To make the tower location selection process more efficient, it is important to begin with RF coverage maps, a tool typically used in mobile communications. By adapting these maps to reflect microwave-specific parameters, it is possible to prescreen large areas, identify potential line-of-sight paths and significantly reduce the number of infeasible candidate sites before initiating detailed point-to-point RF studies.

At the beginning of the design process, these coverage maps identify areas where tower parameters meet project requirements and help visualize signal strength. By adjusting map settings to match the requirements of point-to-point microwave paths, it is possible to quickly identify all locations where there is sufficient signal strength.

Using RF coverage maps at the beginning of the process reduces the time needed to evaluate sites, increases the likelihood of starting with viable locations and minimizes rework. Instead of waiting for a real estate team to propose sites based on elevation, a team can use coverage maps to pinpoint areas that meet the technical RF requirements, rather than just relying on where the site elevation is high or low. 

Unlike cellular systems, which rely on omnidirectional antennas to spread signals across large geographical circular areas to communicate with mobile radios, microwave networks depend on precise, line-of-sight (LOS) links between towers in fixed locations. Obstructions such as buildings, trees, or terrain can disrupt connectivity, making accurate site selection essential.

Traditionally, microwave path design depends on point-to-point RF studies, which involve detailed terrain and obstruction analysis between two fixed points as shown in Figure 1. 

When clients want to build a new tower or move off of existing leased towers to a new unspecified location the traditional approach presents several challenges, primarily due to its time-consuming nature and lack of scalability. Each proposed site must be individually analyzed for terrain profiles, clearance assessments and height calculations. When endpoints change or repeaters need to be introduced, the entire evaluation process must be restarted. (See Figure 2.)

Many locations initially considered for new towers ultimately fail feasibility checks due to obstructions or excessive link distances. This leads to repeated site assessments and the result is an extended cycle of rejected locations and prolonged network planning efforts.

Another significant limitation of traditional RF point-to-point studies is their focus on individual link assessments rather than a broader, regional analysis. As microwave networks expand, the manual evaluation of multiple sites becomes increasingly complex and resource intensive. 

Integrating RF coverage maps into the site selection process allows a highly directional microwave dish to be modeled as an omnidirectional source. This enables a broader coverage view not typically available in traditional point-to-point RF studies, bridging the gap between wide-area feasibility assessments and focused link analyses. It offers a better perspective for making informed decisions.

By configuring coverage maps to account for microwave-specific parameters such as frequency bands, antenna gain, antenna height and microwave radio parameters, it is possible to visually identify areas with a high likelihood of LOS connectivity. This prescreening step narrows down viable areas early in the planning phase, reducing the risk of failed assessments. Figures 3 and 4 illustrate how this method is applied by treating intermediate microwave sites similarly to mobile towers and performing RF studies from both far-end locations. 

To validate using the RF coverage map approach early in the process, Burns & McDonnell compared traditional point-to-point RF studies to the new approach that is assisted by RF coverage maps. The project team selected two far-end tower sites and set out to identify a viable intermediate site that could establish line-of-sight communication with both.

Rough boundaries for potential intermediate sites were created by drawing a 10-mile radius around each of the two far-end towers. This visual estimate helped predict where RF coverage areas were likely to overlap, as shown in Figure 5.

RF coverage maps were then generated for the far-end sites using microwave-specific parameters such as antenna gain, antenna height, transmit power, receiver sensitivity and fade margin thresholds. The resulting coverage maps visually represented areas with acceptable fade margins using a color gradient: blue and green signified good margins, while yellow to dark red indicated poor fade margins, as shown in Figure 6.

Using the overlap zone from the coverage maps, the team examined the terrain and fade margin distribution to pinpoint locations (indicated as pink circles) with non-obstructed signal paths and acceptable fade margin from both far end sites as shown in Figure 7. Coverage maps effectively reflected terrain obstructions such as mountain ranges (indicated as a pink straight line) that cause abrupt signal loss, seen as transitions from blue to red along specific paths.

In our example, a valley running through a mountain range permitted signal continuity, making two locations strong candidates for an intermediate site. The signal path through the valley is more clearly illustrated in the lateral view in Figure 8, while Figure 9 provides a close-up of the two potential intermediate sites identified based on acceptable fade margins.

Once sites were identified, the team conducted two critical regulatory checks. First, a Federal Aviation Administration (FAA) Notice Criteria review was performed that showed the proposed tower locations were not near an airport or within a designated glide slope path. This step was crucial for avoiding airspace violations or future construction restrictions. Second, a Federal Communications Commission (FCC) AM tower proximity check was performed to identify nearby AM radio broadcast towers to avoid signal interference risks. Both checks are essential to eliminate sites that could encounter permitting or operational barriers later in the deployment process.

Following the generation of coverage maps and regulatory checks, the information was forwarded to the real estate team. Using these maps as a guide, the team concentrated on identifying purchasable parcels within the viable coverage zones. This targeted approach streamlined the search process and avoided random site selection.

After identifying suitable parcels, the team proceeded with detailed point-to-point RF studies for each candidate location to validate the assumptions made during the initial coverage mapping phase. Point-to-point analysis confirmed that each selected path had a clear Fresnel zone, acceptable fade margin and acceptable path availability.

While the use of RF coverage maps significantly improves planning and site selection, certain limitations must be addressed in order to have optimal site selection results. A few of these include:

• Coverage map precision. One limitation of coverage maps is that they assign a single value to an entire grid cell based on the calculated value at the cell’s center, even though slight fade margin variations may exist within that cell. As a result, the color resolution may not always accurately reflect subtle transitions in fade margin values.
• Lack of Fresnel zone analysis. Cellular coverage maps typically do not account for Fresnel zone clearance, which is critical for microwave links. Even if a map shows signal presence, it doesn’t mean the path is unobstructed through the entire Fresnel zone.

Despite the challenges posed by these constraints, a few key practices and recommendations can still be effectively implemented, including:

• Conduct point-to-point study. While coverage maps are reliable and a great way to start the selection process, conducting a point-to-point RF study remains essential to validating selection results with higher precision.
• Avoid inaccurate conclusions when analyzing results. Coverage map results are dependent on the input parameters such as frequency, antenna height, antenna gain, transmit power, radio model and configuration. Users must keep these parameters in mind when interpreting the coverage maps to avoid drawing inaccurate conclusions about signal viability.

The process of identifying viable microwave tower locations has traditionally relied on point-to-point RF studies for each prospective site. However, when evaluating a large number of potential sites, this method can be time-consuming and labor-intensive. Each site must be analyzed individually to confirm viability, which can lead to inefficiency during the early planning phase.

Ultimately, the technique of overlaying RF coverage maps to find where there is overlap as a way to reduce feasible tower site count is unique and bridges the gap between high-level feasibility analysis and site-specific engineering, enabling faster, more accurate and cost-effective results.

By adapting RF coverage maps early in the site selection process to reflect microwave-specific parameters, it is possible to screen large areas, identify potential line-of-sight paths and significantly reduce the number of infeasible candidate sites before initiating detailed point-to-point RF studies. This methodology leverages powerful tools like Pathloss to take full advantage of features such as real-world map visualization and automated modeling.

As the demand for scalable wireless infrastructure continues to grow, incorporating RF coverage maps earlier in the network planning process represents an innovative approach that plays a vital role in efficient early-stage planning and optimized network expansion.