Microwave Path Profile Calculator

Calculator Inputs

Path Distance (km)

Frequency (GHz)

TX Site Elevation (m)

RX Site Elevation (m)

TX Antenna Height AGL (m)

RX Antenna Height AGL (m)

Effective Earth K Factor

Required Fresnel Clearance (%)

Clutter Allowance (m)

Terrain Profile (distance,elevation per line)

Enter comma-separated values. Example: 6,245 means 6 km from TX and 245 m elevation.

Example Data Table

Parameter	Example Value	Notes
Path Distance	18 km	Total hop length between both microwave sites.
Frequency	6 GHz	Used for Fresnel radius and free-space loss.
TX / RX Site Elevation	225 m / 214 m	Ground elevations above the chosen vertical datum.
TX / RX Antenna Height	32 m / 28 m	Heights above local ground at each site.
K Factor	1.333	Common effective Earth radius assumption.
Required Fresnel Clearance	60%	Typical design target for many links.
Clutter Allowance	0 m	Add tree or structure margin where needed.
Terrain Profile	10 points	Distances must increase from TX to RX.

Formula Used

This calculator evaluates line-of-sight, Earth curvature, and Fresnel clearance for every terrain point along the hop.

1) Antenna Tip Heights

TX Tip Height = TX Site Elevation + TX Antenna Height RX Tip Height = RX Site Elevation + RX Antenna Height

2) Line-of-Sight Height at Any Terrain Point

LOS Height = TX Tip + ((RX Tip - TX Tip) × (d1 / D))

Where d1 is distance from TX to the point and D is total path distance.

3) Earth Bulge with Effective Radius

Earth Bulge (m) = (d1 × d2) / (12.75 × K)

Here d1 and d2 are in kilometers, and K is the effective Earth radius factor.

4) First Fresnel Zone Radius

F1 (m) = 17.32 × √((d1 × d2) / (f × D))

Distances are in kilometers and f is frequency in GHz.

5) Adjusted Obstruction Height

Adjusted Obstruction = Terrain Elevation + Earth Bulge + Clutter Allowance

6) Actual Clearance and Margin

Actual Clearance = LOS Height - Adjusted Obstruction Required Clearance = F1 × (Required Fresnel % / 100) Margin = Actual Clearance - Required Clearance

7) Free Space Path Loss

FSPL (dB) = 92.45 + 20 log10(D) + 20 log10(f)

How to Use This Calculator

Enter the total microwave hop distance and operating frequency.
Provide both site elevations and antenna heights above local ground.
Set the effective Earth K factor for your design condition.
Choose the Fresnel clearance percentage required by your design rule.
Add a clutter allowance if trees, rooftops, or growth margins matter.
Paste terrain points as distance,elevation lines from TX to RX.
Click Calculate Path Profile to view results above the form.
Review the worst clearance point, pass or fail status, suggested extra height, and detailed point table before making design decisions.

Frequently Asked Questions

1) What does this calculator measure?

It checks terrain clearance, Earth bulge impact, Fresnel zone clearance, line-of-sight height, and path loss for a microwave hop using submitted terrain points.

2) Why is Fresnel clearance important?

A clear visual line is not enough. Objects inside the first Fresnel zone can still weaken the signal, raise fading risk, and reduce link reliability.

3) What K factor should I use?

A value near 1.333 is a common planning assumption. Local climate, refractivity, and reliability targets may justify testing several K values during design.

4) Are site elevations and antenna heights different?

Yes. Site elevation is the ground level above a reference datum. Antenna height is the mast or tower height above that local ground.

5) Does this replace a field survey?

No. It supports planning and screening. Final deployment should still verify coordinates, tower details, clutter, seasonal growth, and actual installation constraints.

6) Why can a link fail despite clear line-of-sight?

A path may still fail because of poor Fresnel clearance, multipath fading, weak fade margin, rain loss, frequency congestion, or inaccurate terrain data.

7) Should I enter clutter allowance?

Yes, when trees, buildings, cranes, or future growth might intrude into the path. This creates a more conservative and realistic clearance check.

8) How can I improve a blocked path?

Raise one or both antennas, shift sites, shorten the hop, change routing, reduce obstructions, or redesign around a more favorable frequency and terrain profile.