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Navigation & Communication
VHF and UHF Radio Systems
VHF and UHF radio systems carry day-to-day voice traffic on and around an offshore unit. Marine VHF talks to supply and standby vessels, and on-board UHF links the bridge, drill floor, crane cabs and deck crews. The sub-Category covers fixed marine VHF sets with DSC, handheld radios, intrinsically safe handhelds, repeaters, base stations and antennas.
Bands and what each does
- Marine VHF runs from 156 to 174 MHz. Channel 16 (156.8 MHz) is the distress and calling channel, and channel 70 carries digital selective calling (DSC).
- On-board UHF uses channels near 457.525 to 457.575 MHz and 467.525 to 467.575 MHz that the ITU Radio Regulations set aside for communication within one ship or unit. A repeater pairs the two halves so handhelds reach across the structure.
- Some units run digital private mobile radio, such as DMR or TETRA, on frequencies the coastal state licenses.
Helideck aeronautical radio uses its own band and approvals, covered under aviation radio systems. GMDSS portable VHF radios are covered under Emergency communication (GMDSS).
Configurations
A fixed VHF set with DSC sits on the bridge and in the radio room. Handhelds serve deck crews, and Ex-rated handhelds serve the drill floor, shaker house and other classified zones. Repeaters and base stations extend UHF coverage through steel decks and columns, sometimes with radiating cable in shafts and pontoons.
Key specifications
| Parameter | Why it matters | Typical classes or units |
|---|---|---|
| Band and channel plan | Legal use in your waters | Marine VHF, on-board UHF, licensed PMR |
| Channel spacing | Must match the existing fleet | 25 kHz or 12.5 kHz |
| Transmit power | Range and licence limits | Fixed marine VHF 25 W, with a 1 W low setting |
| Ex rating | Use in classified zones | Zone, gas group and temperature class |
| Mode | Interworking | Analogue FM, DMR, TETRA |
Standards and what a used radio must meet
The ITU Radio Regulations set the marine VHF channel plan in Appendix 18 and the on-board UHF channels. ITU-R M.493 defines DSC. A fixed VHF set fitted to meet SOLAS chapter IV is GMDSS equipment, approved under the IEC 61097 series and IEC 60945, and usually carries the wheel mark. A handheld used in a hazardous area must be certified under IEC 60079, typically as intrinsically safe, and the certificate covers the battery and accessories as well. A non-approved battery voids the rating.
Failure modes and inspection
- Handheld batteries lose capacity, and the battery is part of the Ex certificate.
- Antennas, coaxial cable and connectors corrode on deck, and high VSWR (voltage standing wave ratio) shows it.
- Ex housings, seals and belt clips crack.
- Channel programming and tone codes belong to the last installation.
A radio technician checks output power, frequency error, deviation, receiver sensitivity and VSWR with a service monitor. Inspect each Ex handheld's label and certificate number against the IECEx or ATEX register.
Documentation
- Type-approval certificates for fixed VHF DSC sets.
- IECEx or ATEX certificates for Ex handhelds, chargers and batteries.
- Programming files and the OEM software version.
- MMSI programming history for DSC sets.
Integration with your unit
Reprogram channels and tone codes to your channel plan with the OEM software and cable. DSC sets store the previous unit's MMSI, and some models allow only an authorised dealer to reset it. Check that repeaters match your UHF frequency pair, and that radio interfaces into the PA or intercom suit your system's audio levels and keying. Ex chargers usually sit outside the classified zone.
Refurbishment, used or surplus
Used handhelds of the model already in service extend the fleet without reprogramming everything. Unused surplus Ex handhelds are a good find, since they cost far more than standard ones. Fit new batteries from the OEM's approved list to any used Ex radio. Analogue radios are cheap, but check how long your unit will keep analogue channels.
Related equipment
Radio calls often patch into intercom and PA systems. Naventr can confirm with the Seller which Ex certificates and batteries come with the radios.
FAQ
Frequently asked questions
Which UHF frequencies are used for on-board communication?
The ITU Radio Regulations set aside channels near 457.525 to 457.575 MHz and 467.525 to 467.575 MHz for on-board communication, with extra 12.5 kHz channels between them. National rules apply in territorial waters, so check the coastal state's plan.
Can I use a non-Ex radio on the drill floor?
No, any radio used in a classified zone such as the drill floor or shaker house must carry an ATEX or IECEx rating for that zone, gas group and temperature class. The battery and accessories must also be the approved types listed on the certificate.
Can a used marine VHF radio be reprogrammed for another unit?
Yes, most can be reprogrammed with the OEM software and cable. DSC sets also need the old MMSI cleared and yours entered, and some models allow only the OEM or an authorised dealer to reset the MMSI.
Do I need to replace the batteries on used intrinsically safe radios?
Plan on it, since battery capacity drops with age and only the battery types on the Ex certificate keep the rating. Buy new batteries from the OEM's approved list rather than relying on used packs of unknown age.
What should a radio technician test on a used VHF set?
A technician should measure output power, frequency error, deviation, receiver sensitivity and antenna VSWR with a service monitor. On DSC sets, also send a test call and confirm the MMSI and position input work.
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