AIS Aeriel Question?

[xeitosaphil]

Having just acquired a Digital Yacht AIS Dual Chanel receiver , and having read many posts on the forum about Splitters vs Dedicated Aerials , Mast vs Pushpit mounting. I have decided to mount the aerial on the stern push pit, as I like the idea of a back up VHF aerial which is an added bonus.
My question is, would a good VHF aerial like a Metz Manta VHF 34" whip Aerial mounted on the pushpit be as good or worse than a new generation dedicated AIS antenna such as a Glomex AIS Marine Antenna RA111AIS or DIGITAL YACHT AA10 AIS TUNED VHF ANTENNA, or a Digital Yacht HA156A Tuned AIS stub /Helical Antenna

The Metz Manta is a 1/2 Wave, with a •Frequency range 156 - 163 MHz which is 870mm o/a High
The Glowmex has a dedicated Frequency range: 161.975 MHz – 162.025 MHz which is 200mm o/a High
The Digital Yacht is a ¼ wave with a dedicated frequency (160-162 MHz) and is 470mm o/a High
I do like the idea of a small compact Aerial but would like to optimize the performance and range?
Also how would a dedicated AIS aerial perform when in VHF distress mode?
There is not a lot of difference in any of the prices, just wondered which was the best option ,not knowing a lot about Radio frequencies and performance?

 

[neale]

There will be very little difference between them, not enough for you to notice. I would go with whichever one you felt was best suited to the task and to your budget.

Performance, as in distance, is more a matter of height. The higher the aerial, the further you will transmit.

 

[Talbot]

I use a standard 1.1m whip from JGtech on my pulpit. It has a PL259 plug on the bottom, which means that I can use it as an emergency VHF aerial if needed.

On my previous boat I initially used a much shorter VHF aerial on my pulpit, and was very disappointed with its range. I changed to a 1.1m whip and achieved much better results.

 

[lustyd]

There will be very little difference between them, not enough for you to notice. I would go with whichever one you felt was best suited to the task and to your budget.

Performance, as in distance, is more a matter of height. The higher the aerial, the further you will transmit.

Not when using it as a backup VHF! The dedicated one by it's nature is designed for the frequency of AIS and therefore will not be as good for VHF.

 

[neale]

Not when using it as a backup VHF! The dedicated one by it's nature is designed for the frequency of AIS and therefore will not be as good for VHF.

I accepted that, but said it would not really be a noticable differece. I stand by that. Bearing in mind that this aeriel will be used 99.999999999999999% of the time for AIS and possibly never for VHF communications I would get whichever aeriel suits the op best.

 

[Salty John]

Metz makes an optimised AIS antenna which will be on sale in about two weeks. It is pretuned to 162MHz and has sufficient bandwidth to function as a back up radio antenna.

However, we continue to recommend the Metz Manta for AIS where it is to be the backup to the radio antenna. It performs well over the whole range.

Most VHF antennas are centered on 156.80MHz and have sufficient bandwidth to handle the AIS frequencies, around 162MHz. Some antennas will have a more noticeable fall off at the end of the range than others, but all will handle both frequencies.

 

[lustyd]

The Glowmex has a dedicated Frequency range: 161.975 MHz – 162.025 MHz which is 200mm o/a High
The Digital Yacht is a ¼ wave with a dedicated frequency (160-162 MHz) and is 470mm o/a High

I accepted that, but said it would not really be a noticable differece. I stand by that. Bearing in mind that this aeriel will be used 99.999999999999999% of the time for AIS and possibly never for VHF communications I would get whichever aeriel suits the op best.

Channel 16 is 156.800Mhz so I think it may be a problem using an aerial to transmit emergency traffic after a dismasting on an aerial with a range of 160-162Mhz. DSC is on Ch70 (156.525Mhz) so even your red button wouldn't necessarily work.
The key word is dedicated - these are designed solely for use with AIS and not as a backup VHF aerial. Keep in mind that the only time you'll use the backup is when you're needing assistance.

