Thanks for posting in the Slingbox Answers Forum! I'm sorry to hear you are having trouble connecting to your Slingbox when your android phone is using a 3G network connection.
This is because the Slingbox does require a bit of bandwidth to be able to connect to it. 3G/4G connections often drop. However, you can install a speedtest application to your phone, and test the speed you are getting from the 3G/4G network.
The requirements for SlingPlayer for android phones are 250kbps on the phone and also on the network at the location of the Slingbox. I have provided an article below for SlingPlayer for Mobile Devices. If you go to SlingPlayer for Android Phones and click on Requirements for SlingPlayer for Android Phones, it will also show you this information.
Here is the link:
Hope this helps!
The Sling Moderation Team