Empirical Study of Water Impact on Forward Signal i Feed Line for VHF Communication

Abstract

The properties of radio wave propagation in feed line are studied, and the power level is examined to determine the effect of water in coaxial feed line during radio wave propagation. A 50-ohm, 3 1/8 inch coaxial feed line was connected between the BE20S solid-state transmitter of 0.5 kW step and antenna at 100m above the earth. Two cases were considered; the case of a matched feed line without water and a case of matched feed line with 25c1 of water in it. A spectrum analyzer was deployed to monitor the behavior of the wave propagation pattern during these two cases of transmission. Transmitter’s display board was used to monitor the forward and reflected power level. An increase in the forward power lead to gradual increase of reflected power during case I, compared to rapid increase in the reflected power during case II. This confirms the effect of water in feed line during radio wave propagation for VHF communication, as it rejects more of the forward power to the transmitter, which can lead to destruction of the transmitter if not shut off due to this effect.