AIS, VHF antenna splitter and diplexer

[amiraya]

Hi,

I'm planning to install an AIS in my yacht. I have no extra space on the pushpit and consequently needs an antenna splitter.

My current VHF installatin is made with a diplexer to be able to use the same aerial for my FM radio and my VHF (see attached picture).

May I attach an AIS (with integrated VHF splitter) directly to the com port on the diplexer ? or do I need a new VHF splitter with both AIS, FM and VHF connectors.


/Lars, Sthlm, Sweden

 

[lenseman]

Hi,

I'm planning to install an AIS in my yacht. I have no extra space on the pushpit and consequently needs an antenna splitter.

My current VHF installatin is made with a diplexer to be able to use the same aerial for my FM radio and my VHF (see attached picture).

May I attach an AIS (with integrated VHF splitter) directly to the com port on the diplexer ? or do I need a new VHF splitter with both AIS, FM and VHF connectors.


/Lars, Sthlm, Sweden

Hiya Lars - welcome to the YBW forums.

The diplexer comprises two band-pass filters, one at ~100MHz and the other at ~156MHz and this allows the two signals, VHF FM and VHF Marine, to be separated and go to the correct devices.

The AIS, whether it is a receive only or a Class B AIS, receives and or transmits at about 160MHz and as such occupies the same part of the RF spectrum as the VHF marine tranceiver. If you connected the AIS to the same diplexer as the VHF marine transceiver, you will probably overload the front end of the AIS and destroy the tiny RF FET's (RF Field Effect Transistors).

You will need no special positioning for the AIS antenna than to be high in the cabin roof as long as the cabin is not steel but comprises GRP, plastic or wood. Keep the AIS antenna some distance from the VHF Marine tranceiver and you will have no problems, I recommend a minumum of one metre (-30dB).

You can place the AIS antenna in the lazarette lockers, again, as long as they are plastic or fibreglass.

Please let us know how you get on.

 

[William_H]

Splitter for VHF

As said it is tricky to split a VHF antenna to AIS receiver. You need an extra antenna.
I would suggest you try the AIS with just a piece of wire pushed into the antenna socket. It should be 17 inches long 43 cms and taped up to vertical inside the cabin.(assuming boat is f/g) You may well be saitisfied with the results. You don't need long range for AIS. If that does not work well enough then you should try to find a place outside and as high as possible for the antenna. olewill

 

[Playtime]

Hi,

I'm planning to install an AIS in my yacht. I have no extra space on the pushpit and consequently needs an antenna splitter.

My current VHF installatin is made with a diplexer to be able to use the same aerial for my FM radio and my VHF (see attached picture).

May I attach an AIS (with integrated VHF splitter) directly to the com port on the diplexer ? or do I need a new VHF splitter with both AIS, FM and VHF connectors.


/Lars, Sthlm, Sweden

If a second aerial really is a problem and you can't get it to work as per the suggestions above, the 'proper' solution is one of these EasySplit. Not cheap but would do all you require from one aerial.

 

[purplerobbie]

Isn't it a duplexer you need as a diplexer is only for receiving?
If not what is the difference?

Rob

 

[BlueChip]

Hi,

I'm planning to install an AIS in my yacht. I have no extra space on the pushpit and consequently needs an antenna splitter.

My current VHF installatin is made with a diplexer to be able to use the same aerial for my FM radio and my VHF (see attached picture).

May I attach an AIS (with integrated VHF splitter) directly to the com port on the diplexer ? or do I need a new VHF splitter with both AIS, FM and VHF connectors.


/Lars, Sthlm, Sweden

In your position I would take the antenna signal through the AIS splitter and then pass the VHF signal through your VHF diplexer.

 

[Ex-SolentBoy]

My AIS aerial is in the lazarette locker - works perfectly with good range.

 

[amiraya]

Thanks for the answerrs.

I've followed several threads of the pros / cons of a second VHF aerial and a home made aerial might work, though I've got no space for it.

My question is it possible to connect an AIS with an internal splitter like this one

http://www.yachtbits.com/comar_syst...ombined_ais_receiver_and_antenna_splitter.php

to the com port of the diplexer.

This saves me a lot of installation pain as I only need connect it between my VHF and multiplexer.

/Lars

 

[st599]

In your position I would take the antenna signal through the AIS splitter and then pass the VHF signal through your VHF diplexer.

Knocking reception on the VHF down 3dB and inserting a second failure point.

 

[lenseman]

Knocking reception on the VHF down 3dB and inserting a second failure point.

It's no good telling him, he obviously want to spend £255 unnecessarily.

As a radio engineer I fully agree with you regarding losses due to insertion and for anyone who does not appreciate what 3dB means, it refers to a level of loss, in RF terms, which is half the power available [10 log 2]. This is a big loss!

Ho-hum

 

[DaHobbit]

really!

Reading some of the replies stated here, I was so frustrated at the some of the comments that I felt the need to register just to say this. The answer is no, what your trying to do is use a wait for it FM band splitter. This is designed to receive FM radio signals (the same as you might receive in your car) using the same antenna as your VHF.

The best piece of advice I can offer is the following
a) Don't stick a piece of wire into the antenna socket and trim it to 43cm. what a load of garbage.
b) Do take you antenna out of the lazarette, why you would keep one there god only knows.
c) Do listen to the advise given about DB losses, if you dont understand this research it, its not hard and -3db loss is a massive amount, no matter what any hack tells you.
d) Cost the price of a splitter and compare it to a cheap 3db antenna eg, an ALAN SHARK 3 sells about 30euros witch cable and connectors

Job done.