VHF ariel
- Thread starter canman
- Start date
Kev1n
Well-known member
Arthur, I’d just buy another glass fibre aerial about four foot long and with high gain.
The aerial’s range works on line-of-sight, so the higher up it is the longer the range. The difference between a four foot and eight foot is pretty minimal but it’s still worth mounting it high up on the cabin roof. Make sure it comes with the right connector for your radio.
The aerial’s range works on line-of-sight, so the higher up it is the longer the range. The difference between a four foot and eight foot is pretty minimal but it’s still worth mounting it high up on the cabin roof. Make sure it comes with the right connector for your radio.
mark
Well-known member
its a complex area! a 4 foot antenna will resonate at half the wavelength, an 8 foot will resonate at full wavelength at channel 16 frequencies. the way an antenna resonate affects range a lot. as you move to different channels the frequency and therefore wavelength changes - the percentage difference between the antenna's fixed resonant frequency and the frequency you are transmitting on will also be a lot greater with a half wave versus a full wave as you move away from channel 16 (antennas are optimised for use on 16), the gain characteristics are usually higher with a longer one as well
personally I'd always go for 8' If practical
not the best diagram but quicker than drawing one myself!
range is estimated at
approx 1.42 multiplied by square root of antenna height at the top
the extra 4 foot can make an important difference. Most important thing of all is get it as high as possible, keep it as straight as possible, none of this raked backwards looks good malarkely - if it ain't straight you'll be transmitting upwards - look at the lifeboats - they rake theirs forwards so when the boat is planing, the antenna sites perfectly vertical. keep the cable length to a bare minimum. a lot of them come with 30' of cable - cut off what you don't need as you can lose a lot in the coax
personally I'd always go for 8' If practical
not the best diagram but quicker than drawing one myself!
range is estimated at
approx 1.42 multiplied by square root of antenna height at the top
the extra 4 foot can make an important difference. Most important thing of all is get it as high as possible, keep it as straight as possible, none of this raked backwards looks good malarkely - if it ain't straight you'll be transmitting upwards - look at the lifeboats - they rake theirs forwards so when the boat is planing, the antenna sites perfectly vertical. keep the cable length to a bare minimum. a lot of them come with 30' of cable - cut off what you don't need as you can lose a lot in the coax
Metz marine VHF radio/ AIS antenna (aerial): Lifetime warranty. | eBay
Was looking at these on Ebay, thought they looked the buisness. Anyone got any thoughts!
Thanks for your thoughts Mark & Kevin, didn't realise it was such a complex thing to get right.
Was looking at these on Ebay, thought they looked the buisness. Anyone got any thoughts!
Thanks for your thoughts Mark & Kevin, didn't realise it was such a complex thing to get right.
