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 against a shore 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 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 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 connections.
The VHF antenna is the component that turns your radio into a useful safety tool. A top-end VHF (B&G V60-B, Raymarine Ray73) with a poorly installed antenna = range cut by 4. An entry-level VHF with a correctly 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. 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 travels in a straight line (near-optical). It does not bend around Earth’s curvature or penetrate 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 shore station (antenna 80 m): 1.22 × (4.12 + 8.94) = ~ 16 NM.
- Sailboat (stern-rail antenna 2 m) to same shore station: 1.22 × (1.41 + 8.94) = ~ 12.6 NM... in theory. In practice, wave masking (the antenna sits low in the trough) drops useful range to 5–8 NM.
The issue isn’t just maximum range; it’s practical range in real conditions: rough seas + boat obstructions (bimini, adjacent mast, solar panels). The higher the antenna, the cleaner the signal leaves the boat’s environment.
Masthead antenna — technical detail
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 over 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.
- Sailboat without mast: dinghy, sailboat with tilting mast, large RIB.
- Dinghy: portable antenna connected to a handheld VHF when needed.
As a primary antenna, the stern-rail antenna limits 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 RG213 vs RG58 = €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 + marine 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: 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 screws greased.
- VHF rear: connection to the radio’s antenna output. Check tightness annually.
Comparative table of configurations
| Configuration | Antenna height | Cable | Range to shore 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 mistakes
Antenna errors — Skysat workshop
- RG58 cable inside the mast. Ridiculous saving, 60–70% range loss. Always RG213 minimum.
- No self-amalgamating tape at mast base. Water infiltrates the connector, causes intermittent shorts. Hard to diagnose failures.
- Antenna not vertical (permanent rig heel). If the mast isn’t plumb at rest, the antenna isn’t either → gain asymmetry. Rig must be tuned first.
- Cable run parallel to windlass cable. RF noise induction → noise in VHF TX/RX. Keep signal and power separate; cross at 90° if needed.
- No post-installation SWR check. SWR 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 the norm (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. Mount arrestor 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 max power 1 sec, read SWR. >2:1 = problem.
3 real-world cases — VHF antenna install
Case 1 — Sun Fast 3300 club racing sailboat
Masthead antenna Shakespeare 6225-R 1 m + RG213 cable 18 m + PL259 connector greased with self-amalgamating tape. Total material cost: €280 ex-VAT. Installation 4 h in dry dock during 2024 mast step. Post-install SWR measured: 1.3:1 on channel 16, compliant. Range to Carnac shore 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 dismasting scenario). 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. Material cost: €180 ex-VAT. Practical range 7–9 NM against local ferries in the Channel. Acceptable limit for summer coastal use on the French Riviera.
Alternatives rejected — solutions not retained
- 3 m fiberglass antenna 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 low bridges. But 3–4 dB loss vs fixed full-length antenna. Consider only for lake/river sailing with mandatory low bridges.
- Dedicated balcony antennas for AIS: some cruisers buy a second 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 when short: some think RG58 over 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 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 shore 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.
