Have a question about VHF Antennas? Check out these FAQ's!!!
If you have a question regarding VHF Antennas E-mail us at: contact@bestoutdoorselectronics.com . We enjoy answering these questions so don't hesitate to ask!!!
What should be the main reason to buy your antenna?
Is it true that the higher the antenna, the further the transmission and the better the reception?
Does the gain of the antenna really matter?
What is the minimum distance that I can mount the antenna from the radio?
How do power losses occur in an antenna?
What is gain in an antenna?
How does the ground system affect an antenna?
What makes an antenna reach a greater distance?
Can I cut the cable on my VHF antenna?
How can I check the VHF antenna to make sure it is working?
How do you install the PL-259 connector?
Will metal or other objects that are close to the antenna affect it?
Do I need a ground plane for a VHF antenna?
What is the antenna's wavelength?
How high must the antenna be?
What range can I expect from the antenna?
What is the receiving zone for my antenna?
What should be the main reason to buy your antenna?
The antenna is part of your life support system during an emergency. Reliability should be the main decision factor in purchasing our antenna. The radio and antenna act as one system that must perform in all weather conditions and at maximum range. Simply put, having a good radio with a poor antenna does not give you the best odds when you are in a distress situation. It is our belief that Digital Antenna has the best and most reliable product on the market -- one that beats the competition in both gain and distance, resulting in an increased safety margin.
Click here for top of page
Is it true that the higher the antenna, the further the transmission and the better the reception?
Yes, in general, that can be one of the factors influencing performance. However, for most uses, mounting the antenna in the usual locations is acceptable.
Click here for top of page
Does the gain of the antenna really matter?
Yes, it does. The gain of an antenna translates to greater distance for transmission and reception. A gain of 6db usually results in a performance increase of four times the radio's power output and eight times with a 9dB gain. However, other factors can be equally important, including the tuned frequency of the antenna and its SWR. Digital Antenna tunes all of its products in accordance with the median frequency of usage, (i.e., VHF will be tuned for 156.8 Mhz). Our SWR ratio approaches 1:1, reducing most of the losses associated with our competitors' antennas. All of these factors are important when it comes to choosing an antenna.
Click here for top of page
What is the minimum distance that I can mount the antenna from the radio?
In order for no squealing to occur from transmission interference, you must mount the antenna no less than three feet away. Of course, the greater the power of the radio, the greater the minimum distance.
Click here for top of page
How do power losses occur in an antenna?
The gain of an antenna is closely related to its directivity. Because directivity is based solely on the shape of the radiation pattern lobes, it does not take into account power losses that may occur in the actual antenna system.
Every Digital Antenna marine antenna is tuned for minimum standing wave ratio (SWR) which approaches 1:1, reducing the system loss significantly. Additionally, a ferrite choke bead is used to contain RF power in the antenna system. By using a choke bead, all RF power is directed into the radiating element and prevented from leaking back to the transmission cable.
This technique increases usable RF power and minimizes cable interference with other electronic equipment. Also, Digital Antenna uses its exclusive marine grade low loss UV stable RG8X cable to reduce transmission line loss in all Digital Antenna marine antennas.
Click here for top of page
What is gain in an antenna?
Gain in an antenna is not the creation of power, but rather a simple refocusing of energy from all directions to a specific direction. Gain is measured in decibels (dB). Ideal vertical plane radiation pattern showing the difference in antenna radiator element lengths.Vertical antennas are in fact quite directional, except in the horizontal or azimuth plane.
The quarter wavelength antenna has the highest angle of radiation; however, it also has the lowest gain. The 5/8 wavelength antenna has both the lowest angle of radiation and the highest gain, which gives superior performance at sea level.
Click here for top of page
How does the ground system affect an antenna?
The vertical antenna works well only when placed over a good ground system. The success or failure of an antenna system depends on whether or not it has a good RF ground. Poor grounds cause antennas to operate at less than best efficiency. In fact, it is possible to lose between 50 and 90 percent of the RF power by heating the space under the radiation lobe, instead of transmitting into the air.
Click here for top of page
What makes an antenna reach a greater distance?
The advanced ground system internal to all Digital Antenna marine antennas allows 4.5dB through 10dB gain antennas to have a greater range in any sea conditions.
Note that by increasing the ground system efficiency, useful RF power is actually directed closer to the water surface where it is needed. Most well designed 5/8 wavelength 6dB antennas will transmit the same distance in the sky; however, the ground efficiency determines the actual communication range at sea level.
Click here for top of page
Can I cut the cable on my VHF antenna?
Yes, if you need to. However, you should leave at least three feet of coax, measured from where the cable exits the antenna.
Note: This is NOT true for all antennas. CB antennas' coax generally should NOT be cut.
Reasonable lengths of excess cable can be rolled in a coil of at least 8 inch diameter and stowed in an out-of-the-way place.
Click here for top of page
How can I check the VHF antenna to make sure it is working?
You should transmit to a friend's receiver from a range of known distances, and have the friend assess your transmission for quality. Note that the US Coast Guard frowns on radio test calls made to them.
To help you measure the efficiency of your antenna/radio system more scientifically, Shakespeare makes two antenna / radio testers - the ART-2 and ART-3.
The ART-2 will test the output power of your transceiver, as well as the antenna's VSWR of the antenna.
The ART-3 tests transceiver output power, antenna VSWR, and proper receiver sensitivity.
Click here for top of page
How do you install the PL-259 connector?
An instruction sheet for installing the PL-259 connector is included with the antenna. Follow the instructions and consult the diagrams.
For true ease of installation without soldering, check out Shakespeare's innovative Centerpin® solderless connectors. The PL-259-CP and PL-258-CP connectors are gold-plated brass construction.
Click here for top of page
Will metal or other objects that are close to the antenna affect it?
Yes they will. It is best to locate the antenna at least three feet from any metal objects or other antennas.
Click here for top of page
Do I need a ground plane for a VHF antenna?
Not necessarily, Shakespeare VHF and CB Marine Band antennas are designed with independent ground planes built in.
SSB antennas, on the other hand, must be properly grounded.
Click here for top of page
What is the antenna's wavelength?
It can range from 1/4 wave to 5/8 wave, depending on the length and style of antenna. Please see the antenna manufacturer’s specifications section for information on your particular antenna.
Click here for top of page
How high must the antenna be?
There is no particular height requirement. However, remember that the higher the antenna, the better the reception.
Satellite Radio antennas only need a clear view of the Southern sky - for them, height is not as important.
Click here for top of page
What range can I expect from the antenna?
To determine the range of an antenna, multiply the square root of its height (In feet) above water by 1.42. This gives the range in miles.
Remember to perform the calculation for BOTH vessels, then add the results to get the range between two vessels.
Click here for top of page
What is the receiving zone for my antenna?
On all Shakespeare VHF Marine antennas the receiving zone is 360 degrees - or omni-directional.
Click here for top of page
