Marine Antennas, TV,VHF & Other
Imtra - Marine Electronics

Electronics

Boat Accessories - Electronics

A large selection of marine TV antennas, VHF, mounts and Antennas accessories, high-quality strong construction antennas Imtra's, Lifetime Warranty. How ti Installing Antennas.

Imtra - Marine Antennas and Accessories

Contacts:

Imtra Corporation, 30 Samuel Barnet Boulevard, New Bedford, Massachusetts, 02745 USA Tel: (508) 995-7000 Fax: (508) 998-5359

www.imtra.com

TV Boat Antennas

Glomex TV Antennas
Standard equipment on finer sportboats and motor yachts, Glomex omnidirectional marine radio/TV antennas deliver superior performance on over-the-air TV broadcasts. Available as complete kits or as individual components to enable a customized solution for your boat or yacht. Imtra Glomex Marine Antenna Stainless Steel Pipe Mounting Bracket.

All Glomex products include a Lifetime Warranty.

- TV Glomex Antennas - 10 inch
TV Antenna Kits include antenna, amplifier and cables. Available with gain control, bypass or A/B switching amplifiers.

- TV Glomex Antennas - 14 inch
TV Antenna Kits include antenna, amplifier and cables. Available with gain control, bypass or A/B switching amplifiers. Or, choose the Community TV system for reception for up to 6 TV sets.

Conical Omnidirectional TV Antennas
The VEGA 4" conical TV antenna is compact and lightweight.

Dome Omnidirectional TV Antennas
Dome Boat Antenna 10" is compact and lightweight.

Altair 10" Dome TV Antenna with Bypass Amplifier and Nylon Mount.

Glomex VHF & Other Antennas
Choose from our broad selection of VHF, AM/FM, SSB, CB and Cellular marine radio antennas. Most feature UV resistant white nylon outer finish for a smooth, consistent long-lasting appearance and feel. Complete your system with mounts, extensions and accessories in stainless steel or high-impact synthetics.

All Glomex products include a Lifetime Warranty.

VHF Antennas - VHF antennas in a variety of lengths from 1-21.stainless steel or fiberglass strong construction.

Other Boat Antennas - specialty boat antennas for CB, AM/FM, Cellular and Single Side Band units.

VHF/Other Antenna Mounts - A large range of boat antenna mounts for surface, rail or masthead antenna installations. more >>

Other Mounts - A selection of specialty mounts for standard TV or VHF marine/boat antennas.

VHF/Other Accessories - coaxial cables, connectors, spitters for your boat antenna installation.

General Antennas Accessories
Deck fittings - allow antennas cables to pass cleanly through the deck.
Gaskets -to put between mounts and the deck.
Mounting Plate and Wedge Kits -
Wedge kits allow mounts to be mounted at angles for a good look and optimized performance.
Installation tools - for Glomex boat antennas.
VHF & TV Antennas for sale by Owner

VHF Antennas

How ti Installing Antennas


Your VHF antenna is an important component of your marine communications. Properly installed, your antenna will help maximize signal strength for clear reception and transmission. An improperly or poorly installed antenna, or one installed using inferior quality components, can result in signal loss or unreliable communications, neither of which will help you in an emergency. There are four important aspects to antenna installation: antenna location, the coax cable, the connectors, and the mounting.

The Location

Your antenna should be located more than three feet from your radio and as far away from metal objects and other antennas as possible to minimize signal interference and feedback. Since VHF signals travel in line of sight, mount your antenna as high as possible. VHF antennas on sailboats may be mounted at the top of the mast, especially if they are short stainless steel whips. Powerboat antennas should be above the deckhouse, flybridge, bimini top and all other structures. As most VHF antennas are fed with power from the bottom, the entire length of the antenna is an active radiator of transmission power. As a result, any portion of the antenna shielded by a mast, windshield or other obstruction will have little output, so locate the as much of the antenna as possible above or away from such impediments.

The Coaxial Cable

When you select a location for the antenna, be sure the run of the cable is as short and as straight as possible from the radio. Follow the manufacturer’s instructions as some antenna manufacturers provide coax that should not be cut or lengthened. In most cases it's Ok to shorten the cable supplied with the antenna as long as a minimum of seven feet is used.

If, on the other hand, your coax cable run is a long one, make sure the cable supplied with the antenna is long enough. If you need a longer cable, consider buying a new cable suited to the length of the run rather than cutting and splicing the cable supplied. Consult with an electronics specialist to assist you with determining the type of cable required as there are many factors involved in selecting a coaxial cable. Keep in mind that your cable and radio impedances must match, so whoever you talk to for advice must know your radio impedance in order to assist you.

