Features July 15, 2000 Issue

GAM SS-2 Top Short VHF Antenna

Among 8' 6db models, the Shakespeare 5225XT performed perfectly. Others that rated well include the Shakespeare 5399, Digital 528-VW and the Antenex 4-footer.

The best VHF radio won’t work without a quality, properly installed antenna. But many boat owners don’t put much effort into choosing one.

Our test group of VHF antennas from seven
manufacturers had eight 8-footers; two
4-1/2-footers; two 4-footers; two 3-footers;
one 16-footer and one at 9-1/2 feet.

The antenna and its cable are the weakest links in your ability to communicate via VHF. Most radio problem complaints are, in fact, due to a defective antenna, damaged cable or an improperly installed connector.

The Market Players
We selected 16 antennas from seven manufacturers. Since our last report (July 15, 1996), Glassmaster has exited the marine antenna market. Glomex, an Italian company, and Antenex, an American manufacturer of commercial land mobile antennas, have entered. We also tested an antenna marketed under West Marine’s Sea Ranger brand. Shakespeare continues to be the largest manufacturer.

The Right Antenna
Normally, radio waves are radiated from an antenna equally in all directions, including straight up into the sky, where they are not effective. But antennas can be designed to eliminate vertical radiation, focused outward and parallel to the water, amplifying the signals in the desired direction. Received signals coming from the same direction also increase in this fashion. This phenomenon is referred to as the antenna’s gain. Antenna gain is measured in decibels (dB) over a fixed reference value. The dB is a logarithmic function; for each 3 dB of gain, the signal is effectively doubled. The total signal produced by your gain antenna is referred to as effective radiated power (ERP). Assuming absolutely no cable loss (which is impossible), a 25-watt VHF radio would produce an ERP of 50 watts with a 3 dB gain antenna and an ERP of 100 watts with a 6 dB gain model.

The disadvantage of increased gain is a decrease in the antenna’s beam width. When mounted near water level, this is generally irrelevant. High above the water, however, this narrower beam can result in signal fading as your boat rocks or heels, often referred to as the “searchlight” effect.

Increased gain, however, does not necessarily increase communications range. Range is limited by the laws of physics. VHF radio waves have a finite “radio horizon,” as does radar. This horizon is slightly farther than the visible horizon. No matter how much gain or how powerful your radio, you will not be able to exceed this distance without the presence of some form of unusual atmospheric phenomenon, which can greatly extend VHF communications.

Installing a higher gain antenna will increase the reliability of your communication within the constraints of VHF communications range. Your signal will be stronger, clearer and fade less, and so will the received signals.

Antenna height, however, can dramatically increase range, just as a person’s visibility increases if he or she stands on a mountain.

Most sailboats have a 3' 3db VHF antenna mounted at the masthead because its wider beam compensates for heeling, but an 8' 6 db on deck is a good backup, and less vulnerable to damage from lightning.

The Right Cable
The cable is just as important as the antenna. Most of the antennas we tested came supplied with RG58A/U cable, which is adequate for short runs but produces a great deal of communication loss over longer distances. RG8X cable was supplied with some antennas. This slightly larger—and more durable—cable has approximately 1.75 times less loss per foot than RG58 cable. It should be used for anything over a 25' cable run. Even larger cables, such as RG213, RG8 and Belden 9913, should be used in the largest boats where routing space is available and the antenna is a considerable distance from the radio.

How We Tested
To measure antenna performance, we devised a simple yet quantitative test. The antennas were taken several hundred yards away from the receiver site and alternately connected to the same radio. At the receiver site, we used a digital radio frequency field strength meter to measure how much energy each antenna radiated.

The meter records the actual received amount of radio signal, which is taken in dBm (dB per square meter), a standard unit of radio field strength. A more efficient and higher-gain antenna will beam more signal to the receiver antenna. Conversely, a poorer antenna will lose signals internally or fail to produce gain and result in a lower reading at the receiver site. All testing was done with our radio set on its low-power mode (1 watt).

For this power level and at the test distance used, readings ranged between -22 and -30 dBm. The higher readings, or lower negative readings, indicate the stronger field strength. For example, -32.5 dBm is a much weaker signal than -23 dBm.

In addition, the efficiency of the antenna was further evaluated by attaching a directional watt meter between it and the radio. This meter measured the power going to the antenna from the radio and any power reflected back and essentially not transmitted. This reflected power is a result of a poorly tuned or constructed antenna. The ratio of forward to reflected power is called the voltage standing wave ratio (VSWR or SWR).

