When the VCO is modulated by a triangular function +/- 6V, a small fluctuation is observed in transmitted and reflected beam. There might be some small constant phase shift between the two.

at 78 MHz  the modulation width is about 0.3 MHz, with +/- 2.4% amplitude

 at   79.5 MHz,  the width is 0.238 MHz, +/- 1.1 % in amplitude,

  at 81 MHz, the width is 0.193 MHz, +/- 1.5% in amplitude.

The first plot shows the comparison between the transmitted beam and the reflected beam between 78 - 82 MHz. The second and the third plots are the whole data from the transmitted beam and the reflected beam respectilvely. The data is taken aroud 2010-02-03 20:00:00 UTC.