Moved vna docstring to new module
+'''
+.. module:: skrf.vi.vna
+++++++++++++++++++++++++++++++++++++++++++++++++++++
+Vector Network Analyzers (:mod:`skrf.vi.vna`)
+++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+.. warning::
+
+ As of 2017.02 a new architecture for vna drivers is being implemented.
+
+New VNA drivers
+---------------
+
+- VNA drivers will now have a common high level functionality across all vendors implemented in an ABCVNA class.
+- Different vendor drivers will implement their own mid level functionality as needed to implement the ABC class
+- The low level functions are all implemented as SCPI commands which have a new way of being generated and called
+
+Legacy vna module
+------------------------
+The old vna.py module containing drivers for PNA, PNA-X, HP8510, etc. will be available as vna_old.py and can be used as
+follows:
+
+::
+
+ from skrf.vi.vna_old import PNA
+
+Available VNAs
+------------------
+
+.. autosummary::
+ :toctree: generated/
+
+ PNA
+ ZVA40
+ HP8510C
+ HP8720
+'''
+
from .keysight_pna import PNA, PNAX
