The SD-502 SDIO GPS Review
It is difficult to review the Globalsat SD-502 without referring to it's predecessor the SD-501, but they are completely different. For starters the GPS chipset is the latest SiRFStarIII, then the antenna is a double helix, then of course the whole thing has a healthy 512Mb of memory.
Starting at the beginning the GPS has a new smart silver casing. There is a cover provided for the lower connector section of the GPS which protects the connectors from damage during storage. You will notice the absence of pictures of this cover here. I managed to loose mine!
At the top of the GPS is a black round tube. This houses the double helix antenna. All of this is implemented in a nice compact format that doesn't waste any space at all and is quite minimalistic.
The size of the exposed main body of the receiver is about the size of an SD card, plus half as much again for the antenna.
As the power for the SD-502 is taken from the host PDA there is no need for an on-board battery. This makes the GPS Receiver extremely light. With the power requirement of 90Ma there is only a small drain on the battery.
The SD-502 also sports a "double helix" antenna. What? I hear you ask. Well most GPS receivers use what is known as a patch antenna. From what I am told a patch antenna is pretty easy to tune and integrate. The double helix antenna on the other hand is much more difficult. You can see this to the right where the white tube is, the bands of copper and the tube form the antenna.
So why use the double helix then? Well the simple reason is that the patch antenna is good, but it only works well in one plane. i.e. the antenna needs to be pointing up at the sky. The double helix is not sensitive to position at all and, although slightly less sensitive than a patch antenna, will work well no matter what the orientation of the GPS is.
This is important for our usage models in PDAs as there is no telling how the PDA will be used. Indeed I will often have mine horizontal whilst walking but vertical in the car. Sometimes I have it vertical, but rotated into landscape mode. The double helix antenna copes with all of these positions well.
As you can see from the images to the right. my GPS came to pieces in my hands again... Well it did need a screwdriver as well, but is was a complete accident (honest!!).
It was almost not worth opening it up. There was little apart from the antenna to see. Most of the rest of the GPS receiver is heavily shielded. This of course is a good thing as it means that the weak and sensitive GPS signals are not affected by interference from other sources.
You can also see that the GPS is created using 3 modules: the connector; the GPS engine and the antenna.
Before you can use the GPS or the memory you need to install the driver on your PDA. I would recommend visiting the Globalsat download page and getting the latest version of the driver. It has been updated since the release of the product to market.
The driver is installed over activesync and once installed the GPS and memory will be visible. To actually see the GPS and memory you may need to perform a soft-boot on your PDA.
The memory is only available on the PDA, or on a PC through activesync. It is not possible to use it directly on your PC with a card reader. This means that transferring map data can take a long time to complete.