Aerials for AIS

[Cantata]

Radio experts please advise!
I have an AIS transceiver working well, using a long fibreglass whip aerial that came with the boat, mounted on the stern rail. As far as I know it's a regular VHF aerial. My VHF itself uses a separate aerial.
It's deteriorating badly now so I need to replace it, and I've ordered one much the same, that was advertised as a VHF aerial.
I'm now wondering if I've done the right thing, seeing there are specific AIS aerials advertised. Would I get such better performance from an aerial designed for AIS use, that I ought to return the new VHF-type aerial that I've bought?

 

[[194224]]

An AIS specific antenna is tuned around the two VHF frequencies involved (c. 162MHz). A Marine VHF antenna needs to receive and transmit a wider range of VHF frequencies (c. 156-157MHz), tuning is normally based around CH16 (156.8MHz). Those frequencies are close enough to mean that a VHF antenna will work well with AIS although it is not optimal. Whether the possible loss of performance is truly significant under most circumstances, not sure.

 

[PaulRainbow]

Radio experts please advise!
I have an AIS transceiver working well, using a long fibreglass whip aerial that came with the boat, mounted on the stern rail. As far as I know it's a regular VHF aerial. My VHF itself uses a separate aerial.
It's deteriorating badly now so I need to replace it, and I've ordered one much the same, that was advertised as a VHF aerial.
I'm now wondering if I've done the right thing, seeing there are specific AIS aerials advertised. Would I get such better performance from an aerial designed for AIS use, that I ought to return the new VHF-type aerial that I've bought?

I doubt you'll notice a difference, wouldn't worry about it.

 

[Daverw]

When I replaced my AIS whip last year, I just used my spare vhf one, tuned it to slightly higher centre frequency by chopping about 7mm off the whip. I do have antenna analyser so made this easy.

 

[ylop]

If any performance gain you would get from an antennae tuned to the specific AIS frequency mattered you’d not mount it on the push pit - as height matters much more. I have a little helical stubby from an old vhf that seems to do a reasonable job for anything close enough for me to be worried about.

 

[William_H]

Lastly if you do lose a mast or have a failure of VHF com antenna you should make arrangements to easily use the AIS antenna. In which case antenna will be optimal. As said range and performance is not so critical in AIS. You don't want signals from a long way away. ol'will

 

[geem]

We mounted a conventional Metz vhf antenna on the top of the mizzen mast. Range is exceptional

 

[Cantata]

Thanks all, very helpful, and as a result I shall carry on and fit the aerial that I've ordered.

 

[Momac]

I have the Metz antennas for both VHF and AIS but really there is no different physically to the vhf antenna by the same manufacturer so I suspect no difference in any other way other than marketing.
Last time I looked the Metz was not available in the UK but there alternatives like Shakespeare

 

[Refueler]

When I replaced my AIS whip last year, I just used my spare vhf one, tuned it to slightly higher centre frequency by chopping about 7mm off the whip. I do have antenna analyser so made this easy.

I doubt very much you would actually be able to detect any difference.

 

[Refueler]

We mounted a conventional Metz vhf antenna on the top of the mizzen mast. Range is exceptional

Height is 'might' ..... QED

 

[Sandy]

Radio experts please advise!
I have an AIS transceiver working well, using a long fibreglass whip aerial that came with the boat, mounted on the stern rail. As far as I know it's a regular VHF aerial. My VHF itself uses a separate aerial.
It's deteriorating badly now so I need to replace it, and I've ordered one much the same, that was advertised as a VHF aerial.
I'm now wondering if I've done the right thing, seeing there are specific AIS aerials advertised. Would I get such better performance from an aerial designed for AIS use, that I ought to return the new VHF-type aerial that I've bought?

How far do you need to see?

What risk have you colliding with a vessel 20/30/40/50 NM away?

 

[geem]

How far do you need to see?

What risk have you colliding with a vessel 20/30/40/50 NM away?

It's not just seeing, it's being seen. Class B is only 2W transmission power. A good antenna is beneficial. We often only see other yachts at 2 or 3 miles. Friends reported we were visible at 13nm. When crossing Biscay shipping lanes, its nice to know that huge ships see us in good time. They don't alter course so easily

 

[Momac]

It's not just seeing, it's being seen. Class B is only 2W transmission power. A good antenna is beneficial. We often only see other yachts at 2 or 3 miles. Friends reported we were visible at 13nm. When crossing Biscay shipping lanes, its nice to know that huge ships see us in good time. They don't alter course so easily

Would you expect a ship to alter course for you if some miles off the shore?

 

[Refueler]

Would you expect a ship to alter course for you if some miles off the shore?

What sort of question is that ??

Sorry - but I cannot see your point when replying to a valid post ....

It's not just seeing, it's being seen. Class B is only 2W transmission power. A good antenna is beneficial. We often only see other yachts at 2 or 3 miles. Friends reported we were visible at 13nm. When crossing Biscay shipping lanes, its nice to know that huge ships see us in good time. They don't alter course so easily

Class B+ is now 5W ... but that's beside the point ... HEIGHT is MIGHT as I said before .. whether 2 or 5W .. if you get your antenna high as in masthead - you will be seen at a greater distance than pushpit rail height - same goes for you to receive !

My tests of my system .. I rec;'d 4 targets via rail antenna ... but 21 targets at masthead antenna ... QED.

 

[Momac]

What sort of question is that ??

Sorry - but I cannot see your point when replying to a valid post ....

Just wanting to know if the poster expects ships to alter course . It seems implied the ship might do so if he is seen at longer range .
I thought it was a valid question.
Have a nice day

 

[Refueler]

Just wanting to know if the poster expects ships to alter course . It seems implied the ship might do so if he is seen at longer range .
I thought it was a valid question.
Have a nice day

Your post was simplistic to extent it made no sense ...

Would you expect a ship to alter course for you if some miles off the shore?

If there is no constraint of draft / shipping lane - then the answer is YES .. of course he would alter if ColRegs apply ..

Maybe a little more detail in the question might be an idea ??

 

[Momac]

Your post was simplistic to extent it made no sense ...



If there is no constraint of draft / shipping lane - then the answer is YES .. of course he would alter if ColRegs apply ..

Maybe a little more detail in the question might be an idea ??

My interpretation of Colregs is you (as a yacht or motorboat) should keep out of the way of ships .
How does the ship seeing the yacht earlier help with that ?

 

[Refueler]

My interpretation of Colregs is you (as a yacht or motorboat) should keep out of the way of ships .
How does the ship seeing the yacht earlier help with that ?

Please tell me you are having a laugh ......

Did you not read the bit that said : "of course he would alter if ColRegs apply "

As an ex Bridge Watchkeeper of ships from coastal to super tonnage .. I am actually offended by your lack of understanding of Colregs.

 

[Pye_End]

My interpretation of Colregs is you (as a yacht or motorboat) should keep out of the way of ships .
How does the ship seeing the yacht earlier help with that ?

Incorrect interpretation.

Ships will almost always give way if that is their duty, particularly when offshore. It's the ones that seemingly aren't keeping watch that you need to take a bit more care over!

I don't know how many miles they like to make course adjustments, but without a transponder on a yacht they almost all seem to do the right thing in good time. 8 miles with the antenna on the guardrail is plenty. Guard zone of 4 miles is more than adequate offshore.