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.

On 10 Jan 2006 19:23:41 -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 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.

The losses would be pretty large...

Doz <(E-Mail Removed)> hath wroth:

>On 10 Jan 2006 19:23:41 -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 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.

>The losses would be pretty large...

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.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann <(E-Mail Removed)> wrote:

> 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.

I don't think "most" is the right adjective here.
This metalization affects GPS receivers and FasTrak trasnponders.
http://www.transcore.com/support/000...cle%20List.pdf
lists 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 ... "


--
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Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5