Those traders who are using datacard should consider switching to broadband.
WHY??
In trading day the most important thing is data response time rather then Internet speed itself.
For example, general internet browsing, under 200ms to most parts of the world is usually good (under 100ms if the server is in your own country).
200-400 is adequate, depending on how far away the server is, and how many nodes data has to go thru to get there (eg, other side of the world).
400+ ms is really quite bad, but the internet will still function, it will just seem a bit sluggish.
For most online gaming, aim for ~120ms or less (local servers in your own country are usually the best). LAN gaming should be below 50ms easily.
When I tried a dongle from a friend on my computer the response time was 450 ms. which is not good for intraday trading at all.
So try to stay away from dongle, and use broadband connections if possible in your area.
you can check your response time by initiating PING
WWW.GOOGLE.COM and TTL will be your response time.