In the notes below the new DDS system means that the freq ref
is the Ebay GPS-controlled 10MHz oscillator as reference for the
DDS exciters in the tx-hall, and a GPS-controlled clock and
10MHz ref for the tru-time board and radar controller in the control room. 
The tru-time board gives the start signal to the tx-hall RC.

20081128   13:18 UT EISCAT 1pps _|- is  17 us ahead datum 1pps -|_ 

20090127   Using new DDS system (tx-hall exciters)
20090302   19:00 UT EISCAT 1pps _|- is  56 us ahead datum 1pps -|_  Set clock

20090303   18:06 UT Reverted to old system (control-room exciters)                                       =60 us ahead Symmetricom in control room
20090305   23:00 UT power break
20090306   08:24 UT EISCAT 1pps _|- is 10.8usbehind datum 1pps -|_  set clock

20090423   Using new DDS system (tx-hall exciters)
  
20090808   Reverted to old system (control-room exciters)

20091009   Using new DDS system (tx-hall exciters)

20091029   Reverted to old system (control-room exciters)

20091130   Using new DDS system (tx-hall exciters)




03 May 2011
-----------
A Rubidium frequency standard (SRS) is now the 10MHz frequency
reference for the exciters in the transmitter hall. It is free
running, i.e. not disciplined by GPS.


March 12 2013:
--------------
The SRS Rubidium standard in the tx-hall now has an external
1pps added from an Adafruit GPS receiver. This should improve
long-term frequency stability.