AIS Marine Antennas

[VK2KRR]

Thought it would be good for people to share what antennas there using for AIS Marine reception.

But also I have a question about modifying a 50 MHz yagi to work on 162 MHz.

I have an M2 6M7 yagi with damaged elements which im not using, was wondering if this could be modified to be resonant at 162 MHz?

The boom is 26 foot. It has a T match and coax balun. I'd like to try make up the most gain I can on the given boom length. Going from 50 MHz to 162 MHz should be able to add a number of extra elements.
The coax balun is 75 ohm Belden cable, can get the exact part number if required.

The wavelength of 162 MHz is about 1.85 m. So a 26 ft boom would make the antenna about 4.2 wavelengths.

Could any antenna guru's pls calculate number of elements that would fit on this boom, and optimal spacing and element lengths gain figues ?

Here is a photo of part of the boom and the existing driven element.

yagi

[VK2GOM]

Hi Leigh, have a look on the Yagi designer software by VK5DJ. The software is easy to use and produces all dimensions required for any number of elements on any calculated frequency.

http://www.vk5dj.com/

73 - Rob VK2GOM / G0MOH

[VK2KRR]

Hi Rob,

Tnx for the reply. With the yagi calculator, it asks for 'dipole bend dia' and 'gap at feed point'. I dont have a folded dipole, but I see in the results, it mentions a straight dipole measurement, would I just use that measurement?

Also, it says 'Bonded THROUGH metal boom', the elements on this yagi are bonded but sitting ON the boom, does that matter? or should it just be treated same as bonded though boom ?

Perhaps I should just drill then through the boom anyway?

[VK2FAK]

Hi all....

Won't a high gain beam restrict your opportunity to possibly pick up openings in other directions...

I would have thought maybe a high gain vertical that could be put on top of one your towers, something like a Coaxial Collinear...it would be around 8m long which they say can have gain up in the order of 9db....and on your tower would get some height gain also..

Construction would be reasonable easy....laying your hands on bits and pieces and the fiberglass tubing another story..

John

[VK2KRR]

Hi John

I think im that far away from the coastal areas that I need a directional antenna to get the gain required. Also my ocean coverage will only be from Melbourne around to Adelaide and the Bight. Most times Im going to want to know what going on with signals out in the Bight, and wont really be concerned with signals in Melbourne port. When there is no propagation from the Bight direction, I could just beam it into the Melbourne port for something to keep it active.
So hence I need to focus the majority of the beam pattern into the Great Aust Bight direction.

Thanks for the thought though

[VK2GOM]

Hi Leigh, sitting on the boom is probably near enough bonded through boom for the purposes of any factoring and a receive-only antenna. As regards your T match, you could probably modify this to become a folded dipole, although you could just use the straight non-folded dipole, add the proper balun as per the design in the program, and do away with the T match all together. You already have the boom mounted box for SO239 input. I assume the box will pry / unscrew apart?

Just play around with the number of directors until you come up with something that will fit nicely on your boom.

The beauty of the program is you can feed in dimensions for whatever element/boom material you can find, and it does all the length factoring for you.

73 - Rob VK2GOM / G0MOH

[VK2KRR]

Hi Rob,

Its an N connector input, the box doesn't come appart, its a solid machined aluminium piece. It unscrews from the boom but thats about it. There is an inspection screw in bung under it.

I'll see what I can come up with.

[VK5PJ]

Leigh,
from the photo you uploaded, it would appear to be a very standard M2 T match, you now have several problems with re-using this setup.

Hi Rob,
Its an N connector input, the box doesn't come appart, its a solid machined aluminium piece. It unscrews from the boom but thats about it. There is an inspection screw in bung under it.
I'll see what I can come up with.

I would suggest you find and existing 144 MHz yagi and do a bit of slicing and dicing or have some one drill you a boom and fit a basic open dipole feed.

By the way, what is wrong with that M2 yagi? do you want to sell it instead of hacking it around as the boom and T match would be extremely valuable for some one wanting to get onto 6mx.. I would offer you a custom built 162MHz yagi but transporting it is the problem as mine do not break down into small lengths.

Peter

[VK4AJL]

I just use a mobile antenna and a nasa ais receiver signals rising at the moment
in Central Qld local port Hay point coal termial must be good tropo at the moment am about 30km approx away 47k by road George vk4ajl@wia.org.au mainetrafic.com shows info not my site

[VK2KRR]

VK4AJL, what town is that near?

[VK4GHZ]

Being inland, an omni is wasted here.

I've emailed M2.
They list a number of VHF marine yagis, but there are no details on their website... just "call".
Of particular interest is the "160-7", a 10dBd yagi on a 2.43m boom.