 

[ianfr]

Hi

I can recommend the Metz aerial as available from Salty John.
I have one fitted on the pushpit and it is connected to a NASA ais engine. During a crossing from Ramsgate last year, I was still seeing targets in Harwich! I have an adapter fitted so that I can use it as an emergency aerial if needs be.
This year I have also fitted another Metz at the masthead to replace a manky old Glomex one.

regards

Ian

 

[fireball]

Channel 16 is 156.800Mhz so I think it may be a problem using an aerial to transmit emergency traffic after a dismasting on an aerial with a range of 160-162Mhz. DSC is on Ch70 (156.525Mhz) so even your red button wouldn't necessarily work.
The key word is dedicated - these are designed solely for use with AIS and not as a backup VHF aerial. Keep in mind that the only time you'll use the backup is when you're needing assistance.

Can you clarify your "wouldn't necessarily work" statement please.

I believe the untuned antenna would limit the range of the transmission - so unless there was something wrong with your VHF, it would work - just not with the range you'd get with a tuned antenna.

 

[Martin_J]

When choosing a pulpit mounted aerial for my AIS.. I actually went for one of the Glomex ones that was tall enough so that nobody could fall on it and poke their eye out..

Think I chose about a 1.1m one with the round blue ball type cap at the top.

As others have said.. with the right connector it doubles as a VHF aerial.

 

[Tex]

I have recently fitted a DY AIS receiver with the DIGITAL YACHT AA10 aerial on pushpit.
(Linked to a C70)

I think the results so far are quite acceptable, picking up contacts at least 15 miles away.

 

[whipper_snapper]

Can you clarify your "wouldn't necessarily work" statement please.

I believe the untuned antenna would limit the range of the transmission - so unless there was something wrong with your VHF, it would work - just not with the range you'd get with a tuned antenna.

Not even that, it would slightly reduce the radiated power which for most yachts, especially with pushpit mounted aerials, will make absolutely no difference to the range.

Essentially I think that lustyd is dead wrong and saltyjohn is dead right.

 

[lustyd]

Can you clarify your "wouldn't necessarily work" statement please.

I believe the untuned antenna would limit the range of the transmission - so unless there was something wrong with your VHF, it would work - just not with the range you'd get with a tuned antenna.

Exactly what I said, nobody will offer you a guarantee that the AIS one will work with other VHF channels because it's not designed to do so. I'm interested to hear the results of a radio check over a reasonable distance using one but if you want one that you know will work then a proper emergency aerial would be the way to go. Whether it works properly, partially or appears to work and actually has a range of 30 meters is besides the point.
FWIW Salty John seems to be saying the same thing I am so I fail to see how he's right and I'm wrong.

 

[maxi77]

I have a bog standard VHF antenna on the puishpit for my AIS and it works just fine, and as they are mounted side by side each can use either or using the built in splitter both can use either together. I also have an adapter so that my handheld can use either fixed antenna.

Belt braces and nicky tams

 

[fireball]

Channel 16 is 156.800Mhz so I think it may be a problem using an aerial to transmit emergency traffic after a dismasting on an aerial with a range of 160-162Mhz. DSC is on Ch70 (156.525Mhz) so even your red button wouldn't necessarily work.
The key word is dedicated - these are designed solely for use with AIS and not as a backup VHF aerial. Keep in mind that the only time you'll use the backup is when you're needing assistance.

Exactly what I said, nobody will offer you a guarantee that the AIS one will work with other VHF channels because it's not designed to do so. I'm interested to hear the results of a radio check over a reasonable distance using one but if you want one that you know will work then a proper emergency aerial would be the way to go. Whether it works properly, partially or appears to work and actually has a range of 30 meters is besides the point.
FWIW Salty John seems to be saying the same thing I am so I fail to see how he's right and I'm wrong.

Sorry - you've come on here and basically stated that you wouldn't guarantee that a non-dedicated antenna would work. You've offered nothing technical to backup these concerns - other than a difference in frequency.

Your "range of 30 meters" is misleading to the extreme - and again, no technical or even experience to back that up.

