The essentials in 30 seconds
- VHF range ∝ √antenna height. Doubling the height does not double the range — Norton formula: range NM ≈ 1.22 × √(antenna_h_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 sailboats without a mast (dinghy sloop, etc.), a 2 m high stern rail antenna is sufficient. 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 is 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 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 properly 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 on 156-162 MHz. At this frequency, the radio wave propagates in a straight line (near-optical). It does not bend around Earth’s curvature or pass through large metal obstacles.
Norton range formula (in NM):
range ≈ 1.22 × (√h_transmitter + √h_receiver), heights in meters.
- Sailboat (17 m masthead antenna) to cargo ship (35 m antenna): 1.22 × (4.12 + 5.92) = ~ 12 NM.
- Sailboat (17 m masthead antenna) to coast guard station (80 m antenna): 1.22 × (4.12 + 8.94) = ~ 16 NM.
- Sailboat (2 m stern rail antenna) to the same coast guard station: 1.22 × (1.41 + 8.94) = ~ 12.6 NM... in theory. In practice, wave masking (the antenna is hidden by waves) reduces usable range to 5-8 NM.
The key is not 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 a mast: dinghies, boats with tilting masts, high-power RIBs.
- Dinghy/tender: portable antenna connected to a handheld VHF when needed.
As a primary antenna, the stern rail 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 cost difference = 2-3 €/m. For 20 m mast, that’s 40-60 € ex-VAT — 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 + marine silicone).
- N (Type N): professional/military standard. Native watertightness (O-ring), tightened with a wrench. More expensive, less common in cruising.
Critical junctions:
- Mast base: junction between cable exiting the mast and deck cable is exposed to seawater. PL259 + self-amalgamating tape + silicone.
- Masthead: O-ring under the antenna, stainless steel screws greased.
- VHF rear: connection to the radio’s antenna output. Check tightness annually.
Comparative table of configurations
| Configuration | Antenna height | Cable | Range to coast guard station | 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 in the mast. Ridiculous savings, 60-70% range loss. Always RG213 minimum.
- No self-amalgamating tape at mast base. Water infiltrates the connector, causes shorts. Intermittent failures hard to diagnose.
- Antenna not vertical (permanent rig 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. RF noise → noise in VHF TX/RX. Always separate signal and power; cross at 90° if needed.
- No post-installation SWR check. SWR must be < 2:1 between VHF and antenna. If > 3:1, faulty antenna or cable; VHF at risk on 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. Racing: 1 m remains standard (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 mast base O-ring is the weak point — inspect annually.
Separate AIS antenna from VHF?
No. AIS Class B transmits on the same VHF channels 161.975/162.025 MHz, so one antenna suffices. On combined VHFs (B&G V60-B), a single masthead antenna handles VHF + AIS-RXTX.
Is a lightning arrestor needed?
Offshore tropical yes. Coastal France optional. Mount in mast near 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. TX on channel 16 at max power for 1 second, read SWR. >2:1 = problem.
3 real-world workshop cases — VHF antenna install
Case 1 — Sun Fast 3300 club racing sailboat
Masthead Shakespeare 6225-R 1 m whip + RG213 18 m cable + PL259 connectors greased with self-amalgamating tape. Total material cost: 280 € ex-VAT. Installation time: 4 h dry dock during 2024 mast step. Post-install SWR measured: 1.3:1 on channel 16, compliant. Range to Carnac coast guard station: 18 NM measured (16 NM theoretical).
Case 2 — Mini 6.50 — emergency backstay + masthead antenna
Dual antenna for racing redundancy. 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 (dinghy sloop)
2 m whip antenna on stern rail (Shakespeare 5400) + short RG213 4 m cable. Material cost: 180 € ex-VAT. Practical range 7-9 NM against local Channel ferries. Acceptable limit for summer Mediterranean coast use.
Alternatives rejected — solutions not considered
- 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 in 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 AIS antennas on stern rail: 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 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% power dissipated. Always 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 steel 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 coast guard station, confirm power and clarity. Do 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 indicative of authorized distributor rates.
