Moxon Antenna Dimension Calculator
Enter your target frequency and this tool will generate practical starting dimensions for a two-element Moxon rectangle antenna. Values are intended for initial construction, then final tuning with an analyzer.
Tip: for insulated wire, use a slightly lower velocity factor (for example, 0.95 to 0.98).
What this Moxon antenna calculator does
A Moxon rectangle is a compact, directional antenna used by amateur radio operators across HF and VHF bands. It is popular because it delivers useful forward gain and front-to-back rejection while taking less space than many full-size Yagi designs. This calculator helps you quickly estimate key cutting and layout dimensions from a chosen operating frequency.
Instead of forcing you to manually work through wavelength equations each time, the calculator estimates geometry for the driven element and reflector using practical ratios that builders commonly use for first-pass designs. After building, you can trim and tweak dimensions for best SWR, feed impedance, and pattern at your specific installation height.
Moxon geometry basics
A Moxon is essentially a two-element beam (driven element + reflector), where the wire ends are folded inward. This folded shape improves coupling, helps compact the footprint, and often produces a better front-to-back ratio than a simple two-element beam with straight elements.
Key dimensions you will see in the results
- Driven horizontal section: each long straight section of the driven element.
- Reflector horizontal section: each long straight section of the reflector element.
- Folded end leg: each bent side leg at the ends of both elements.
- Element spacing: separation between driven and reflector elements.
- Feed gap: opening at the center of the driven element for your feedline connection.
- Tip gap: spacing between inward-facing folded tips.
- Total wire lengths: approximate cut lengths for driven and reflector wires.
How to use the calculator effectively
1) Choose your center frequency
Pick the frequency where you want best performance. For example, if your SSB activity is around 14.200 MHz, use 14.2 MHz. If you mainly operate CW lower in the band, select that frequency instead.
2) Enter realistic element diameter
Wire thickness and tubing diameter affect resonance and impedance. Thicker elements generally broaden bandwidth and slightly shift resonant behavior. This tool applies a simple correction factor so your first cut is closer.
3) Set velocity factor
Velocity factor compensates for electrical length differences due to conductor and insulation effects. Bare wire often runs close to 0.98–1.00. Insulated wire may need lower values, frequently around 0.95–0.98 depending on jacket type.
4) Build, then tune
Every installation is different: mast interaction, nearby objects, ground effects, and feedline routing all matter. Use these values as a smart starting point, then fine-tune in small steps while checking SWR and resonance with an analyzer.
Construction notes for better on-air results
- Use non-conductive spreaders (fiberglass or similar) for stable geometry.
- Keep bends crisp and symmetrical; asymmetry can degrade pattern and matching.
- Start with element lengths slightly long; trim gradually.
- Add a current choke (1:1 balun) at the feed point to reduce common-mode current.
- Mount high and clear of metal objects whenever possible.
Practical tuning workflow
Initial checks
After assembly, verify continuity and feedpoint wiring first. Sweep the intended band and note the SWR minimum frequency. If resonance is below target, shorten elements slightly. If resonance is above target, lengthen if possible.
Fine adjustments
For small shifts, adjust in tiny increments and keep a build log. Tune one variable at a time: length first, then spacing/gaps if needed. This avoids chasing multiple interactions at once.
Frequently asked questions
Is this calculator accurate enough for final dimensions?
It is designed for reliable first-pass dimensions. Final performance should always be confirmed with measurement tools and practical adjustments at the real installation site.
Can I use it for 20m, 17m, 15m, 10m, or 2m?
Yes. Enter the desired frequency in MHz and build to scale. Mechanical construction details become more critical at higher frequencies because dimensions are smaller and tolerances tighter.
Does wire vs tubing matter?
Yes. Diameter affects current distribution, bandwidth, and tuning. If switching from wire to aluminum tubing, recalculate and expect to re-tune.
Safety reminder
Keep antennas and masts far from power lines. Follow safe climbing and rigging practices, and check local regulations. RF systems can cause injury if improperly installed or operated. Always prioritize electrical and structural safety.