Skip to content

voacapl

The VOACAP HF propagation prediction engine, ported to Linux

What it does

Predicts HF circuit performance between two points: which bands will be open at which hours, the probability of a usable signal, the expected signal-to-noise ratio, and the required power for a given reliability. It is the Voice of America Coverage Analysis Program -- the model broadcasters used to plan shortwave schedules -- with its Fortran core intact.

Why you would want it

Predictions from a real ionospheric model are a different thing from a band condition indicator. Given a date, a smoothed sunspot number, two locations, antennas and power, it will tell you which hour to try and which band, which is the difference between calling CQ into a dead band and working the path. It also underlies pythonprop and several online predictors, so learning it once pays off elsewhere.

Before it will work

A smoothed sunspot number for the month in question, which is a prediction itself and which you supply. The coefficient data is in the voacapl-data package, which this one depends on. Antenna files describing what you actually have, if you want the answer to be about your station rather than about a dipole.

How it installs

  • apt: voacapl

Known problems

It is a Fortran program with a command-line and file-based interface designed in the 1980s, and the input file format is unforgiving. Most people should drive it through pythonprop rather than directly. The model predicts monthly medians, not tonight: a prediction that says a band is open 60 percent of the time is not wrong when the band is shut, which is the most common misreading of its output.

Keeping it current

  • probe: apt policy
  • strategy: apt_upgrade

Where to get help with the software itself

Jim Watson, HZ1JW / M0DNS, maintains the Linux port. The project page carries the documentation, which is worth reading before the first run.

Source: catalog/packages/voacapl.yaml