Marine HF Radio Antennas, 2 to 30 MHz

Mast or Side Mount Antenna Models HM218/M and HM223/M

Antenna models HM218/M and HM223/M are suitable for all HF marine radio communications in the 2 to 30 MHz frequency range. These longer antennas offer top performance together with a two-piece light weight construction enabling easy dismantling and storage.

The antennas are designed to couple with transmitters via an Antenna Tuning Unit (ATU).

• HM218/M stands 6.4 metres tall when fully assembled and can handle up to 500 watts input power.
• HM223/M is taller at 8.1 metres and is rated for 1,400 watts power.

Twin braided copper radiators are sealed inside the fibreglass radome and terminate on a band approximately 50 mm above the top of the stainless steel support tube to which the high voltage feed cable attaches via a welded 6 mm bolt. Mount tubes do not carry RF voltage.

To broaden your choice of mounting positions, both mast mount and side mount options are available.

For mounting to a mast, 2 x UAM180L galvanised steel parallel clamps are recommended for a round mast between 40 mm and 75 mm in diameter.

Side mounts are nylon and include ½"–BSW stainless steel fasteners. These allow easy mounting to the side of a wheelhouse or any other vertical flat surface. Order NSM218 or NSM223 according to the antenna model. 2 nylon side mounts are necessary. Drill a 12.7 mm (½") diameter hole through the wall for the stainless steel bolt and then firmly secure each side mount in position.

Deck Mount Antenna Model HM300

HM300 is a 10 metre tall free standing marine HF radio deck mount antenna specifically designed for larger vessels. This model delivers outstanding performance, is very durable and accepts high input power up to 2,000 watts PEP.

The antenna couples with a transmitter via an Antenna Tuning Unit (ATU).

The sturdy fibreglass radome is a three piece construction with each section joined with stainless steel ferrules. The radome tip has a corona ball to prevent high voltage discharge into the atmosphere.

The antenna butt is bonded to a short piece of stainless steel tube. This is located into a very sturdy stainless steel deck mount plate.

The vertical mount tube is welded to a 300 mm round, 12mm thick stainless steel plate. Deck mounting is via 4 holes in the plate and termination is via a 6 mm bolt at the lower base. Radiating elements are encased inside.

Deck Mount Antenna Models HM212 and HM215

The HM212 and HM215 deck mount antenna models are suitable for all HF marine communications in the 2 to 30 MHz frequency range.

• HM212 is 3.7 metres tall.
• HM215 is 4.5 metres tall.
• Both antennas deliver 2.1 dBi gain and are rated for up to 250 watts power.

These antennas are designed to couple with transmitters via Antenna Tuning Units (ATU). Clients contemplating purchase of these antennas should verify with their supplier whether their ATU specification will load the given length of radiator for the chosen model at the lowest frequency desired.

Radiators are sealed inside the single piece white fibreglass tapered radome and terminate via 5 metres of high voltage (20 kV) feed cable side exiting from the chromed brass mount ferrule.

Both models come complete with our highest quality fully stainless steel MM2 folding deck mount. This base folds down in two directions and also swivels in the opposite plane by loosening the stainless steel pivot bolt. This versatility allows the antenna to be mounted in a variety of positions on any flat surface and at any angle using four screws or bolts.

The antenna must be in a vertical position for best performance and can be folded down flat when not required.

HF marine antenna installation advice

The vertical radiation pattern for these installations is largely influenced by the size, shape and nature of the ground plane under the antenna.

The length and placement of the feedline also has a large effect on pattern formation, with modelling indicating a long feedline at right angles to the antenna causing pattern to vary greatly from omnidirectional.

As every installation is different, no radiation patterns are published for these antennas. In all installations a good earth system is an essential key to good performance.

In simpler marine installations, including the case of fibreglass hulls, radiation may also occur from earth leads. Keep all leads as short as posible and joints in the earth system fully soldered. Your earthing system may need more planning and attention than your vertical radiator ! Earthing system problems may also cause the DC feed wiring to become an active radiator.

It is wise to verify in advance the ability of your ATU or autotuner to match shorter radiators at the lowest frequency. Symmetrical, balanced, as well as low resistance earthing is needed for good omnidirectional radiation. Cable feed to antenna from the tuner that is not assisting symmetrical pattern formation by being at right angles to the antenna must be minimised.