  In this paper we describe the development of novel RF exciter circuit for
electrode less Rb lamp. The lamp exciter circuit is a RF oscillator with a a
new configuration operating at 60 to 65 MHz frequency with 3 to 4 watt power.
The Rb lamp is used in exciting the ground state hyperfine transitions in Rb
atom in a glass cell placed inside a tuned microwave cavity, As the frequency
of these hyperfine transitions is very stable it is used in the development of
Rb atomic clock by phase locking the oven controlled crystal oscillator (OCXO)
to this atomic transition frequency. The details of the Rb lamp exciter are
presented in the paper.The Lamp is ideally operated in ring mode as in this
mode the linewidth is narrow and there is no self reversal. However, high
temperature and RF excitation power may drive the Rb lamp to red mode which
gives rise to line broadening and self reversal. It is the experience that mode
change from ring to red deteriorates the atomic signal strength and S/N. In
this paper the reasons of mode change are also discussed.
