tongueincheek? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
