Profiles Antenna

Profile: antenna

Antenna modelling, transmission lines and coverage prediction

Stage: 1.0

Who it is for

An operator who builds antennas and wants to model one before cutting wire, measure it afterwards, and predict its coverage.

At a glance

Stage	1.0
Units	12
Disk	about 150 MB, plus terrain when map regions are set
Hardware	None to model. A NanoVNA or other analyser to measure; those need serial access (the dialout group).
Consent	none
Install	hammunition install antenna

What it installs

NEC2 in two forms — interactive with a live pattern display, and as a scriptable engine — plus three specialised modellers for the geometries NEC handles awkwardly: Yagi arrays, Moxon rectangles and Cassegrain dishes. Then the things that connect an antenna to reality: an arbitrary transmission-line solver, terrain-aware path analysis and coverage maps (SPLAT! and Signal-Server, with their terrain made from your map regions' elevation), a locator distance and bearing tool, and desktop front ends for the two analysers people actually measure with.

Disk footprint: Around 150 MB of software, plus the terrain when map regions are set: about 39 MB of Copernicus elevation and 7 MB of SPLAT files for each one degree square the regions touch (measured on one tile), and the regions' map extracts, which dem-copernicus brings with it. A US state is tens of squares.

Why these belong together

Antenna work is a loop — model it, build it, measure it, find out the model was optimistic, change something. Splitting the modellers from the analysers would break that loop across two installs. wwl, splat and signal-server are here because a beam heading, a path profile and a coverage map are questions you ask about an antenna, not about propagation in general.

Packages (12)

xnec2c, nec2c, yagiuda, fl-moxgen, cassbeam, atlc, splat, splat-sdf, signal-server, wwl, nanovna-saver, flaa

What it deliberately excludes

General propagation prediction, which is propagation — VOACAP answers "will this band be open", and this profile answers "what does my antenna do". They are different questions and both are optional. Rotator control lives in station with the rest of hamlib. LibreVNA-GUI is in electronics rather than here: it is a 14-minute source build of a bench instrument's program, and an antenna analyser is not the only thing it measures.

Install it

Read the plan first. It changes nothing and prints every package, build, file and system change, and every consent gate you will meet:

hammunition show antenna
hammunition install antenna --dry-run

Then do it. The engine asks for your sudo password once, near the start, and shows the same plan again before it asks you to confirm:

hammunition install antenna

A member your machine cannot take is deferred by name and the rest installs (D-039); the plan lists each under Will NOT happen, with the reason and the command that fixes it. Installation explains how to read every part of the plan.

What you configure by hand afterward

SPLAT! and Signal-Server need terrain data and will run without it, assuming a flat earth at sea level and producing plausible output that is worthless. splat-sdf makes that terrain from the elevation of your map regions, so set them first (hammunition station set --map-regions ...); with none set it is deferred by name and the rest of the profile installs. Then run hammunition maps splat once as yourself, which points SPLAT! at the files through ~/.splat_path and prints Signal-Server's -sdf argument. With regions set, this profile also downloads their elevation tiles and their map extracts, both listed with their sizes in the plan. NanoVNA-Saver and flaa need access to their instrument's serial port, which means the dialout group and a session started after you were added to it. NEC2 has real modelling rules about segment length and wire diameter, and breaking them produces confident, wrong answers rather than errors.

Your first ten minutes

1. If you want coverage maps, choose your map regions first (hammunition station set --map-regions <region>, see Offline navigation for the region paths); with none set, the terrain units are deferred by name and the modellers still install.
2. Read the plan: hammunition install antenna --dry-run. With regions set it lists elevation tiles and map extracts with their sizes; read those numbers before you agree.
3. Install: hammunition install antenna.
4. Point SPLAT! at its terrain once, as yourself and not with sudo: hammunition maps splat.
5. Open xnec2c and load one of its bundled example models to see a live radiation pattern before you try your own. NEC2 gives confident wrong answers when segment length or wire diameter breaks its rules.
6. If you have a NanoVNA, join dialout with hammunition hardware apply, log out and back in, then open nanovna-saver.
7. A coverage plot from your own grid centre is worked through in Propagation and solar conditions.

Take it off again

hammunition uninstall antenna --dry-run
hammunition uninstall antenna

This removes what Hammunition itself installed and nothing else. It does not remove dependencies apt pulled in, group memberships or configuration files it wrote; the plan says so and the transaction log records them (D-004).