The essentials in 30 seconds
- VHF range ∝ √antenna height. Doubling height does not double range — Norton’s formula: range NM ≈ 1.22 × √(h_antenna_m). But an antenna at 17 m vs 1.5 m increases range from 5 NM to 25 NM compared to a semaphore (80 m).
- Masthead = standard for cruising. 1 m whip antenna at 17 m height (15 m mast + 2 m). Optimal range, minimal cable loss if RG213.
- Stern rail = backup or small sailboat. For 7-9 m sailboat without mast (sloop dinghy, etc.), 2 m high antenna on stern rail is enough. Range only 5-8 NM.
- RG213 coaxial cable mandatory. RG58 loses 6 dB over 18 m (¾ of power dissipated). RG213 or Belden 9913 loses 2 dB (⅓). The extra cost is negligible, the impact huge.
- Watertight PL259/N connectors: marine-grade silicone grease + self-amalgamating tape at mast-deck junctions. #1 cause of VHF failures in cruising: wet connectors.
A VHF antenna is what turns your radio into a useful safety tool. An excellent VHF (B&G V60-B, Raymarine Ray73) with a poorly installed antenna = range divided by 4. An entry-level VHF with a well-installed antenna = manufacturer’s nominal range. The difference is not in the radio, it’s in the antenna.
For the VHF itself, see our Fixed vs portable VHF + AIS Class B for sailboats — safety. This article covers only the antenna, cable, and connectors.
VHF physics — why height matters
Marine VHF operates at 156-162 MHz. At this frequency, radio waves travel in straight lines (near-optical). They do not bend around Earth’s curvature or pass through large metal obstacles.
Norton’s range formula (in NM):
range ≈ 1.22 × (√h_transmitter + √h_receiver), heights in meters.
- Sailboat (masthead antenna 17 m) to cargo ship (antenna 35 m): 1.22 × (4.12 + 5.92) = ~ 12 NM.
- Sailboat (masthead antenna 17 m) to semaphore (antenna 80 m): 1.22 × (4.12 + 8.94) = ~ 16 NM.
- Sailboat (stern-rail antenna 2 m) to same semaphore: 1.22 × (1.41 + 8.94) = ~ 12.6 NM... in theory. In practice, wave masking reduces usable range to 5-8 NM.
The issue is not just maximum range but practical range in real conditions: rough seas + intermediate obstructions (bimini top, neighboring mast, solar panels). The higher the antenna, the cleaner the signal leaves the boat’s environment.
Masthead antenna — technical details
The masthead antenna is mounted at the top of the mast, ideally 30-50 cm above the masthead to avoid turbulence from the wind transducer or mainsail.
- Type: 1 m rubber/fiberglass whip, gain 3-6 dBi, omnidirectional.
- Brands: Shakespeare, Glomex, Mantagua. Typical price: 80-180 € ex-VAT.
- Connection: PL259 male at base, RG213 or Belden 9913 coaxial cable inside the mast.
- Watertightness: O-ring at the base + self-amalgamating tape on the connector.
Stern-rail or backstay antenna — use and limits
Secondary antenna mounted on the stern rail, backstay, or emergency mast. Typical uses:
- Backup: in case of masthead antenna failure (lightning, broken mast). Always wire the VHF with a 2-position coaxial switch.
- Sailboats without mast: dinghies, sailboats with tilting masts, high-power RIBs.
- Dinghy / tender: portable antenna connected to a handheld VHF when needed.
As a primary antenna, the stern-rail antenna limits usable range to 5-8 NM — insufficient offshore.
Coaxial cable — RG213, Belden, LMR
The coaxial cable between antenna and VHF carries an HF signal that attenuates with length and dielectric quality.
- RG58: 6 mm diameter, loss 0.3 dB/m at 150 MHz. For 18 m mast: 5.4 dB loss = 71% of power dissipated. To avoid.
- RG213: 10 mm, loss 0.12 dB/m at 150 MHz. For 18 m: 2.2 dB = 39% dissipated. The cruising standard.
- Belden 9913: 10 mm, loss 0.08 dB/m. For 18 m: 1.4 dB = 28% dissipated. Premium.
- LMR-400: 10 mm, loss 0.07 dB/m. For 18 m: 1.3 dB = 26% dissipated. Top-tier racing.
RG213 vs RG58 surcharge = 2-3 €/m. Over 20 m mast, that’s 40-60 € ex-VAT difference — vs ~30% range lost.
Watertight PL259 and N connectors
Two standards:
- PL259 (UHF): standard for marine VHF. Average watertightness, quick connection. Must be protected (self-amalgamating tape + silicone).
- N (Type N): pro/military standard. Native watertightness (O-ring), tighten with a wrench. More expensive, less common in cruising.
Critical junctions:
- Mast base: junction between cable exiting the mast and deck cable exposed to seawater. PL259 + self-amalgamating tape + silicone.
- Masthead: O-ring under the antenna, greased stainless screws.
- VHF rear: connection to the radio’s antenna output. Check tightness annually.
