Two things to keep in mind. First, VHF is line-of-sight; the radio waves don't follow the curvature of the earth. Your antenna must "see" the other antenna. This means, the higher the antenna, the greater the range. Generally speaking, the top of a mounted whip antenna for a fixed unit will be higher than the top of an antenna for a handheld. I think some handhelds have connectors to attach to an external antenna, but I don't know for sure.
Second, there's a significant performance difference: The maximum power output of a handheld is 6 watts. Maximum output of a stationary mount unit is 25 watts. Power and antenna height translate directly to range. Most handhelds aren't dependable for more than about 5 miles. Being that VHF is line-of-sight, the power issue is not such a big deal because you'll frequently lose contact because the other station goes over the horizon rather than losing the signal due to insufficient power. However, more power when the stations are just at the margin of losing contact due to going out of line of sight can make the difference between understanding and not understanding a message. The formula for determining range is: (Square root of height of antenna above the water) x 1.42 = range in miles. So if you're standing at your lower helm with a handheld, and the height of the antenna is 9 feet above the water, the range would be SQRT(9) x 1.42 3 x 1.42 = 4.26 miles. If you have an 8-foot antenna (most 6 dB antennas), mounted on a flybridge rail 15 feet above the water, the antenna height would be 23 feet, so the range would be SQRT(23) x 1.42 4.795 x 1.42 =6.81 miles -- almost a 40% improvement in range. If you have a 20-foot fixed antenna (most 9 dB antennas are between 18 and 23 feet) mounted on a rail 15 feet above the water (35 foot antenna height), range would be SQRT (35) x 1.42 5.91 x 1.42 =8.4 miles - double the range of the handheld. That's why I'd buy a handheld for use in the dinghy or in harbor, or with someone you know to be close, or if you have to ditch; but I'd always want to have a fixed mount unit with a good whip antenna, with a 9 dB gain and a 5/8 standing wave ratio (SWR) antenna. If I hit a log and start taking on water, I want my Mayday signal to blast the Coast Guard radio operator and everyone else around out of their seats. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "UnifliteWorld" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/UnifliteWorld?hl=en -~----------~----~----~----~------~----~------~--~---
