Electrical

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The loss in RF coaxial cable increases substantially and quickly, when there is water intrusion. Coax that uses foam dielectric, like RG8X and LMR type coax, is particularly prone to this problem because the water can quickly propagate along the foam dielectric used in these type coaxes.

Recreational marine VHF antennas are usually broken down into three categories: 3- and 4-foot sailboat antennas (3dB gain), 8-foot powerboat antennas (6 dB gain) and 16-plus-foot, long-stick antennas (9+ dB gain) that are popular on larger, long-range craft. Antenna gain is a ratio related to an antennas effective radiated power (ERP) instead of a fixed quantitative value.

No one really wants just practical gifts, so weve tried to locate a few items that go beyond pure utility for this holiday season.

Keeping batteries fully charged is a science that cruisers have to master sooner or later. If todays high-capacity AGM batteries arent managed properly, valuable amp hours in can permanently trickle away through sulfation, as we saw in our test of AGM batteries (See Fighting Sulfation in AGMs, PS May 2015). Good battery management means complete re-charging that matches the charging profile of your battery, and this means an accurate sensing of battery voltage. As we saw in our recent report on battery monitors (see Best Battery Monitor Test Update, PS October 2017) a good monitor will also keep track of temperature, as this can be a limiting factor in charge acceptance rate.

Our test focused primarily on the small-wire connections tensile strength, with and without solder, but we also looked at their durability under tough environmental conditions. We tested the pull-out strength without solder and the pull-out strength of soldered connections at 400 degrees by heating the connections in an oven to simulate overheating conditions. We tested fatigue by spinning a 6-inch length of splice wire at 650 RPM in a simple device that we called the wire-fatigue whirligig. Finally, testers soaked all samples for four months in salt water to accelerate corrosion, and then, we repeated the fatigue test.

Two recent tests graphically demonstrated the importance of monitoring state of charge in a boats batteries. hese tests demonstrated that a sealed batterys capacity will be reduced over time, if its never brought back up to a full state of charge. But just how accurate are the monitors we use to gauge our batteries states of charge?

Our test gear comprised a ProMariner ProNautic 12-40P battery charger; West Marine-branded, flooded-cell, deep-cycle battery with a 75-amp hour rating; and two 120-volt, 70-watt incandescent light bulbs powered through a Heart 140-watt DC to AC inverter. This setup created a 12-amp DC load on the battery. We confirmed voltage and current draw using a Fluke Model 867B graphical meter and a Blue Sea Systems Model 8110-amp clamp/multimeter.

In our recent test of absorbed glass mat (AGM) batteries, we cycled five different batteries through 30 deep cycles to 11.7 volts but only partially recharged them for one hour after each discharge cycle at a charge rate of 46 percent of battery amp-hour capacity. (See PS May 2015 online.) The object of the exercise was to demonstrate just how quickly sulfation, which is caused by keeping a battery in a partial state charge (PSOC), can reduce the capacity and eventually permanently ruin a good battery.

Our May 2015 report on absorbed glass mat (AGM) batteries got us thinking about wet cell-batteries. While it is easy to find distilled water suitable for topping off the battery electrolyte in the U.S., what happens when we are not near a reliable supply? Are there any substitutes? What should we avoid?