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glass-mount omnidirectional antenna?
I used to have a in-car cell phone system and it had a glass-mount
antenna which didn't require drilling. Basically, there was coax(conntected to the cell) to a plate that stuck to the inside of the rear window. Then on the outside of that window was another plate with the antenna attached to it. You can buy these a radio shack I noticed. I've also seem the same done for XM/Sirius Satellite radio. I have searched and searched and so far have not found the same thing for 2.4 ghz wifi. Does anyone know where I can find one? If not, could it be as simple as removing the cell antenna from the exterior plate(of the radio shack cellular version) and reattaching a 2.4 ghz omni? Or maybe I could modify the existing cell antenna to the correct 1/2 wavelength of 2.4ghz? Your suggestions / help / tips are appreciated. -Kevin |
glass-mount omnidirectional antenna?
On 10 Jan 2006 20:01:17 -0800, "kevincw01" wrote:
I used to have a in-car cell phone system and it had a glass-mount antenna which didn't require drilling. Basically, there was coax(conntected to the cell) to a plate that stuck to the inside of the rear window. Then on the outside of that window was another plate with the antenna attached to it. You can buy these a radio shack I noticed. I've also seem the same done for XM/Sirius Satellite radio. I have searched and searched and so far have not found the same thing for 2.4 ghz wifi. Does anyone know where I can find one? If not, could it be as simple as removing the cell antenna from the exterior plate(of the radio shack cellular version) and reattaching a 2.4 ghz omni? Or maybe I could modify the existing cell antenna to the correct 1/2 wavelength of 2.4ghz? Haven't seen a 2.4G unit, which doesn't mean they aren't out there. But the through-glass coupling is fairly narrowband and incorporates tuning elements. The 800/900 MHz units would present a shocking SWR at 2.4G. |
glass-mount omnidirectional antenna?
sorry to have to ask but what is SWR? My guess is sound to [somthing]
ratio? |
glass-mount omnidirectional antenna?
On 10 Jan 2006 23:57:15 -0800, "kevincw01" wrote:
sorry to have to ask but what is SWR? My guess is sound to [somthing] ratio? Standing wave ratio. It is a measure of how well (in this case) the antenna system accepts the energy sent to it up the transmission line and radiates it, compared to reflecting it back to the source transmitter. The transmission line should be 50 ohm coax in your case. If the tranmission line/system has serious impedance variation or discontinuity, power is reflected back to the source rather than passing along the line. As the through-glass coupling system employs frequency-sensitive tuned circuit elements, a substantial change in frequency as you suggest will certainly create a serious impedance discontinuity. Overall transmission efficiency pooter- antenna would be very poor as a result. You may well find that a decent 2.4G antenna on the pooter inside the vehicle is more efficient. |
glass-mount omnidirectional antenna?
looks like i will have to go that route then since I have (so far) not
come across anything for the 2.4G frequency. Either that or drill a whole in the vehicle. |
glass-mount omnidirectional antenna?
In article .com,
says... sorry to have to ask but what is SWR? My guess is sound to [somthing] ratio? Oh dear... Someone didn't pay attention in license class... SWR = Standing Wave Ratio. Put simply, it has to do with how good of a load the antenna presents to the transmitter, and how efficiently it will couple the transmitter's energy to the atmosphere. It needs to be as close to 1:1 as possible. If you're using a wattmeter to measure things, you want to see as low as possible a reading in the 'reflected' mode and as high as possible in the 'forward' mode. Here are some more details. http://www.hamquick.com/tutorial_index.php?id=20 Happy tweaking. -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. (Known to some as Bruce Lane, ARS KC7GR, kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com "If Salvador Dali had owned a computer, would it have been equipped with surreal ports?" |
glass-mount omnidirectional antenna?
i have an excused, i dont have a license :)
|
glass-mount omnidirectional antenna?
