Thread: a new way of GPS

Originally Posted by brownpage

I looked through the posts in this forum but didn't find anything about a GPS board. So I googled and find some results. I think some of you guys may be interested.

I am working on my carpc and I want to make the GPS builtin instead of external. I am putting my car-pc in a single DIN, so I hope to put the GPS unit into the DIN too. Hopefully, I found some GPS boards with serial port, so i think i can connect it to my car-pc using a modem wire. And it has an antenna connector, capable of using both passive and active antenna. I am thinking about using the antenna of my car, but I am not sure if that works. I didn't do much research into antenna yet, but maybe that is possible.

And another great thing is that this board is really cheap, I find one guy on ebay who is selling superstar board at $49.00, but I find it a little doubtful, as the connector type is different from what I find from other places.I am bidding on it right now, and I may post about it when I get it.

The link is right here:
NovTel superstar GPS board:
http://www.novatel.com/Products/superstar.asp

and there are several other kinds such as: Jupiter GPS OEM, GPS955, G 12 GPS board from Ashtech. etc... You guys can google on these. I haven't looked much into those.

You would be much better just getting a all in one USB unit. You can't use your car antenna for the GPS, and most all-in-one units are the size of an antenna any way. So they are actually smaller than a board+antenna. And they are the same price if not cheaper when you get the price of the board combined with the antenna.

Originally Posted by Naamanf

You would be much better just getting a all in one USB unit. You can't use your car antenna for the GPS, and most all-in-one units are the size of an antenna any way. So they are actually smaller than a board+antenna. And they are the same price if not cheaper when you get the price of the board combined with the antenna.

So, what's the difference between a car antenna and a GPS antenna? I am no electric technician so sorry for the ignorance. I thought that they both receive signals, only frequency differs. And GPS frequecny is 1575.42 MHz, while FM radio has a frequency of ~ several hundred MHz. So GPS frequecny is not too much different from a radio frequency. So maybe their antenna design is simiar?

But, maybe GPS antenna is not only an antenna, but also includes filter or something else. In that case, it can't be replaced by normal car antenna.

Thanks for advices.

Originally Posted by brownpage

So, what's the difference between a car antenna and a GPS antenna? I am no electric technician so sorry for the ignorance. I thought that they both receive signals, only frequency differs. And GPS frequecny is 1575.42 MHz, while FM radio has a frequency of ~ several hundred MHz. So GPS frequecny is not too much different from a radio frequency. So maybe their antenna design is simiar?

But, maybe GPS antenna is not only an antenna, but also includes filter or something else. In that case, it can't be replaced by normal car antenna.

Thanks for advices.

FM radio is in the 90-110 mhz range. The size of the radio waves is very different. And in simple terms the size of the wave (due to it's frequency) will determine the size of the antenna. The lower the frequency the larger the antenna.

Originally Posted by Naamanf

FM radio is in the 90-110 mhz range. The size of the radio waves is very different. And in simple terms the size of the wave (due to it's frequency) will determine the size of the antenna. The lower the frequency the larger the antenna.

Thanks a lot for the explanation. Yes, FM radio is 90-110mhz range. And that means FM wave has a wavelength of about 3 meters. And for normal AM radio, the range is 535khz-1.7Mhz, that means AM wave has a wavelength of about 300 meters. So we need to pull out car antenna to get better reception of AM signal, which is often not so good.
Then, for GPS, which has a frequency of 1575.42Mhz, that means a wavelength of about 0.2 meters. This is not a so small length compared with the size of car antenna. As we can pull out the antenna to get better reception of AM radio, we may also retract the antenna to get better GPS signal. And, actually I often let my antenna stay very short and the Fm reception is still fine.

no intention to bother. THanks a lot for reply. That makes me more practical on the antenna issue.

Yu will not receive anything with a gps connected to your radio atenna - its more different than you think - You absolutely need a GPS antenna for a gps card - So if you don't want do be dissapointed get you a normal standart USB GPS . Its very small - or get you if youa bsolutely want your module a combo antenna for FM/AM / GPS - these have 2 antennas integrated one for radio one for GPS.

Shortwave is diffenret from microwave ! Shortwave signals are stronger than GPS signals which explains that you can receive them +/- properly -

Get a usb gps

regards

felix

Originally Posted by felix99

Yu will not receive anything with a gps connected to your radio atenna - its more different than you think - You absolutely need a GPS antenna for a gps card - So if you don't want do be dissapointed get you a normal standart USB GPS . Its very small - or get you if youa bsolutely want your module a combo antenna for FM/AM / GPS - these have 2 antennas integrated one for radio one for GPS.

Shortwave is diffenret from microwave ! Shortwave signals are stronger than GPS signals which explains that you can receive them +/- properly -

Get a usb gps

regards

felix

I see. Thanks a lot, man.
I will get a usb GPS then.

The other factor for the antenna is polarization.

A surface radio antenna has vertical polarization (the transmitting antenna is straight up and down...so the waves go up and down).

Most satellite based transmissions use circular polarization.

Your car antenna uses Vertical Polarization.

So yes, you can shorten your AM antenna to match the wavelength, or 1/2 or 1/4 wavelength of the GPS signal; but your polarization is wrong.

If you took a circuit board and etched out a circular antenna that had the correct wavelength, that would probably work.

What if your car had a gps antenna fitted, but no gps unit? Could you use the antenna from that?