.
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. Naval 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.

The PR-414 pictured here is the result of painstaking engineering and the use of state of the art components including high performance GaAs Hetrerojunction Bipolar Transistors and MMIC devices.

A. Filters help reduce interference from other transmitters in the area. You own or a nearby Marine VHF Radio for instance. Naval 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. Our smallest antenna has 11 separate filter adjustments.

Q. What is the main cause of failure with Naval 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. Our antennas are well sealed and injected with poly-urathane foam but standing water in the mounting flange can creep inside over time. Lightning also damages a few antennas every year. Our antennas have a static discharge protection circuilt but it will not protect from a direct lightning hit. Warranty does not cover damages from Lightning or Water entry. Naval antennas now made in the USA have a one year replacement warranty and a 10 year pro-rated warranty.

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

A. Use the continuous low loss coaxial cable 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 co-ax 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 electrolisis 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. We have both in stock.

Q Why does Naval 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. Naval 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 Naval brand 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 our US made 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. Naval antennas are common the world over on tugs and workboats where engine vibration is quite severe and constant 24 hours a day in many cases.

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. A rotor is not necessary and would not provide any increase in performance. Naval 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 PR-411 and PR-414 will feed two TV sets or one TV set and one FM radio. The PR-414 will also feed an AM Radio and it covers the shortwave 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 our PR-420 and PR-422 antennas as used on Merchant Ships, Cruise Liners and by the Navy. They work with our Banded Amplifier System and can feed over 1000 TVsets.

Q. What about supply voltages?

A. Naval has power supplies to cover 12-24vdc, 110-120vac and 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.

Q Can I use this antenna on my RV?

A. Omni-directional antennas are commonly used on RV's however at this time our mounting arrangements are designed for use on boats and may not adapt easily to your RV unless it can accept a 1.5 inch pipe mount.

Q. Can I use this antenna on my home?

A.  Yes an omni-directional antenna can be used on a house but if fringe reception is required, a directional antenna pointed at the fringe station will give better performance.

Q. What about Rabbit Ears on a boat?

Rabbit ears work quite well at home as they are adjusted for direction and for the channel of concern and they are actually very efficient for their size and low cost.. When one changes channels however, the rabbit ears must change direction and also be made shorter or longer to optomize reception for the new channel. Dockside they will will perform too but as an inside antenna they are subject to signal blockage by the structure of the boat.  The downside is that they must be continually adjusted while underway or swinging at anchor due to the directional characteristics. They are also optomized for one channel. This presents obvious problem on a moving vessel thus the reason for omini-directional antennas at sea.

.
.

 Home | Navy | Work Boats | SatTV  | Site Map | News | Help | Drawings | Catalog/Prices | Ships

 
copyright © 1997-2018