I couldn't get "jTether" (JB WiFi Tether) to work at all; I got a generic system error message saying "Unfortunately, jTether has stopped" whenever I tried to launch it.
However, I WAS able to get tethering working using a different route:
1) Instead of jTether, install "
Portable Wi-Fi hotspot" from the Play Store (
link). When you run it the first time, it brings up the Android tethering settings, which Optimus F3 users don't normally have access to. After the first time, it simply toggles tethering on or off; you can't get back to the config screen unless you clear this app's data.
2) Install the "
Wireless Tether for Root Users" APK from code.google.com (
link). For me, v2.0.7 works but the v3 beta doesn't. Run it after you have tethering turned on by the first app.
Obviously, root is required, for both steps.
NOTE: Every time I start up tethering in the "Wireless Tether" app, it says "Tethering started with errors!", and the "Show log" command fails, but tethering DOES work nonetheless. I think the errors are coming up because it wants to set the name of the hotspot and other details, but those have already been handled by Step #1. (The HTML-based log file does exist, at
/data/data/android.tether/var/tether.log, but the "show" function in the app doesn't know where to look for it!)