A ratio of 1:1 indicates that all of the transmitted signal exits the antenna and that none is reflected back. A VSWR of less than 1.5:1 is considered acceptable for a marine VHF antenna. In our tests, we encountered VSWRs of 1.6:1 and 2.0:1 in some models. The antennas were checked on channels 1, 16 and 88. Doing this allowed us to determine the antennas’ bandwidths. A marine VHF antenna should be designed to operate equally well across the entire list of usable frequencies. Therefore, there should be little or no difference in VSWR between the lower and higher channels.

In addition, we connected each antenna to our IFR Com-120B communications analyzer through a return loss bridge. Using the analyzer’s tracking generator and spectrum analyzer, we were able to precisely determine the optimum operating frequency or center frequency for which each antenna was manufactured.

Shakespeare
The largest and most popular manufacturer of marine antennas is Shakespeare, which produces numerous models that fit every possible application. It also sells a full line of mounting accessories. The quality is generally good. However, lower-end models of lesser quality should be avoided because of questionable durability.

The cable used with all models was adequate, but not the best available. Some antennas rattled, indicating that their internal elements were not mechanically attached to the antenna casing. At the least, this can be annoying if the antenna is located within earshot. At worst, the repeated banging together of the antenna parts will shorten its life.

Shakespeare’s selection of antennas has always been confusing. Many models are very similar, if not identical. Most suppliers stock a cross-section of models. Shakespeare’s Galaxy line consists of its premium-grade models, including the 5400XT, 5225XT, 5399 and 5225FLT models tested. Versions of its standard series of antennas that we tested include the 5202, 5206C and 5102.

Interestingly, Shakespeare’s antennas did not perform consistently, with wide variations between models.

The Galaxy 5400XT performed very poorly. It exhibited a lower-than-expected radiated signal strength and very poor VSWR on all frequencies. This 5400XT was a prototype and may have tested poorly due to this fact, said Don Henry, director of the Shakespeare marine products group. Conversely, the Galaxy 5225XT tested perfectly and is our top pick for 8' antennas.

The Model 5202 antenna ($90) tested adequately, but you can get the top-rated 5225XT for only $10 more. The 5206C was the least expensive Shakespeare tested and performed exceptionally well. This model is a great low-budget antenna, but because it is hollow and rattles, we are concerned about its durability.

The 5102 is again a poor choice based on price versus performance. The Galaxy 5399 (9.5') is an excellent high-gain antenna. It performed very well and is very well constructed. We highly recommend it for applications where a larger antenna is desirable.

The Shakespeare 5225FLT contains so-called “Breakthrough Antenna Technology” that filters radio interference from commercial transmitters on adjacent channels, such as those operated by paging companies. For sailors in and around large cities, this interference can be a major annoyance, making it almost impossible to tolerate listening to your VHF radio. It is usually more prevalent with low-cost, poorly designed radios but also may occur with better radios.

Shakespeare has tried to minimize these signals inside the antenna. We were unable to directly test this feature but did note that the 5225FLT produced a very sharp drop in efficiency outside of the marine frequency band. This would certainly help to decrease the effects of this interference when it is used with a quality radio.

Otherwise, the 5225FLT performed well but showed a higher VSWR than the standard model 5225XT antenna. If you routinely experience the type of interference discussed above, the 5225FLT would by a good choice.

Bottom Line: As expected, most of Shakespeare’s antennas tested very well. However, the growing inconsistency of performance among similar Shakespeare models is a concern.

GAM Electronics
The Gam SS-2 stainless steel whip antenna is very well-made and performed exceptionally well during testing. Radiated signal strength was within our expected range and SWR was perfect on all test channels.

Gam’s model TG-3-SH(L) antenna also performed very well. This model, an adaptation of an antenna used mostly for commercial boats, mounts directly onto a 1.25" pipe. The installation is favored by commercial boat owners because it is very durable, said Gam president Ed Russell. Recreational boat owners can use this model, but only with an adapter ($25).

Bottom Line: The Gam SS-2 is a very good antenna at a fair price, our top pick among the small antennas tested.The TG-3-SH(L) model we rated as Good.

Digital Antenna
Since our first look at its products, Digital Antenna has begun offering a 2-year warranty and now includes a customer service phone number with its products. Digital Antenna also manufactures marine cellular and SSB antennas.

We think its antennas are constructed well and we especially like the pre-attached miniature connector, which eliminates the need to field-install a connector to the antenna’s cable. The possibility of a poorly installed connector ruining your ability to use your VHF is also negated. Unfortunately, it also limits the distance your antenna can be installed from the radio.

The Digital 528-VW is a very well-built, compact 4.5' VHF antenna. It performed well; we consider it a very good choice for the masthead or a small boat where mounting an 8' antenna on deck would be ill-advised.

