I recently purchased and installed a Hirschmann GPS 2400 antenna (GSM, GPS, 802.11) and, like others, wanted to attempt to use my existing USB GPS receiver (Holux GM-210) with it. I had thought of getting a re-radiating antenna, but wasn's sold on the idea yet. I had read of others trying to solder a pigtail in place of the internal antenna with no success. I figured excessive heat had destroyed sensitive parts and I really wanted to solder an SMA connerctor in place of the original antenna, so that i could connect it to my GPS 2400. What follows is a step-by-step descrioption of taking apart the Holux GM-210. (spoiler.... no it didn't work, but I was able to restore functionality by reversing what I did, I think this is still useful information)
1. The case is not screwed together. There is nothing under the magnets. To open it up, I just inserted a small flathead screwdriver in the groove on the side and pryed it open. There are 4 little plastic clips and sealing glue that hold it together, 2 of the clips ended up breaking for me. It also won't be waterproof after this (unless you glue it again) (sorry for this blurry image, just to show there's nothing under the magnet)
2. Once opened you see the antenna.It is adhesed to the metal ground plane, and the easiest way to get it off is by desoldering where the metal shield is soldered to the board. BE CAREFUL, too much heat will damage IC's. I used a 15W iron.
3. Once the ground shield is off, you can see the wire for the antenna. Desolder the center wire, and then gently pry off the antenna.
Again, sorry for the blurry image below
4. Then Desolder the antenna wire.
5. I drilled holes for the SMA connector
6. And soldered the SMA connector in place. This thing is VERY secure.
7. Solder on the antenna wire.
8. Solder the ground shield back onto the board. (Test if you want)
9. Then I drilled a (horribly ugly) hole in the top of the GM-210 case
10. Then I reassembled the whole thing and put on my SMA-FME adapter
To my dismay I could not get a lock on the satellites. The LED stayed green, and never started to blink. I downloaded GPS viewer and SIRFdemo to try to diagnose the problem, but couldn't get a reading. The device still showed up as "Holux USB GPS device" (or something like that) in my device manager, so I was still hopefull. I then tried to solder the original antenna (with improvised ground plane) to the end of a FME-pigtail. Also didn't work at first. Then it started to sporadically read satellites in GPS viewer. I tried connecting it to the GPS 2400 antenna, and nothing. Then I got frustrated and decided the Holux probably doesn't like the GPS 2400 antenna, probably not designed to power an external antenna (dunno if that makes sense). So undid everything I had just done, removed the SMA connector and resoldered the original antenna in its factory position. Then I went to test it, and it was glitchy at first, but after about 10 minutes of switching between softwares, it started to get a lock.
The only difference now is that when being used in DeLorme Street Atlas I now occasionally get a 3-D DGPS lock where as before it would only get 2-D or 3-D locks (still get both of those). A quick reading of the help file shows that "a WAAS enabled device will give a 3-D DGPS lock". I'm not sure if it is good that I now get this when before I didn't, but I don't really care.
Hope this helps someone who wants to open up their Holux GM-210