Radio Mobile for Windows

by Ric - [email protected]

At the April club meeting, Ric Tell, K5UJU, gave a brief presentation on RF propagation modeling with application to the Colville repeater. Ric generated this figure as one illustration of how the powerful software package from VE2DBE "Radio Propagation and Virtual Mapping Freeware" can be applied. This figure shows projected field strengths at 2 meters above ground from the Colville repeater in this region. [Click on the figure for a larger view.] The software package provides for the downloading of digital elevation data from the Internet for regions that the user defines and applies a propagation model to calculate the estimated field strength throughout this region. In this figure, the terrain elevation data have a spatial resolution of 1 arc second which is approximately equivalent to 30 meters or about 100 feet. This means that the Earth elevation is obtained over a grid with a spacing of about 100 feet between elevation points. When downloading the digital elevation data, this can amount to fairly sizeable files, depending on the extent of the region being modeled. In this figure, the field strength is keyed to various colors via the legend in the far upper left hand corner of the figure. The electric field strength in decibels relative to a microvolt per meter is used to color the terrain map.

For this illustration, details about the Colville repeater were obtained from the repeater trustee Randy, N7CKJ, including transmitter output power, transmission line type and length, antenna type and gain, antenna mounting height, and directional characteristics of the antenna installation (the antenna is mounted on the eastern facing side of the tower resulting in a presumably slightly enhanced radiation to the east).

The software allows for the inclusion of any number of network units within the region and it can be used to calculate the signal strength between the repeater and each unit or signal strength between any two units. It also allows for a determination of the visual line of sight from any given point to the whole region in the vicinity.

Composite RF field strengths produced by more than one fixed station can also be calculated. Ric plans to run another analysis showing coverage for both the Colville repeater as well as the Lookout Point repeater near Spokane that is linked with the Colville repeater once he gets all of the necessary technical information about the Spokane facility.

Anyone interested in trying the propagation modeling software can download it free on the Internet at http://www.cplus.org/rmw/ (rmw stands for Radio Mobile for Windows). Ric can be reached at [email protected].