Frequently Asked Questions about Marine TV Antennas
 

Q. Isn't it, the higher the gain the better?

A. Of course you need high gain especially in fringe areas but not at the expense of causing other problems such as overdrive distortion and intermod. Quality marine antennas provide sufficient gain for most conditions and are carefully constructed with hand tuned filters to reduce intermod and distortion to a minimum. Remember that Maximum gain is usually achieved with a compromise to performance in other areas. It looks better on the spec sheet than the picture on your set.

Q. Why quality marine antennas use hand tuned filters?

A. Filters help reduce interference from other transmitters in the area. You own or a nearby Marine VHF Radio for instance. Quality marine antennas have special filters to reduce this potential for interference. There are also filters to reduce interference from FM stations and Two-way radio stations and Paging Transmitters. A technician adjusts each filter manually while using a Network analyzer to view the filters passband to insure razor sharp interference rejection.

Q. What is the main cause of failure with marine antennas?

A. Water entry: either by storing the antenna upside-down and allowing standing water to creep in, or by water creeping up the coax cable through capillary action. Quality marine antennas are usually well sealed and injected with poly-urethane foam but standing water in the mounting flange can creep inside over time. Lightning also damages a few antennas every year. Good marine antennas have a static discharge protection circuit but it will not protect from a direct lightning hit. Warranty does not cover damages from Lightning or Water entry.

Q. How can I protect my antenna from water entry?

A. Use the continuous low loss coaxial cable normally supplied with the antenna. If a splice is necessary, make sure that you seal the splice completely with "Coax-Seal". Electrical tape or shrink tubing does not provide a waterproof seal.

Q. What happens when water enters the coax cable?

A. There is a DC voltage on the cable to power the antenna's internal amplifier. When the splice gets wet, it allows current to flow and electrolysis quickly destroys the soft copper center conductor of the coax cable where it meets with the connector. In tests, we have seen this action take place in as little as 30 minutes. The splice connectors may then need to be replaced. If you must splice, use coax-seal or Liquid Tape to seal against water entry.

Q. Why good marine antennas use separate amplifiers for VHF and UHF TV?

A. The two frequency bands are quite different and require different types of circuits and transistors for optimum performance. Competitive systems use a single amplifier to cut costs though they also cut performance. Using separate amplifiers also reduces the chance of interference on one band, spilling over to the other.

Q. What about damage from the Sun in Southern Latitudes?

A. Quality marine antenna radomes are made of thick high impact ABS plastic with Korad UV inhibitors which will protect the antenna from yellowing and plastic degradation for many years. Thousands of well-known brand marine antennas have been in continuous service in excess of 10 years without any sign of sun damage.

Q. What about problems with vibration?

A. In our early years this was a problem but now antennas have much thicker ABS plastic with a stiffening pattern and we inject all antennas at the final production stage with polyurethane foam to further stiffen the antenna and to protect the circuit board inside. The foam also acts as a moisture barrier.

Q. Where should I mount my antenna?

A. In the clear and as high as is practically possible. Range is strongly influenced by the height of both the TV station antenna and the vessel's antenna.

Q. Should I use a Rotor with my antenna?

A. As alternative yes, especially if your vessel is more at pear then at sea. However, mostly all marine antennas are Omni-directional, which means they see equally well in all directions without being turned.

Q. How many TV sets can I connect to my antenna?

A. The small antenna systems will feed two TV sets or one TV set and one FM radio. The bigger more element antenna systems will also feed an AM Radio and it covers the short-wave AM band as well as the Broadcast AM band. If there are several sets on board, consider using one of our combination power box/amplifiers which will feed up to 8 TV sets. For larger systems and higher performance, consider antenna systems combination with power box, amplifiers, filters and branch outputs used on Merchant Ships, Cruise Liners and by the Navy. They work with Banded Amplifier System and can feed over 1000 TV sets.

Q. What about supply voltages?

A. Mostly all marine antenna systems can be powered by 12-24VDC or 110-220VAC

Q. How can I tell if my antenna is working or not?

A. Turn off power to the system. The picture quality should show severe degradation.

Q. What causes ghosting?

A. Not all signals reach an antenna directly. They can be reflected by buildings, water towers, mountains, or bodies of water. These reflected signals arrive at the antenna microseconds after the direct signal. This causes a second, fainter image to appear on the TV screen just to the right of the main image. This is called a trailing ghost. It can often be eliminated by moving to another location.