Maritime mobile amateur radio
Maritime Mobile Nets
Many long-standing and sophisticated radio nets are regularly operated by shore-based amateur volunteers for seafaring operators.
Maritime mobile amateur radio nets
Frequency (MHz)
Time(s) (UTC)
Operator(s)
Notes
Transatlantic maritime mobile net
21.400
1300
Trudi (8P6QM)
Based in Barbados, Atlantic crossing
Worldwide weather net
21.303
1300
Neville (G3LMO), Richard (KT4UW), Don (6Y5DA)
UK maritime mobile net
14.303
0800 1800
Bill (G4FRN), Bruce (G4YZH), Tony (G0IAD) and others
Mississauga maritime net
14.121
1145
Doug (VE3NBL), Ernie (VE3EGM)
Based in Canada, Atlantic crossing
Caribbean maritime mobile net
7.241
1100
Lou (KV4JC)
Caribbean cruising
Caribbean weather net
7.086
1120
George (KP2G)
Caribbean weather information
INTERMAR German maritime mobile service net
14.313
1630
Rolf (DL0IMA)
daily all Oceans
The Maritime Mobile Service Network
14.300
1700-0200 (winter) 1600-0200 (summer)
Net Manager is Rene (K4EDX) with over 70 net controllers
Atlantic, Caribbean and E. Pacific with hourly WX report. Position reports posted upon request. See our web page
Note: Information dated 2000 – Mistweb entries South, East-west, West-east; and www.intermar-ev.de
Technical considerations
There are some special considerations when installing and using amateur radio transmitters and receivers afloat. These include power supply, RF earthing, antenna design and EMC (Electromagnetic compatibility) with other electronic equipment aboard.
Antenna design and installation
For MF and HF use, the most common antenna design is to add two RF insulators into the backstay of the mast and feed it from the transceiver using a sintered bronze earthing plate, bolted to the outside of the hull, well under the waterline, as an earth. On metal hulled boats the earthing plate can be dispensed with, and the whole hull used as a ground. In this case, the thickness of any paint layer is entirely negligible at RF.
On a yacht with twin backstays, if insulators are placed in both of them and they are fed from the mastead, they may be usable as an ‘inverted vee’ avoiding the need to feed the antenna against ‘ground’.
Either format will require the use of an ATU (Antenna Tuning Unit) to achieve resonance for the HF frequency in use, as the physical length of the antenna will almost invariably be incorrect at the frequency of choice.
A few twin-masted sailing vessels have the space to erect a “Tee” antenna or an inverted “L” between masts. These antenna configurations are more common on merchant ships.
For VHF and UHF operation, one option is to mount a small yagi antenna to a pole 1-2 m (3-6 ft) long and haul this to the masthead using a flag halyard. If the halyard is correctly knotted to the middle and bottom of the pole, it is easy enough to make the antenna project above the clutter at the masthead into clear air. The problem is in rotating it – it usually needs to be lowered and re-raised to alter the direction of its beam. For the safety of masthead fittings and lights it is better if these yagis are light in weight and made largely of, for example, plastic tubes supporing internal wire conductors. Operating in this way is best reserved for when in harbour or at anchor, to avoid interfering with the operation of the boat. Repeated loss of signal due to rolling and pitching would make it impractical for useful communication at sea anyway.
For FM operation on the 2 m band, the masthead vertical whip that is normally installed for marine VHF operation will provide good omni-directional vertically polarised signals. The frequency of operation around 145 MHz is close enough to the antenna’s design frequency of 156 MHz that most amateur tranceivers will not need an ATU and will not suffer unduly from a poor (high) SWR.
References
^ “KV4JC”. qrz.com. http://www.qrz.com/db/. Retrieved 2009-11-08.
See also
Amateur radio
Marine and mobile radio telephony
Roberts Bank Lifeboat, Delta BC – Equipped with amateur radio
Satellite Internet access
v d e
Two-way radio
Amateur and hobbyist
Amateur radio Amateur radio repeater Citizens’ band radio Family Radio Service General Mobile Radio Service Mobile rig Multi-Use Radio Service PMR446 LPD433 UHF CB (Australia)
Aviation (aeronautical mobile)
Air traffic control Aircraft emergency frequency Airband Mandatory frequency airport Single Frequency Approach UNICOM
Land-based commercial and government mobile
Business band Base station Mobile radio Professional Mobile Radio Radio repeater Specialized Mobile Radio Trunked radio system Walkie talkie
Marine (shipboard)
2182 kHz 500 kHz Coast radio station Marine VHF radio Maritime mobile amateur radio
Signaling / Selective calling
CTCSS Dual-tone multi-frequency D-STAR MDC-1200 Push to talk Quik Call I Quik Call II Selcall
System elements and principles
Antenna Audio level compression Automatic vehicle location APRS Call sign CAD DC remote Dispatch Fade margin Link budget Rayleigh fading Tone remote Voice procedure Voting (diversity combining)
Categories: Amateur radio
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