On Wed, 11 Jan 2006 22:33:28 -0800, Dr. Anton T. Squeegee
wrote: In article .com, says... sorry to have to ask but what is SWR? My guess is sound to [somthing] ratio? Oh dear... Someone didn't pay attention in license class... SWR = Standing Wave Ratio. Put simply, it has to do with how good of a load the antenna presents to the transmitter, and how efficiently it will couple the transmitter's energy to the atmosphere. Nothing to do with coupling the Tx energy to the "atmosphere". Terminating the line in a resistor of the line's charactertistic impedance will present a nice SWR and radiate very little. |
glass-mount omnidirectional antenna?
"Dr. Anton T. Squeegee" wrote in message
... If you're serious about decent peformance, stay away from glass mount antennas for anything other than receive-only. They're worse than useless for transmitting. I think you better stick to the paintings. Anecdotal evidence is worse than no evidence. Just because one manufacturer's antenna was junk doesn't mean they all are. There does seem to be considerable variability in glass mount antennas, though. Some people report good results, others horrible, and little in the middle. Still, at 2.4G I'd personally be a bit suspicious of glass mount. However, OP has another problem. Nobody has mentioned feedline loss. The wire carrying the signal to the antenna, even with a good SWR, can be a real source of loss, especially at 2.4G. Cable which has a low loss at that frequency is available, but it is expensive and hard to get. As someone else has suggested, it may be better just to keep the antenna in the vehicle. I would also caution OP, presuming he is in the U.S., there are pretty significant limitations to what he can do legally with WiFi. Besides power limitations, there are a number of other limitations designed to protect other users of that spectrum (including amateurs). WiFi is a tertiary user of that spectrum, and you are REQUIRED not to interfere with the other users. You are also required to accept interference from the primary and secondary users. Now the odds that you will be called on interference either way are pretty small, but recognize that in general modifications, even something as simple as an external antenna, are disallowed by the regulations. ... |
glass-mount omnidirectional antenna?
In article . com,
says... i have an excused, i dont have a license :) Well, hurry up and get one then, silly person! Quick, now! Run and pick up a copy of the ARRL's "Now You're Talking!" or I shall have to taunt you again! Seriously, hamateur radio's a fun hobby, and it gives you an excuse to learn all kinds of neat things about electronics in general, and how it applies to radio in particular. Keep the peace(es). -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. (Known to some as Bruce Lane, ARS KC7GR, kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com "If Salvador Dali had owned a computer, would it have been equipped with surreal ports?" |
glass-mount omnidirectional antenna?
In article ,
says... Nothing to do with coupling the Tx energy to the "atmosphere". Terminating the line in a resistor of the line's charactertistic impedance will present a nice SWR and radiate very little. I beg to differ, and I would invite you to think further on this topic. An antenna is a coupling device. Its purpose is to efficiently "couple" or radiate your signal into another transmission medium (open space, including our atmosphere). The antenna (effectively an inductor) needs to be resonant at your operating frequency of choice. It seems to me that the density and composition of the transmission medium you're coupling to has an effect on any antenna's resonant frequency. This, to my understanding, means that an antenna designed for use in open air will not work underwater, nor will, say, a VLF antenna designed for submarine usage work in open air. If you believe I'm misunderstanding, then please point me to some documentation on the subject, and I will cheerfully STFU. Keep the peace(es). -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. (Known to some as Bruce Lane, ARS KC7GR, kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com "If Salvador Dali had owned a computer, would it have been equipped with surreal ports?" |
glass-mount omnidirectional antenna?
In article ,
says... "Dr. Anton T. Squeegee" wrote in message ... If you're serious about decent peformance, stay away from glass mount antennas for anything other than receive-only. They're worse than useless for transmitting. I think you better stick to the paintings. Anecdotal evidence is worse than no evidence. Just because one manufacturer's antenna was junk doesn't mean I'm sorry you feel that way. You know nothing about me, nor my work environment, nor how MANY undercover cars have had issues with glass mounts. This didn't just happen on one vehicle. It was on several. And my own personal experience with glass mounts (yes, I tried using them at one time myself) was terrible. The big problem with glass mounts is their lack of a decent ground plane. They spew RF all over the interior of the vehicle they're being used on, hence the interference that I and others have experienced. Perhaps you're the one who had best stick to "painting." -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. (Known to some as Bruce Lane, ARS KC7GR, kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com "If Salvador Dali had owned a computer, would it have been equipped with surreal ports?" |
glass-mount omnidirectional antenna?
