[PyQt] show dialog

[Phil]

Thank you for reading this.

I think my previous post went unanswered because it was too cluttered 
with unnecessary code, so I'll reduce it to the minimum.

I'm trying to have a dialog displayed from a menu item on the main window.

The dialog is defined as;

class SatelliteListDialog(QDialog, Ui_Dialog):

And this is the menu function within mainwindow;

def on_actionList_triggered(self):
	self.dialog = SatelliteListDialog()
         self.dialog.show()

This is the error message;

"global name 'SatelliteListDialog' is not defined"

I've played with this hours and not discovered the answer. By the way, 
I've imported the file where SatelliteListDialog is defined. There 
aren't error messages related to that but could there still be a problem 
with the import, a path perhaps?

-- 
Regards,
Phil