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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 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.

Reply to
kevincw01
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Doz hath wroth:

Nope. The losses can be made to be rather small. With resonant cavity coupling, my guess is 3dB at most. Are you looking for something that will mount on the glass, or something that will got THROUGH the glass with the antenna outside?

However, there are bigger problems with some glass mounts.

  1. Most auto windshield glass has an aluminized anti-reflection tinted coating to prevent overheating the car in the hot sun. This blocks any coupling. Sirius and XM have the same problem. In the last 7 or so years, the tinting is in the glass, not on the surface and is metalized.
  2. Permanent mount glue used by some glass mount antennas tends to be, ummm.... permanent. Removal always destroys any coating (i.e. mylar film, tinting, etc). Attachment directly to the glass works, but if there's a film, the antenna usually falls off, peeling the coatin, on impact.
  3. The mobile wi-fi internet market is not suffiently large to justify such a product. It may be in the future.
  4. A panel antenna, hung in the window, is probably more effective and cheaper to build. However, it is not omni-directional.
  5. The 5dBi gain that can easily be achieved with a reasonable omni antenna, will be lost in the combination of the coupling loss and losses in the tiny coax normally used (RG-316a/u). Any more gain will result in an extrememly narrow vertical beamwidth, which will make a vehicular omni difficult to maintain a connection. Incidentally, the XM antenna has a beamwidth of about 90 degrees, in order to cover the entire sky. A 5dBi omni has a vertical beamwidth of about 30 degrees. These are quite different animals.

It's possible to build a thru-glass omni 2.4GHz antenna, but I'm not all that thrilled with the complications.

Reply to
Jeff Liebermann

The losses would be pretty large...

Reply to
Doz

I don't think "most" is the right adjective here. This metalization affects GPS receivers and FasTrak trasnponders.

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a few.

I am surprised that there aren't better lists. What I find is "check the signal inside and outside the car to see if you have ... "

Reply to
dold

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