Digital’s 532-VW is a large and expensive 16' antenna designed for bigger boats. It is rated at 10 dB gain. However, it performed very poorly. In fact, it produced the worst measured signal strength when compared to several other antennas at several measurement ranges.

Other notes: “Digital” is only a catchword to entice sales. VHF radio is still an analog technology and will remain so for some time. Even Digital Selective Calling uses analog modulation to send information.

Digital Antenna’s claim that its models “Transmit Farther Than Any Other Antenna” should be taken with a grain of salt.

Bottom Line: The Digital 528-VW is a good antenna, and we recommend it for applications that require a smaller fiberglass antenna. On the other hand, Digital’s 532-VW, as tested, is a poor choice for any application, in our opinion.

Metz
Metz’s VHF masthead antenna, promoted as a replacement for larger VHF antennas, is its only entry in the marine VHF market. Despite Metz’s reputation for quality, this model tested less than admirably. Its VSWR measured high but within acceptable levels. Signal strength was below that of other similar models.

Bottom Line: Low performance makes this model hard to recommend.

Glomex
Glomex Marine Antennas, Inc., the latest newcomer to the market, is an Italian company that began selling its products in the US several years ago. In addition to VHF antennas, the company offers a full line of mounting hardware, marine television antennas, cellular antennas and other related items. All products include a limited lifetime warranty.

The two Glomex antennas tested are well-made. The RA106 model is packaged with all necessary hardware, connectors and 60' of antenna cable. This antenna was disappointing, however. Measured signal strength was 2 dB below that of competitive antennas; VSWR was on the high side but still acceptable. We also question the inclusion of RG-58 cable. At these lengths, a thicker and lower-loss RG-8X cable would be a better choice.

The Glomex RA1225, a fiberglass 8' antenna, is also supplied with RG-58 cable. It tested well but still exhibited VSWR levels higher than we would have preferred. Glomex prides itself in including solderless, twist-on connectors with its antennas. We seriously question the ability of these to survive long term in a saltwater environment. This approach cannot guarantee a proper and reliable connection between the cable antenna and radio, in our opinion.

The cable supplied with the RA106 model was of adequate quality, but we have seen better. With the RA1225, we found cable with a very light braided shield instead of an aluminum foil shield. We would much prefer to see a higher-quality conventional coaxial cable.

Bottom Line: We cannot get very enthusiastic about Glomex antennas due to concerns about their cable, solderless twist-on connectors and average test scores.

Antenex
Antenex is a large U.S. manufacturer of commercial land mobile antennas. Its products are widely used by industrial, commercial and public safety two-way radio users. The MAV1602 model is well-made and realistically rated for 2.5 dB of gain. The MAV1602 performed very well. However, it did exhibit higher-than-expected VSWR on channel 88. This is also the only antenna designed around the radio industry standard NMO-type mobile antenna mount. This arrangement makes it easy to install on thin metal surfaces should this be necessary.

Bottom Line: We recommend the Antenex MAV1602 for masthead mounts on sailboats and for on-deck installation on small boats.

Sea Ranger
The 8' Sea Ranger 2006-N fiberglass antenna from West Marine performed very well but is of a noticeably low-end construction. Its mounting ferrule is plastic and it is very lightly built.

Bottom Line: Despite its performance, the Sea Ranger simply does not appear built well enough to last a long time.

Among 8' fiberglass antennas, the Shakespeare 5225XT and the Shakespeare 5399 rate best. Between the two,our top choice is the lower-priced 5225XT. Our Best Buy is the $37 Shakespeare 5206C.

The 3' Gam SS-2 remains our pick among the smaller antennas tested, followed by the Digital 528-VW (4.5'), which costs more than twice as much, but its lower dB is better suited to masthead mount. The2.5 dB Antenex 4-footer is also a good choice.

 

Also With This Article
Click here to view the VHF antenna specifications.

 

Contacts- Antenex, 2000-205 Bloomingdale Rd., Glendale Heights, IL 60139; 800/323-3757; fax: 630/351-9009; www.antenex.com. Digital, 1551 NW 65th Ave., Fort Lauderdale, FL 33313; 954/581-7007; www.digitalantenna.com. GAM Electronics, 191 Varney St., Manchester, NH 03102; 603/627-1010; fax: 603/622-4738; www.gamelectronicsinc.com. Glomex, 1747 Independence Blvd., Suite E 12, Sarasota, FL 34234; 941/355-3381; www.glomex-marine-antennas.com. Metz, 2 Lily Pond Rd., Gilford, NH 03246; 603/528-2590. Shakespeare, Box 733, Newberry, SC 29108; 803/276-5504; www.Shakespeare-ce.com. Sea Ranger, West Marine, P.O. Box 50070 Watsonville, CA 95077; 800/262-8464; .

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