Which antenna for AIS transponder/receiver

[slawosz]

Hi,
I aquired an AIS transponder (Onwa Chartplotter). I need to buy an antenna. What is the best (or best budget) choice?

 

[Daverw]

Just use any vhf antenna

 

[Rappey]

Shakespear do one tuned for ais. It's around 29mm shorter than a vhf tuned antenna.
Shakespeare 0.9m S/S Squatty Body AIS Whip Antenna (818-5215-AIS)

 

[Stemar]

Out of curiosity, could I use my AIS antenna for a VHF radio (R1, 2, 3,4, etc)? Would either signal suffer noticeably?

 

[slawosz]

Shakespear do one tuned for ais. It's around 29mm shorter than a vhf tuned antenna.
Shakespeare 0.9m S/S Squatty Body AIS Whip Antenna (818-5215-AIS)

Forgive me stupid question - does it matter if I will install the antenna on the rail instead on the mast even though it says in the description 'top mast antenna'?

 

[tillergirl]

Slawosz

I forgot to tell you it is better to have the right antenna. It needs a diffferent range of frequencies to a standard VHF.

 

[johnalison]

Forgive me stupid question - does it matter if I will install the antenna on the rail instead on the mast even though it says in the description 'top mast antenna'?

It will just limit the range from perhaps 20-40 miles to 10-20, which may be adequate for most conditions.

 

[savageseadog]

Slawosz

I forgot to tell you it is better to have the right antenna. It needs a diffferent range of frequencies to a standard VHF.

AIS frequencies are at the top end of VHF marine frequencies. A normal VHF aerial will have a length suited to the middle of the VHF frequencies which extend from 156 to about 157.4Mhz. AIS runs at 161-162 Mhz approx which is a slightly shorter wavelength hence the optimum AIS antenna would be slightly shorter. Without doing the calculations a standard marine VHF antenna would not be optimum but practically good enough.

 

[vyv_cox]

Forgive me stupid question - does it matter if I will install the antenna on the rail instead on the mast even though it says in the description 'top mast antenna'?

Mine is on my stern arch about 3 metres above the water. It works fine, detects vessels over 20 miles away.

 

[Refueler]

Hi,
I aquired an AIS transponder (Onwa Chartplotter). I need to buy an antenna. What is the best (or best budget) choice?

Standard VHF antenna will be good enough. Technically a tuned AIS antenna is a few cms shorter ... but the practical difference is negligible.

 

[Roberto]

Maybe not "any" vhf antenna: these are SWRs for different VHF antennas along the band, some are definitely best avoided for AIS.
(Image taken from the internet a long time ago, no idea of the source)

 

[Refueler]

Maybe not "any" vhf antenna: these are SWRs for different VHF antennas along the band, some are definitely best avoided for AIS.
(Image taken from the internet a long time ago, no idea of the source)

View attachment 136837

So the answer is to calculate the optimum length - but then how to adjust for 'loaded' ??

 

[ithet]

Out of curiosity, could I use my AIS antenna for a VHF radio (R1, 2, 3,4, etc)? Would either signal suffer noticeably?

I do just that. In fact my Vesper AIS splitter has a dedicated FM connector which is connected to the car type radio. Works really well.

 

[Stemar]

I do just that. In fact my Vesper AIS splitter has a dedicated FM connector which is connected to the car type radio. Works really well.

Thank you. Since both are receive only, Am I right in thinking that I don't need a splitter, but could just run another cable to the bottom of the antenna?