On Thu, 12 Jan 2006 19:13:22 -0800, Dr. Anton T. Squeegee
wrote: In article , says... "Dr. Anton T. Squeegee" wrote in message ... If you're serious about decent peformance, stay away from glass mount antennas for anything other than receive-only. They're worse than useless for transmitting. I think you better stick to the paintings. Anecdotal evidence is worse than no evidence. Just because one manufacturer's antenna was junk doesn't mean I'm sorry you feel that way. You know nothing about me, nor my work environment, nor how MANY undercover cars have had issues with glass mounts. This didn't just happen on one vehicle. It was on several. And my own personal experience with glass mounts (yes, I tried using them at one time myself) was terrible. The big problem with glass mounts is their lack of a decent ground plane. They spew RF all over the interior of the vehicle they're being used on, hence the interference that I and others have experienced. Perhaps you're the one who had best stick to "painting." Just curious. Do you recall how much the windows were tinted? I suspect one of the many reasons for problems is the tinting medium in/on the glass. |
glass-mount omnidirectional antenna?
Dr. Anton T. Squeegee wrote:
. . . An antenna is a coupling device. Its purpose is to efficiently "couple" or radiate your signal into another transmission medium (open space, including our atmosphere). Not really. The power going into the antenna isn't a "signal", but the power leaving it is. An antenna is a transducer -- it changes power in the form of electrical voltages and currents into electromagnetic E and H fields. The antenna (effectively an inductor) needs to be resonant at your operating frequency of choice. That's completely untrue. There's nothing magical about resonance, and a resonant antenna radiates no better or worse than a non-resonant one. As for being an inductor, the impedance at the feedpoint of a small loop antenna is inductive, but an antenna in general certainly aren't "effectively an inductor". It seems to me that the density and composition of the transmission medium you're coupling to has an effect on any antenna's resonant frequency. The conductivity, permittivity, and permeability of the medium in the immediate field of the antenna have a profound effect on the antenna's resonant frequency. Density in and of itself doesn't. This, to my understanding, means that an antenna designed for use in open air will not work underwater, nor will, say, a VLF antenna designed for submarine usage work in open air. It certainly won't work the same as it does in the very different medium. If you believe I'm misunderstanding, then please point me to some documentation on the subject, and I will cheerfully STFU. Any basic antenna text will do. Kraus's _Antennas_ is a good starting point. Roy Lewallen, W7EL |
glass-mount omnidirectional antenna?
On Thu, 12 Jan 2006 19:08:07 -0800, Dr. Anton T. Squeegee
wrote: In article , says... Nothing to do with coupling the Tx energy to the "atmosphere". Terminating the line in a resistor of the line's charactertistic impedance will present a nice SWR and radiate very little. I beg to differ, and I would invite you to think further on this topic. An antenna is a coupling device. Its purpose is to efficiently "couple" or radiate your signal into another transmission medium (open space, including our atmosphere). The antenna (effectively an inductor) needs to be resonant at your operating frequency of choice. It seems to me that the density and composition of the transmission medium you're coupling to has an effect on any antenna's resonant frequency. This, to my understanding, means that an antenna designed for use in open air will not work underwater, nor will, say, a VLF antenna designed for submarine usage work in open air. If you believe I'm misunderstanding, then please point me to some documentation on the subject, and I will cheerfully STFU. Pity you snipped your original statement: "SWR = Standing Wave Ratio. Put simply, it has to do with how good of a load the antenna presents to the transmitter, and how efficiently it will couple the transmitter's energy to the atmosphere." Roy has kindly addressed the antenna aspects. But because you snipped, the essence of my comment was cut adrift. A nice 50R resistor will not "couple the transmitter's energy to the atmosphere" at all efficiently, but should certainly provide a rather good match to your 50 ohm line. You should not attempt to equate radiation efficiency with line matching. I suggest you need to think further, or stick to plumbing. |
glass-mount omnidirectional antenna?
