vhf antenae

[mellowyellow]

just got my new VHF along with a VHF/am-fm splitter and a 36" antenae. what is a conservative<br />VHF range? does radio create any interference?<br />(lakes erie and ontario region)<br />as always, thanks in advance.<br />M.Y.

 

[mellowyellow]

Re: vhf antenae

where's spellcheck?

 

[Capt. Bob]

Re: vhf antenae

Hi mellow,<br />All fixed-mount VHFs have a maximum output of 25 watts, the maximum allowed by the FCC. VHF (very high frequency) is a line-of-sight system, which means the radio waves won't bend to follow the curvature of the earth. The VHF antenna must "see" the antenna of a distant station. Therefore, antenna height is more important in determining range than radio wattage. The effective useful range of a VHF radio is 20-25 miles. That includes yours with a 36" antenna. The higher the antenna, the more range. A large ship may be able to communicate at 60 nm. We are talking about communicating with a land based position and a tower antenna. Two boats with limited antenna height will not be able to to communicate 20-25 miles.<br />Handhelds have a maximum output of six watts. Due to their short antennas, they have a limited range of five miles. <br /><br />Hope this helps,

 

[mellowyellow]

Re: vhf antenae

thanks as usual Capt. Bob <br />need to know my "limitations" as lake's erie<br />and ontario are pretty big and can get a little<br />scary at times. 25mi. is more than I'll ever need<br />I think in a 16' boat. I'm not that crazy (anymore)

 

[SeaHorse]

Re: vhf antenae

Your range will be limited by (1) the gain of your antenna in db; and (2) the curvature of the earth. Your 36" antenna is probably rated at 3 db whereas the 8 footer will be rated at 6 (twice a good). <br />Use this formula for calculating the curvature range:<br />square root and antenna height (in feet) times 1.42 equals range in miles of YOUR antenna. Then add the range of the receiver's antenna to yours. So, your antenna is probably mounted 3 feet off the water plus the 3 foot antenna length equals 6 feet. Square root of 6 times 1.42 equals 3.5 miles. If you're talking to a similar boat (same antenna height) you add another 3.5 miles giving 7 miles total. If you both had 8 foot antennas the total would be 9.5 miles. Of course the Coast Guard station will have a very high antenna so you'll be able to get them maybe twice as far. <br />Don't count on contacting another boat 26 miles away.