Will post back the response.

[VK2KRR]

Hi Adam,

Mine are actually the 162-10 design.

[ZL3TY]

My antenna is a commercial 150MHz 5 el yagi. I used Yagimax to recalculate element lengths for 162MHz, leaving spacings as they were for 150MHz. The feed is still around 50ohms, into a mast-mounted preamp, then fed with RG6 (75ohm) cable, approx 20m. Calculated antenna gain is about 8dB and it is pointed at VK2/4. Sea horizon here is about 100 degrees so high gain/narrow beamwidth would be no good. The antenna works, best DX is 2400km+, with signals received from all over the Tasman sea.

[VK4GHZ]

I've emailed M2.
They list a number of VHF marine yagis, but there are no details on their website... just "call".
Of particular interest is the "160-7", a 10dBd yagi on a 2.43m boom.

Will post back the response.

Hi Jason

Just wondering if M2 are producing yagis for the 160 MHz VHF marine band?
With the demise of analogue television, AIS VHF marine tracking is becoming very popular in Australia as a 2m tropo indicator.

I’ve had a look on the commercial section of the M2 website, and there isn’t much information about this, just “call”.
I’m particularly interested in model # 160-7.

Could you please provide indicative pricing, lead time, and estimated postage to Brisbane 4000, Australia.

Cheers,
Adam

Jason replied with:

Hello Adam,
That’s a great question and a unique use for these antennas.

The list price for a single antenna is US $350, and shipping via DHL will be the most economical at US $138.

However, if you find a few friends who would like to make a quantity purchase, we can offer a discount of 10% for 5 or more if purchased at the same time and shipped together.

Regards,
Jason Boyer, N6EY
Amateur Marketing and Sales

So for a one-off, that's price prohibitive... pity M2 aren't in Australia, as freight is the killer.

[VK2GOM]

Adam,

Why not design one in one of the Yagi design programs, and build - It's literally an afternoon project.

I have built a few different Yagi's from the VK5DJ software.

73 - Rob VK2GOM / GW0MOH

[VK4GHZ]

Why not design one in one of the Yagi design programs, and build - It's literally an afternoon project.
I have built a few different Yagi's from the VK5DJ software.

Good idea, will be fun to play with!
Have downloaded from http://www.vk5dj.com/yagi.html, and installed on the other PC.

I like the option of square boom, makes it much easier to drill along.
At least your elements will only be skew whiff along the element plane, instead of being all over the shop!

7 elements might be a good place to start?
I have an M2 2M7 for 2m field use, and that sized package is a very manageable.

[VK2KRR]

Adam,

Hav u tried to listen on 161.975 or 162.025 (the AIS Freqs) to see if you already hear anything from home, say with a 2m vertical and IC910 on FM ? What ur looking for are high pitched clicking type noises, just to see if u can hear anything at all with a non resonant antenna for starters to see what ur up against.

Good thing about AIS marine tracking is that the yagis can be built very narrow in bandwidth ability and u can really build for high gain at 162.000 and you only need to cover 161.975 and 162.025. If u can get a really good narrow SWR or return loss it will also help reduce interference from close by strong signals above and below the freq range.

[VK2GOM]

Just a tip too, if you have a mini pipe bender (got mine from a market for about $10), work out its bend diameter, and do your folded dipole that diameter. Saves messing around, and far easier to make. The baluns are simple too. Choice of many coaxes depending on what's in the junk box! I've used UT141 for a 23cm Yagi balun, but down at 161MHz even RG58 would be fine.

Through boom mounting of elements is quickest, and secure with a single small self tapper (or a long rivet) to go through just the top of the boom and into one wall of the element. No need to go all the way through. Also makes it easier to line everything up with a folded dipole that goes either side of the boom.

The VK5DJ software seems good, as you can completely customise the design based on the materials you have, or can obtain.

73 - Rob VK2GOM / GW0MOH

[VK5AKK]

I made a 10 element AIS yagi using the VK5DJ design sofware, from old antenna bits laying around here. Antenna has a folded dipole feed and all elements insulated above the boom. I was first worried about reception of side lobes being a problem but it works better than the 17 element collinear that it replaced. Best reception distance so far is 3250 Km over inland Oz and out 600km NW of Exmouth. Antenna is fixed beaming at Albany.
Cheers
Phil

[G8VOQ]

Hi. I know practically nothing about AIS. Might like to get into it though later this year.

As to Marine AIS antennas here is a 3 element one:

http://www.ebay.co.uk/itm/3el-AIS-Anten ... 43b62ef26a

Sells for £79.95 or about $116 Australian. No idea of postage.

Sold by: http://www.innovantennas.com/

Rich