On Thu, 12 Jan 2006 07:28:13 -0500, "xpyttl"
wrote: However, OP has another problem. Nobody has mentioned feedline loss. The wire carrying the signal to the antenna, even with a good SWR, can be a real source of loss, especially at 2.4G. Cable which has a low loss at that frequency is available, but it is expensive and hard to get. an alternative would be using TVSat 75ohm cable & connectors properly lenght cut to mirror Z from source 50ohm to antenna (taking care of cable velocity factor & unpair 1/4 multiple wave lenght proper cut); this way is cheap ... -- Seasons Greetings & Regards , SPAJKY ® mail addr. @ my site @ http://www.spajky.vze.com more than 3y - "Tualatin OC-ed / BX-Slot1 / inaudible setup!" |
glass-mount omnidirectional antenna?
In article ,
says... snippety Just curious. Do you recall how much the windows were tinted? I suspect one of the many reasons for problems is the tinting medium in/on the glass. Actually, yes, they were. And you're right -- Tinting which has metallic content is one of the worst offenders. I can't be certain whether the tint on these specific cars was metal-bearing. I just know that I've always had problems with glass- mount antlers, no matter if the window is tinted. Keep the peace(es). -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. (Known to some as Bruce Lane, ARS KC7GR, kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com "If Salvador Dali had owned a computer, would it have been equipped with surreal ports?" |
glass-mount omnidirectional antenna?
In article ,
says... snippety Roy has kindly addressed the antenna aspects. But because you snipped, the essence of my comment was cut adrift. A nice 50R resistor will not "couple the transmitter's energy to the atmosphere" at all efficiently, but should certainly provide a rather good match to your 50 ohm line. You should not attempt to equate radiation efficiency with line matching. I suggest you need to think further, or stick to plumbing. I thank you for your opinion. I would also remind you that there's no need to be insulting. A simple "I disagree, here's what you might want to look at" will do. Consistently telling someone to "stick to" one thing or another is more likely to get you dropped into a filter file, and subsequently ignored, than it is to get you listened to. -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. (Known to some as Bruce Lane, ARS KC7GR, kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com "If Salvador Dali had owned a computer, would it have been equipped with surreal ports?" |
glass-mount omnidirectional antenna?
On Fri, 13 Jan 2006 22:21:12 -0800, Dr. Anton T. Squeegee
wrote: In article , says... snippety Just curious. Do you recall how much the windows were tinted? I suspect one of the many reasons for problems is the tinting medium in/on the glass. Actually, yes, they were. And you're right -- Tinting which has metallic content is one of the worst offenders. I used an on the glass mount on the rear window of my TA . Part of the tinting has a metallic content, but was in the form of little circles or dots. The rest of the window had a dark tint. The antenna worked fine. Prior to that I used one on a Thunderbird with no problems although it did get out better on the TA. I can't be certain whether the tint on these specific cars was metal-bearing. I just know that I've always had problems with glass- mount antlers, no matter if the window is tinted. They have always worked well for me and generally you can tell by looking at a tint whether it is metallic or not. They "look metallic" with a silver tint. I've not seen any of the tan, green, or brown tints that were metallic. I ran a TM-D700 and a TM-V7A running 50 watts on 144 to these with no problems. They didn't seem to mind the higher SWR on 440 and did well there too. I currently use a diamond mag mount with a colinear on top of a SUV and that is a real performer. 73 Roger (K8RI) Keep the peace(es). Roger |
glass-mount omnidirectional antenna?
Hi Kevin:
the main reason you didn't find one is the glass losses! at 2.4GHz, the loss of most kinds of glass winshields are made of, is so hi as to defeat operation! using a different base, such a cellular one will work, since it has a high pass filtering characteristic, but like I said, the glass itself can prove to be an insurmountable hurdle. Saandy 4Z5KS |
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