The essentials in 30 seconds
- VHF range ∝ √antenna height. Doubling the height does not double the range — Norton 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 signal station (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 (dinghy, etc.), 2 m high antenna on stern rail 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.
The 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. A budget VHF with a properly installed antenna = manufacturer’s 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 — 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, 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 (masthead antenna 17 m) to cargo ship (antenna 35 m): 1.22 × (4.12 + 5.92) = ~ 12 NM.
- Sailboat (masthead antenna 17 m) to signal station (antenna 80 m): 1.22 × (4.12 + 8.94) = ~ 16 NM.
- Sailboat (stern-rail antenna 2 m) to same signal station: 1.22 × (1.41 + 8.94) = ~ 12.6 NM... in theory. In practice, wave masking (the antenna is hidden by the crest) reduces usable range to 5–8 NM.
The key isn’t just maximum range — it’s 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 created by the wind transducer or mainsail.
- Type: 1 m rubber/fiber 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 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.
The extra cost of RG213 vs RG58 = €2–3/m. Over 20 m of 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 always be protected (self-amalgamating tape + silicone grease).
- N (Type N): professional/military standard. Native watertightness (O-ring), tightened with a wrench. More expensive, less common in cruising.
Critical junctions:
- Mast base: the junction where the cable exits the mast and meets the 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 signal station | Ex-VAT cost |
|---|---|---|---|---|
| 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 common installation errors
Antenna errors — Skysat workshop
- RG58 cable inside the mast. Ridiculous savings, 60–70% range lost. Always use RG213 minimum.
- No self-amalgamating tape at mast base. Seawater infiltrates the connector, causes shorts. Intermittent failures are hard to diagnose.
- Antenna not straight (permanent rig heel). If the mast isn’t vertical at rest, the antenna isn’t either → gain asymmetry. Rig must be tuned 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. In racing, 1 m remains the majority choice (drag vs range trade-off).
How long does a modern VHF antenna last?
Typically 10–15 years. Rubber/fiber 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 the same antenna suffices. On combined VHFs (B&G V60-B), a single masthead antenna covers both VHF and AIS-RXTX.
Is a lightning arrestor needed?
Offshore tropical yes. Coastal France optional. Mount the arrestor inside 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 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 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 signal station: 18 NM measured (16 NM theoretical).
Case 2 — Mini 6.50 — emergency backstay + masthead antenna
Dual antenna for racing redundancy. Primary masthead + emergency on 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 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 ruled out — solutions not retained
- 3 m fiber 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 low bridges. But 3–4 dB loss vs a full-length fixed 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 a 5–6 m RG58 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 intact, 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 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 a nearby signal station to 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 indicative of authorized distributor rates.
