Maritime Mobile Operation on LF May be a First for Amateur Radio

What began as a “let’s-see-if-we-can-do-this” effort resulted in successful Amateur Radio contacts on 475 kHz in early August by two Canadian operators aboard the sailing vessel Hakuna Matata off the coast of British Columbia. The accomplishment may be an Amateur Radio first. Mark Mattila, VA7MM, and Toby Haynes, VE7CNF, equipped Mattila’s 31-foot offshore-equipped Beneteau sloop with the gear necessary to make LF maritime mobile operation possible. The vessel already had a 46-foot mast with an insulated backstay antenna for marine and ham radio communication.

Haynes designed the overall system, and work done on the vessel prior to the sailing season facilitated the radio experiments. This included installing new batteries, a new RF ground system braid and counterpoise conductors, and an antenna for 2-meter FM communication. Before the Hakuna Matata set sail, word went out among the local 630-meter community to be listening for CF7MM/mm on 475 kHz CW.

Haynes fabricated a 630-meter linear transverter for the project. Its bidirectional high-power mixer circuit that takes full RF output from an Icom IC-746PRO transceiver operating at an IF of 1.9 MHz and mixes with a local oscillator at 1.5 MHz down to 475 kHz. For receiving, signals pass in the other direction are upconverted to 1.9 MHz, with some minor signal attenuation.

Perhaps more critical were the antenna and RF grounding systems. The actual radiating element was a 38-foot long piece of #14 wire attached to the highest point on the mast. Grounding was accomplished by using the vessel’s cast-steel keel and a couple of 30-foot wires near the gunwales. Tuning and matching were achieved using a loading coil and variometer, involving a total of 1,120 μH of inductance. Operation was coordinated using a South Coast 2-meter FM repeater, and the 630-meter operation was scheduled for late morning and early evening. The propagation mode was ground wave.

Contacts were made while the vessel was at anchor in Boho Bay, Silva Bay, and Winter Cove. Stations worked on CW included VE7SL on Mayne Island, VE7BDQ in Delta, VE77VV in Victoria, VE7CA in North Vancouver, and VA7JX in Campbell river. VE7SL and VE7VV also were worked on 630 meters on SSB. The “best DX” was a contact from Silva Bay with VA7JX spanning 142 kilometers (about 88 miles).

Mattila and Haynes said they were impressed by the signal reports received, given the transmitter’s estimated 160 mW EIRP. “Received signals from participating stations varied from S-1 to S-9 +10 dB, and copy was easy for all contacts,” they said.

The yet-to-be-implemented US Amateur Radio regulations governing operation on 630 meters do not permit mobile operation.

Source:ARRL

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