Hi All,
Sparkfun sell http://www.sparkfun.com/commerce/produc … ts_id=8724 this antenna, with connectors for GPS, GSM and WiFi. Has anyone used this product and could tell me if it is possible to use it for GPS and GSM at the same time? Well, not even exactly the same time, but I want to take a reading from the GPS and then send it via GSM. Is this possible, or can I use this antenna for only one of the 3 supported protocols?
If it is directly connected to two inputs the impedance will be messed up. It might be OK if you use something called a duplexer to split the signal whilst maintaining the impedance levels, but it will be a difficult thing to design, and you might lose too much of the signal.
Leon
Just from looking at the unit and data from comparible units, I would say this has separate WiFi, GPS and wireless antennas in one case. So performance would be similar to putting a wireless, GPS, and WiFi antenna next to each other. And you should be able to use all three at once.
Thanks, that was a lot of help. Although it is actually cheaper to buy the separate gprs and gps antennas, im not too happy with the accuracy of the cheapo gps antenna SF sells so I thought id give this one a try. If it can do GRPS as well, then I can kill 2 birds with one stone.
The GPS antenna has virtually zero impact on the accuracy of the GPS fix.
Then please enlighten me as to what does, and why people bother making super sensitive antennas if they make zero difference?
Using the cheap antenna I get around 15-20 metre accuracy. If I use a £50 antenna I have then its accurate to within a few centimetres. At the same time, putting the decent antenna in the glove box in my car reduces the accuracy to about 5 metres, and the cheapo antenna in the glove box just always reads 0 lat 0 lon.
There are a lot of factors which affect the accuracy. The strength of the signal is a major one, and it is the job of the antenna to pick this signal up, so it should make a difference. Granted, if the device itself doesnt take into account multipath or other such problems then the antenna wont make a difference, however as I just stated, the ability of the antenna to pick up the signal is going to have a large impact on the accuracy. Under tree cover, cheap antennas will be useless, under heavy cloud the same issue occurs. Even my sat nav has trouble during the rain, but my decent antenna has no such problems.
And since any statement is useless without evidence to back it up, here are two such articles which agree with me: http://www.cosis.net/abstracts/COSPAR20 … 0394-1.pdf and http://edu-observatory.org/gps/gps_accuracy.html
Fragments of interest from each:
“UEE (User Equipment Errors) includes receiver noise, multipath, antenna orientation, EMI/RFI. Receiver and antenna design can greatly reduce UEE error sources–usually at substantial cost.”
"The preliminary results show that there are big effects of the
antenna offsets on the GPS onboard receiver antenna estimation".
I know that the GPS antenna makes a huge difference to the received signal strength and SNR. I did however forget that the more sats the receiver sees the better accuracy you will have. Sorry :oops: