How to use HFTA-X, step by step
From an empty map to a decision about your tower height in a few minutes. No formulas: what to press, what you are looking at and what to do with it. If you want to learn HFTA, it is also the quickest way in: the ideas are the same, terrain profiles, elevation pattern and figure of merit.
1. Place the tower
In section 1 · Tower location, click the map where the tower is or will be, or type the latitude and longitude. Be precise: the terrain that matters is the next 4 km or so, and a few hundred metres can change it.
2. Build the terrain profiles
In 2 · Terrain profiles, type the directions you care about. One azimuth (300), a list (30,45,60) or a range with a step (0-355/45). Press Show terrain to see each profile.
In Spain and the United States the profiles come from LiDAR bare-earth models, which ignore trees and buildings. Elsewhere they come from SRTM radar, which sees the treetops, so a forest in front of the tower looks like a hill. The program always says which source it used, and the reliability check warns you when the difference is vegetation rather than relief.
3. Describe the antenna
In 3 · Antenna and frequency, choose a dipole or a Yagi of 2 to 8 elements, the height and the band. Stacks of up to four antennas are available in advanced mode. Then press Compute radiation pattern.
4. Read the elevation pattern
The horizontal axis is the take-off angle; the vertical axis is how much signal leaves at that angle. Peaks are angles your antenna does well; valleys (nulls) are angles where almost nothing leaves. Tick Flat-ground reference to see the same antenna on a plain: the gap between the two curves is what your terrain gives or takes away.
5. Compare with the angles you need
The further away the station you want to work, the lower the angle. Nearby Europe from Spain needs 20° to 50°; North America and Japan need roughly 1° to 20°. Section 4 · Elevation-angle statistics (FOM) loads the statistics for the region, and the bars on the chart show how often signals arrive at each angle. The figure of merit (FOM) sums it up in one number: use it to compare options, not as an absolute measurement.
6. Optimise the height
In 5 · Height optimiser, give the range of heights you can actually build and press Optimise height. You get gain and FOM against height, and the range of heights where the antenna works best. A wide range means a couple of metres either way does not matter; a narrow one means it is worth being precise.
7. Look all the way round
Global performance turns the antenna through every direction, works out the terrain each way and draws the result as a rose with the DX regions on it. You can compare up to three heights at once and see, for example, whether going higher helps towards Japan but hurts towards Europe.
8. Check when each band opens
The Propagation tab computes VOACAP maps by band and hour. Look at Reliability: the share of days in the month on which the contact works at that hour. Set the mode you operate (SSB, CW or FT8), because each needs a different signal level. These are monthly medians, not a forecast for tomorrow.
What it does not do
It does not design antennas or tell you the SWR: it assumes the antenna works and calculates what the terrain does to it. And the absolute numbers are less reliable than the comparisons: it is a tool for choosing between heights, antennas and sites.
HFTA-X is an independent project. It is not affiliated with or endorsed by the ARRL. HFTA (HF Terrain Assessment) is a program by R. Dean Straw, N6BV, published by the ARRL.