Comparative table of configurations
| Configuration | Antenna height | Cable | Range to semaphore | Ex-VAT budget |
|---|---|---|---|---|
| Masthead + RG213 | 17 m | RG213 (18 m) | 16 NM theoretical, 14 NM practical | ~ 350 € ex-VAT (antenna + cable + connectors) |
| Masthead + Belden 9913 | 17 m | Belden 9913 (18 m) | 16 NM theoretical, 15 NM practical | ~ 450 € ex-VAT |
| Masthead + RG58 | 17 m | RG58 (18 m) | 16 NM theoretical, 10 NM practical (cable losses) | ~ 280 € ex-VAT (not recommended) |
| Stern rail + RG213 | 2 m | RG213 (5 m) | 12.6 NM theoretical, 5-8 NM practical | ~ 250 € ex-VAT |
| Backstay + RG213 | 14 m | RG213 (15 m) | 15.5 NM theoretical, 12 NM practical | ~ 330 € ex-VAT |
5 installation errors observed
Antenna errors — Skysat workshop
- RG58 cable inside the mast. Ridiculous savings, 60-70% range loss. Always use RG213 minimum.
- No self-amalgamating tape at mast base. Water infiltrates the connector, causes shorts. Intermittent failures are hard to diagnose.
- Antenna not straight (permanent rigging heel). If the mast is not vertical at rest, the antenna isn’t either → gain asymmetry. Adjust rigging first.
- Cable run parallel to windlass cable. Inductive RF noise → noise in VHF transmit/receive. Always separate signal and power; cross at 90° if needed.
- No post-installation SWR test. SWR (Standing Wave Ratio) must be < 2:1 between VHF and antenna. If > 3:1, antenna or cable faulty; VHF at risk during long transmissions.
FAQ — VHF antenna in practice
1 m or 3 m whip antenna on a sailboat?
1 m is enough for cruising (gain ~3 dBi). 3 m adds ~6 dBi but catches more wind aloft. For racing, 1 m remains the majority choice (drag/range trade-off).
How long does a modern VHF antenna last?
Typically 10-15 years. Rubber/fiberglass ages slower than the connector electronics. The O-ring at the base is the weak point — inspect annually.
Separate AIS antenna from VHF antenna?
No. AIS Class B transmits on the same VHF channels 161.975/162.025 MHz, so one masthead antenna suffices for VHF + AIS-RXTX.
Is a lightning arrestor necessary?
Offshore tropical yes. Coastal France optional. Install the arrestor in the mast near the antenna. Cost ~150-300 € ex-VAT, installation 1-2 h.
Can I measure SWR myself?
Yes with a VHF SWR meter (Bird 43, Daiwa CN-901HP, ~200-400 € ex-VAT). Insert between VHF and antenna. Transmit on channel 16 at max power for 1 second, read SWR. If >2:1, there’s a problem.
3 real-world cases — VHF antenna installation
Case 1 — Sun Fast 3300 club racing sailboat
Masthead antenna Shakespeare 6225-R 1 m + RG213 cable 18 m + PL259 connectors greased with self-amalgamating tape. Total material cost: 280 € ex-VAT. Installation time: 4 h in dry dock during 2024 mast replacement. Post-install SWR measured: 1.3:1 on channel 16, compliant. Range to Carnac semaphore: 18 NM measured (16 NM theoretical).
Case 2 — Mini 6.50 — emergency backstay + masthead antenna
Dual antenna for redundancy in racing. Primary masthead + emergency backstay (tilting mast in case of dismasting). 2-position coaxial switch. Material cost: 580 € ex-VAT (2 Glomex RA1226 antennas + switch). Validation: Mini Transat 2025, no radio failure.
Case 3 — 8 m sailboat without mast (sloop dinghy)
2 m whip antenna on stern rail (Shakespeare 5400) + short RG213 cable 4 m. Material cost: 180 € ex-VAT. Practical range 7-9 NM against local Channel ferries. Acceptable limit for summer coastal use on the French Riviera.
Alternatives rejected — solutions not retained
- 3 m fiberglass antennas on stern rail: tempting to compensate for lost height (vs masthead). Theoretically +3 dB gain. In practice, windage while sailing upwind destroys the antenna within 2-3 seasons. Not relevant for sailboats under sail.
- Glomex Mini-Lock antenna (foldable): useful for passing under bridges. But 3-4 dB loss vs fixed full-length antenna. Consider only for lake/river navigation with mandatory low bridges.
- Dedicated balcony antennas for AIS: some cruisers buy a 2nd antenna for AIS to avoid overloading the main VHF antenna. Unnecessary — AIS Class B transmits on the same channels; one masthead antenna suffices.
- RG58 cable even if short: some think RG58 on 5-6 m is OK. False: loss is 1.5 dB/m, so 8-9 dB total = 85% of power dissipated. Always use RG213 minimum, regardless of length.
Annual maintenance — workshop checklist
VHF antenna maintenance — Skysat workshop
- Annual visual inspection: whip antenna not broken, O-ring watertight, stainless screws not loose.
- SWR meter check: measure SWR each season. If >2:1, disassemble and inspect connectors.
- Self-amalgamating tape on connectors to be renewed every 3 years (seawater slowly degrades the adhesive).
- RG213 cable: preventive replacement every 10-12 years. Dielectric ages, attenuation increases gradually.
- Periodic radio test: call channel 16 to nearby semaphore, confirm power and clarity. Do this before every offshore passage.
Skysat distributes Shakespeare, Glomex, and Mantagua antennas. This article reflects our experience installing VHF antennas on over 200 sailboats between 2018 and 2026. 2026 ex-VAT prices are distributor estimates.
