## Basic Equations

The LO2 frequency used to track a spectral line at a given frequency Frest centered in the IF band (350 ) is
(6)
and, from eq. (5), the image rest frequency at the band center is
(7)
A little algebra follows

cm and result in

(8)
This result is not independent of the Doppler effect. Accordingly, it the doppler tracking is not exact for the image frequency. and for 2 different values, and , corresponding to different velocities and , we obtain (assuming no change of )
(9)
or, assuming and , and with , , the frequency shift in MHz is
(10)
or, in velocity (in km.s)
(11)