Lengthening the antenna cable

When lengthening the cable, buy the best coax with the lowest loss that you can afford. Getting enough to make a single run from the radio to the antenna will avoid the inevitable signal loss and possible corrosion inherent in a splice or connectors. Adding connectors can cause up to 2.5 dB (decibel) loss per connector. In some cases splicing the cable with connectors is unavoidable, such as a break in the coax on a sailboat with a mast that must be removed periodically.

If, during installation you find that you need to penetrate a bulkhead, drill the hole through the bulkhead, then install a bulkhead liner, a rubber grommet or foam to prevent chafing of the cable.

Sharp bends in the coax should be avoided when installing the antenna cable. Also, avoid pinching the coax in the clamps or ties when securing the cable in place. Kinking, twisting, pinching or stretching the coax cable will cause its impedance to change, interfering with transmission.

Connectors

In most cases, the antenna manufacturer has already connected the coax permanently to the antenna radiators, leaving only the connection to the radio to be made on site. Many sailboat whips, however, leave the connection of the coax to the antenna to the installer. These critical connections are the ones where the installer must apply a connector to the coaxial cable.

Most connectors supplied by the manufacturer will be type PL-259, (see "how to" video below) but there are many grades of connectors. If for antenna doesnt include the connectors, or you suspect that the PL-259 connectors supplied with your antenna are of low quality, consider using a higher quality PL-259 that's either gold-plated, or has a gold-plated pin. These connectors inhibit corrosion and provide a superior radio signal. Wrap and seal the joint between the connector and the coaxial cable to insure against moisture intrusion which will corrode the copper braid in the coax. You can spray a silicon protectant or force a heat shrink compound into the joint, and then cover the connection with a marine grade heat shrink tubing or a quality self-amalgamating tape.

How to Install a PL259 Antenna Connector

Splicing coaxial cable by soldering the core and braid is not recommended because it will change the impedance of the cable. But if you must solder, you'll find the technique is not terribly difficult to master but requires patience, the correct solder and soldering iron. Use a 30-watt minimum soldering iron and a 60/40 resin core solder. If you don’t have patience, or experience wielding a soldering iron, and don’t feel comfortable doing this particular part of the installation, find a friend that does have experience or hire a pro. A bad connection will result in signal losses and impedance.

In addition, using twist-on cable joiners is not recommended for extending a coax cable. To add a length of cable, the best way is with a high quality connectors—a barrel connector (PL-258) on the end of one cable and a PL-259 on the other will connect the two cables together.

Again, rather than lengthen a cable by soldering or with connectors, it is always the best practice to replace the entire cable with a new one of the correct length in one piece if at all possible.

...and Testing

After making any connection, test both the connection and the antenna. Tune your radio to a weather channel and disconnect the antenna completely. Your signal should either disappear or be very weak. Reinsert the pin portion of the connector ,center conductor, into the radio without making contact with the outside ground ring. You should now hear a signal but with no fidelity or strength. Push the connector all the way into the radio and you should hear a normal signal. If not, use your ohmmeter to test for a short circuit.

Mounting

The material of the mount should match the material of the antenna’s ferrule if at all possible, a stainless steel or brass mount with a stainless threaded portion on the antenna or plastic on plastic. Some stainless steel whips for mast mounting thread the bottom coil of the whip through an angle bracket.


Several types of rail mounts are available for use on a sternrail, handrail or pole made of tubular metal. Long antennas, especially on powerboats that must pass under low bridges, should use pivoting mounts so that the antenna can be easily lowered and raised.

If the antenna mount is to be fastened to a fiberglass portion of a deck or superstructure of the boat, the antenna base should be through-bolted with a metal or wood backing plate for reinforcement. Antennas with extensions, or those over eight feet, generally require a standoff bracket mounted four or five feet from the base to provide additional bracing for the antenna and to dampen its motion.


Use the base of the mount and bracket as a template for drilling holes. Don’t forget to use ample bedding compound when fastening to prevent leaks into the boat. If the cable must pass through the deck or other structure of the boat, use a watertight cable gland sized to fit your coaxial cable.

To buy a VHF/SSB Antennas

SSB and HAM Antennas

As with VHF antennas, the mounting style, materials, coaxial cable, and connectors all need to be matched with the use and type of boat you have.

