An integral part of any VHF installation effort is finding first the right VHF antenna to use. Knowing how to identify the right antenna to use, and how exactly they work will put you in a more advantageous position because it will significantly help you in facilitating better communication lines with shore stations and other boaters.
The role of a VHF type of antenna is to furnish a radiator functionality for the power which the radio transmitter is producing. On top of that, it also ensures that this energy will be radiated in the right direction.
It is also important to secure and protect antennas inside a weather-proof enclosure, this can be made from a corrosion-resistant metal. Plastic will also work, though. In addition, this enclosure should be sturdy enough to withstand any kind of substantial force that a boat pounding against heavy, turbulent heavy seas could generate.
Gains and Losses
People are so inquisitive to know if they need to match the loss brought about by the coaxial cable of the antenna to the antenna gain in dB. While these concepts paint us a picture that they are somehow associated with each other, there is no way you should be trading one for the other. Here is the underlying reason for that:
A 3dB gain increase is tantamount to signal strength doubling: 6dB is to be seen as a fourfold spike and a 9dB is seen as an eightfold spike. Transmission is not bound to undergo any kind of change, what happens instead is that it becomes concentrated.
It works pretty much the same as how we can make an adjustable flashlight concentrated, from something wide and diffused to one that is narrow and bright. Therefore, if you happen to have a 6dB antenna, it will make it sound like it comes with a larger transmitter compared to a similar radio that comes with a 3dB antenna.
While coaxial cables are indeed very efficient, they have this inherent tendency to lose energy with every foot. A small RG-58U coax tends to lose a minimum of 3dB, which is for every 49’ of a run.
We reckon that this will be like when you happen to have a 49’ run of cable, it will make your radio sound like that it is transmitting from a 12.5 watts instead of 25.
Running the same cable 98’ will make you sound like you are on a 6-watt radio. Bear in mind that when you put your antenna on an 80’ mast, even when you are using a small type of coax for this, you are still likely going to get a good range. However, the coax will have your effective power reduced.
This renders us to be more prudent and make use of any available large coax, especially on long runs. This paves the way for a trade-off here, and one of those is more weight aloft. This will induce heel to increase and weaken sailing performance. Therefore, you will need to compromise.
VHF antennas are usually made of fiberglass or stainless steel. A short 3dB stainless steel “whip” antenna will likely produce lesser amounts of windage with an appropriation of a wide radiation pattern, which a heeling sailboat necessitates.
Small powerboats are also known to utilize stainless whip antennas, the reason being that they are rugged. As for the fiberglass tube antennas, these types tend to vary in their quality.
If you are looking for a highly durable type of antenna, we recommend that you look for ones that have a smooth polyurethane. They usually last for about 5 years to a decade. This type of antenna makes use of stainless steel ferrules to make the product offering more durable.
They combine this with brass or copper, or both, for maximum efficiency. Nylon ferrules are used by rather less expensive antennas. But they are deemed as inferior quality since they are not as strong as the stainless-steel type or chromed-brass that are normally used by top-of-the-line VHF antennas.