I'm not an RF engineer - never have been, never will be. Like many, I come on here and read technical posts and posts with advice as to what will/won't work and I believe you're on the verge of causing serious doubts in many ppls installations.

FWIW - I have tried a few antennas. I have a standard vtronix hawk antenna on the masthead. This receives Solent Coastguard whilst in Cherbourg and even into the CI's - on a normal day.
If I attach my AIS engine to this I get 35+Nm range - from Chichester Harbour I'm getting targets South West of the IOW. The masthead is ~60' above sea level.

I have a VTronix Rib Raider antenna on the stern pushpit - so not raised at all. This gets me around 15Nm range on AIS. I have tested it with the normal VHF, but have not tested VHF range. I assume the range is going to be ~20Nm, but don't bank on any more than 15.

The other antenna I tried was a Heliflex Stub antenna. this didn't produce good results at all for AIS. We have the same one on the club rib and the range is limited - although this may be to do with relative heights - I have used my vessel (with 60' mast) as a relay on more than one occasion despite being further away from the Rib than the base station.

I understand the concept of tuned antenna - and this is why there are antennas tuned for and marketed as AIS antennas - but AFAIK this doesn't affect their use in the marine VHF band - other than a potential range loss - but I can't quantify that. All I would say is that if it was that marked a difference (30NM to 30meters!) then the standard antenna wouldn't work across the range of channels either - so it can't be that big a difference.

There are many more things that can affect the range of VHF signals - height being the main one.

 

[Quester]

I use a WeatherDock Easy Split FM splitter from my 40' high masthead antenna, splitting to DSCVHF and AIS engine. This works very well for me and gives great AIS range. Then I use a (home made) emergency antenna which I can clip to whatever is left of the boat in an emergency (thoroughly tested after dismasting two years ago).

 

[lustyd]

I have a VTronix Rib Raider antenna on the stern pushpit - so not raised at all. This gets me around 15Nm range on AIS. I have tested it with the normal VHF, but have not tested VHF range. I assume the range is going to be ~20Nm, but don't bank on any more than 15. .

All you've added in this entire post is that you've tested all the combinations except the one I was doubting, and that you assume it would work. Please feel free to try it and let us know - my intention was to cast doubt on people's installations because these things should be tested before you get in trouble, not after. AIS will work with a standard aerial because it's on a standard VHF frequency that standard aerials are designed to work with. The AIS specific ones are for the specific frequency which allows them to be smaller and more compact. The specifications state that it works for a list of frequencies, and the websites of the suppliers don't state that it works for the other frequencies apart from Metz whose aerial is designed for all VHF frequencies. I don't think I ever said that it won't work, just that it might not work. Even if it does there will be a limited range for which there are no figures.
This is very much like me saying that if my mainsheet breaks I can use string to replace it. In that sentence I never said the breaking strain of the string or how well it would function, all you get is a statement that string will hold the boom. I've ignored the fact that the sheet probably broke in a storm and that the string would not allow me to sail, just like with the radio we're ignoring the probable dismasting and that the radio may not even contact a boat a mile away.
I'd love to see YM or someone else test the various aerials and get an answer but until that point I think casting doubt is very much the right course of action rather than telling people it'll work fine.

 

[whipper_snapper]

it'll work fine.

 

[lustyd]

it'll work fine.

Oh well since YOU guarantee it that's fine then...

 

[ianj99]

Any whip aerial will work over a wide range of frequencies but the 'tuned' length is 'technically correct' for only one frequency since the wavelength is derived from the frequency.

However the drop in efficiency for frequencies either side of the tuned one is small otherwise no one aerial would cover the whole marine vhf band. Ditto your TV aerial etc etc

AIS specific aerials are a marketing ploy* - a standard vhf one will work just as well in practice and can double as a backup.

* the extra range if any of an AIS specific one is harldy relevant - what difference does it make if it picks up vessels from an extra few miles distant?

I recently installed a Navicom RT650 vhf with built in AIS and picked up a tanker 58nm away using the mizzen mast mounted vhf aerial. Had I installed a separate ais receiver, I would have fitted a splitter and used the same aerial for both.
Ian