If you going far offshore, out of contact via VHF radio, often want the advantages of a communication system with longer range. For this type of work, they usually turn to high frequency (HF) radio communications, which falls under the umbrella of marine single side-band (SSB) or HAM. This type of communication spans the frequency spectrum from medium frequency to ultra-high frequency depending on limitations of the user's license. Since HF radio bands use skip propagation rather than line-of-sight, it is capable of worldwide communications.

When creating a good high frequency antenna system, sailboats have the advantage in that the backstay can be used as a long wire antenna with the proper cable insulators. Powerboats need to rely on antenna whips for SSB or HAM communication and in both cases the length of the antenna will determine the usable frequency range.

Below is the first and only completely insulated SSB marine antenna by Imtra.

A good midrange antenna when used with a tuner will be 23-24' in length for the 2-30MHz (12-80m) range. This should serve all SSB users and HAM operators well. Look for a minimum of 250 watts and maximum of 1,000 watts of input power.

VHF Antennas

When shopping for a VHF antenna, there are four important considerations:

Do you own a powerboat, a trawler with a mast or a sailboat? Where do you most often use your boat or what is the size of your boat?

Where and how will the antenna be mounted?

Because powerboats are considered relatively stable platforms but are low on the water which reduces line-of-sight transmission distance, an antenna with a higher gain can be used without loss of transmission signal. If you own a sailboat or trawler with mast, a lower gain, shorter antenna can be mounted on the top of the mast giving you longer line-of-sight range, and when the boat is on a heel, you won't lose the signal into the water.

A small powerboat with a nine dB, 23' antenna may look a little strange, but on a larger motor cruiser with a flybridge or third deck, 23 feet may not be so bad. If your boating extends no further than the ICW or a small inland waterway and you're never out in the ocean, then perhaps a 3', low-gain antenna is all you need. However, if you fish out of sight of land, then perhaps the longer antenna with higher gain is right for you.

The mounting location needs to be determined since antennas can be purchased with either a bottom (end) or side cable feed, and you'll want to purchase your bracket at the same time.

Other considerations will be the frequency range of the antenna and the type of coaxial cable, its length, and the connector. The frequency range should be between 156 and 164 MHz. Most manufacturers supply a fixed length of coaxial cable and a connector with the antenna. The 6" (1dB) vertical VHF Antenna by Imtra Company (on photo below) come with Cable, includes 18m coaxial cable plus "PL259" male connector.

To see all range of Imtra's VHF Antennas visit: /imtra.com/antennas-glomex-antennas-vhf.htm/

Be sure the cable is listed as RG58, RG58C/U, RG8 or RG8X, the last of which is UV-stabilized, low-loss cable. Don't use foam-filled RG8U cable because it will collect moisture and eventually corrode the cable, creating impedance. Coax should never be cut and spliced if possible as impedances, or line loss, will occur.

Match the cable to the connector. For RG58 or RG8 cable and their variables, the most commonly provided connector is the PL259 which requires an adapter to fit these smaller diameter cables. Some antennas come with an SO239 connector on the end to connect the PL259 fitting to the antenna.

The antenna ferrule and mounting materials should be matched to the type of boating you do. Use metal materials if the antenna will be subjected to flex in rough seas. If you use your boat only on calm days, the plastic mount will suffice.

One other item your antenna should have is a built-in DC ground which reduces static buildup on the isotropic radiator (element) and static noise on the receiver.

Some manufacturers now make combination "VHF" and "mobile phone antennas".

Mobile phone antennas should serve the 800-900 MHz frequency range with no more than 50 ohms of impedance. If your cell phone operates in both digital PCS and analog modes you'll want a dual band antenna operating in both the 800-900 MHz and 1800-1900 MHz frequency ranges.

A longer, higher gain antenna will provide longer range communication when mounted as high as possible on a stable platform. Most marine mobile phone antennas are available in 3.5, 6 or 9 dB gain, ranging in length from 2-8'. Check the manufacturer's SWR rating for the frequency range usage, looking for a 1.5:1 or less. The cable supplied needs to be RG8, RG8X or RG213 and the connector an "N" or "TNC" type. An adaptor may be required to fit your model of (GSM, Smartphone) mobile phone. The antenna you choose should have a built-in DC ground.

The Mobile Phone Antennas have become so much a part of our lives that we're taking them with us out on the water. Unfortunately, unless you're boating in a heavily populated area and remain close to shore, the short antenna on your cellular phone won't be enough.

If you carry a mobile phone on your boat, these might be worth checking out. These combination antennas are 8 feet long with a 6dB gain.


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