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Old 08-12-2019, 18:17   #1
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AIS VHF/UHF Antenna

I was about to pull the trigger on a $100+ 1.8m traditional style marine antenna when this $25 VHF/UHF one popped up claiming to be suitable for AIS as well.

Quote:
Compatible with Marine Boat AIS VHF Radio, Two Way Radio
Frequency Range: VHF 136-174MHz, UHF 400-470MHz


But will it really work?
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Old 08-12-2019, 18:26   #2
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Re: AIS VHF/UHF Antenna

It might, but personally I would not risk it. The whole point of AIS is to be seen by other boats (at least thatís what I want) and an antenna that short will surely have pretty poor gain.
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Old 08-12-2019, 18:32   #3
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Re: AIS VHF/UHF Antenna

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Originally Posted by GILow View Post
It might, but personally I would not risk it. The whole point of AIS is to be seen by other boats (at least thatís what I want) and an antenna that short will surely have pretty poor gain.
Gain was the one thing not mentioned in the ad.
All other brand name antennas I looked at did.
I guess $100+ it is then.

Thanks.
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Old 08-12-2019, 18:56   #4
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Re: AIS VHF/UHF Antenna

let me just park this here . . . .

Stan Honey recommendations on ais/vhf antenna systems

https://sas.cruisingclub.org/node/388
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Old 08-12-2019, 19:04   #5
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Re: AIS VHF/UHF Antenna

Quote:
Originally Posted by Breaking Waves View Post
let me just park this here . . . .

Stan Honey recommendations on ais/vhf antenna systems

https://sas.cruisingclub.org/node/388

I am not cruising in America and I dont have a mast
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Old 08-12-2019, 19:17   #6
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AIS VHF/UHF Antenna

You can pretty much group any little short antenna with a rubber ducky handheld antenna, meaning that yes they do work, just they donít work very well.
Itís surprising how well a handheld radio works when itís connected to a high mounted full size antenna
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Old 16-12-2019, 06:25   #7
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Re: AIS VHF/UHF Antenna

Yes, it can work. But since the gain isn't mentioned, nor the VSWR, I would never buy it. These antennas designs are commonly used in the 500-3000 MHz ranges for cellular telephone signals. Before we would ever use one in our systems for measuring cellular networks, we would get performance plots in azimuth and elevation vs frequency. This one shows a low gain across a very, very broad frequency range. Note the elevation is 0 degrees (horizon) in this plot. That would be your primary concern, but due to boat heel, you should be concerned also with +/-40 degrees.

https://www.dropbox.com/s/26lwnnjq06...qGain.jpg?dl=0
The same antenna, now plotted in a 3D plot of Azimuth, Elevation, and Gain at a single frequency. Note that the gain is optimized for +30 to +60 degree elevations - that's for a car driving around below the cell site antennas. It still performs ok from -60 to +30 elevation, but there is a considerable loss of gain, especially below 0 degrees. Your antenna is likely to have similar characteristics.

https://www.dropbox.com/s/ff9wdbfwm2...in800.jpg?dl=0
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