  In order to investigate the speed of gravitational signals travelling in air
or through a different medium two experiments were designed. One of the
experiments contains 2 masses rotating at very high speed and in the other
experiment a sapphire bar will vibrate, in both cases they will emit a periodic
tidal gravitational signal and one sapphire device that behaves as a detector,
which are suspended in vacuum and cooled down to 4.2 K will act as a detector.
The vibrational amplitude of the sapphire detector device is measured by an
microwave signal with ultralow phase-noise that uses resonance in the
whispering gallery modes inside the detector device. Sapphire has a quite high
mechanical Q and electrical Q which implies a very narrow detection band thus
reducing the detection sensitivity. A new detector shape for the detector
device is presented in this work, yielding a detection band of about half of
the device vibrational frequency. With the aid of a Finite Element Program the
normal mode frequencies of the detector can be calculated with high precision.
The results show a similar expected sensitivity between the two experimental
setup, but the experiment with the vibration masses is more stable in frequency
then it is chosen for the experimental setup to measure the speed of gravity in
short distances. Then a more precise analysis is made with this experiment
reaching a signal-noise ratio of 10 at a frequency of 5000 Hz.
