The essentials in 30 seconds
- VHF range ∝ √antenna height. Doubling the height does not double the 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 against 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 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 chatterton at mast-deck junctions. #1 cause of VHF failures in cruising: wet connectors.
Your VHF antenna is what turns your radio into a useful safety tool. A top-tier VHF (B&G V60-B, Raymarine Ray73) with a poorly installed antenna = range cut by 4. An entry-level VHF with a properly installed antenna = manufacturer-rated range. The difference isn’t in the radio; it’s in the antenna.
For the VHF itself, see our Fixed vs portable VHF + AIS Class B for sailboats. 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 major 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, angle loss (waves masking the antenna) reduces usable range to 5–8 NM.
The real issue isn’t maximum range but practical range in real conditions: rough seas + intermediate obstructions (bimini, 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 vane or mainsail.
- Type: 1 m rubber/fiberglass whip, gain 3–6 dBi, omnidirectional.
- Brands: Shakespeare, Glomex, Mantagua. Typical price: €80–180 ex-works.
- Connection: PL259 male at base, RG213 or Belden 9913 coaxial cable inside the mast.
- Watertightness: O-ring at the base + self-amalgamating chatterton 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, low-mast sailboats, 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.
The RG213 vs RG58 surcharge = €2–3/m. Over 20 m mast, that’s €40–60 ex-works 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 chatterton + silicone).
- N (Type N): pro/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 chatterton + silicone.
- Masthead: O-ring under the antenna, greased stainless screws.
- VHF rear: connection to the radio’s antenna output. Tighten annually.
Comparative table of configurations
| Configuration | Antenna height | Cable | Range to semaphore | Ex-works budget |
|---|---|---|---|---|
| Masthead + RG213 | 17 m | RG213 (18 m) | 16 NM theoretical, 14 NM practical | ~ €350 ex-works (antenna + cable + connectors) |
| Masthead + Belden 9913 | 17 m | Belden 9913 (18 m) | 16 NM theoretical, 15 NM practical | ~ €450 ex-works |
| Masthead + RG58 | 17 m | RG58 (18 m) | 16 NM theoretical, 10 NM practical (cable losses) | ~ €280 ex-works (not recommended) |
| Stern rail + RG213 | 2 m | RG213 (5 m) | 12.6 NM theoretical, 5–8 NM practical | ~ €250 ex-works |
| Backstay + RG213 | 14 m | RG213 (15 m) | 15.5 NM theoretical, 12 NM practical | ~ €330 ex-works |
5 common installation errors
Antenna errors — Skysat workshop
- RG58 cable in the mast. Ridiculous savings, 60–70% range loss. Always RG213 minimum.
- No self-amalgamating chatterton at mast base. Water infiltrates the connector, causing shorts. Intermittent failures hard to diagnose.
- Antenna not straight (permanent rigging heel). If the mast isn’t vertical at rest, the antenna isn’t either → gain asymmetry. Tune the rigging first.
- Cable run parallel to windlass cable. Inductive RF noise → noise in VHF TX/RX. Always separate signal and power; cross at 90° if needed.
- No post-installation SWR check. 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. 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 O-ring at the base 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 arrestor in mast near antenna. Cost ~€150–300 ex-works, installation 1–2 h.
Can I measure SWR myself?
Yes with a VHF SWR meter (Bird 43, Daiwa CN-901HP, ~€200–400 ex-works). Insert between VHF and antenna. TX on channel 16 max power for 1 sec, read SWR. >2:1 = problem.
3 real-world workshop cases — VHF antenna install
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 chatterton. Total material cost: €280 ex-works. 4 h installation during 2024 mast step. 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-works (2 Glomex RA1226 antennas + switch). Validation: Mini Transat 2025, no radio failures.
Case 3 — 8 m sailboat without mast (dinghy sloop)
2 m whip antenna on stern rail (Shakespeare 5400) + short RG213 4 m. Material cost: €180 ex-works. Practical range 7–9 NM against local Channel ferries. Acceptable limit for summer coastal use on the French Riviera.
Alternatives ruled out — 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 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 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 when short: some think RG58 over 5–6 m is OK. False. Loss is 1.5 dB/m, so 8–9 dB total = 85% of power dissipated. Always RG213 minimum, regardless of length.
Annual maintenance — workshop checklist
VHF antenna maintenance — Skysat workshop
- Annual visual inspection: whip antenna intact, O-ring watertight, stainless screws tight.
- SWR meter check: measure SWR each season. If > 2:1, disassemble and inspect connectors.
- Self-amalgamating chatterton on connectors to be redone 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 to 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-works prices are indicative of authorized distributor rates.
