Re: [Amel Yacht Owners] Range of AIS

Herbert Lackner


Trying to summarize:


Receiving mode:

·         General the splitter is splitting the signal to two (or more) receivers.  If the signal - that has been splittet up – is not amplified again you loose 3dB (50% -  because you split it up for two receivers). 

·         Most oft he modern splitters are active splitters that have a built in amplifier, need power, and will amplify the splitted signal so that in the end no signal reduction should be on both (or more) receivers

·         Anyway there will be some signal loss because of additional connectors… that cannot be restored through amplifying


Sending Mode:

·         The splitter has to make sure that only one device sends at one time. In general they are designed in such a way, that the VHF signal has priority, that means that the AIS is only allowed to transmit if the VHF is not sending.


Splitter or no splitter:

·         When using an active splitter there should be no noteworthy difference between splitter or no splitter in transmitting or receiving

·         From a security point of view it is an additional piece of electronic that can fail.  If so the decision hast o be made if VHF or AIS hast o be used, because only one of them can work. According to murphys law this can occur in a situation where nobody wants to remove the VHF /AIS cover to change the cables…

·         From a „ease of installation“ point it is much easier to install the splitter because its just connecting it, ready

·         Considering the costs it does not make a big difference (splitter is a little bit more expensive).


So, in the end, it is just the question if more reliability or additional installation effort is more important.


On our Santorin we use a Banten active splitter and a comar AIS class B transponder with one antenna without any receiving problems, but sometimes the AIS is not able to transmit and sends an Alarm. I could not find out if that is due to splitter problems but I will change this installation abyway in this year when we change the running rigging and service the mast and install an additional antenna on the mizzen for the AIS. I will keep the Splitter as a spare part, if fore any reason then one oft he antennas will fail I can still go back to the current situation with AIS and VHF on one antenna.


Fair winds



Kali Mera, SN120






Von: amelyachtowners@... [mailto:amelyachtowners@...] Im Auftrag von Patrick Mcaneny
Gesendet: Sonntag, 23. März 2014 12:34
An: amelyachtowners@...
Betreff: Re: [Amel Yacht Owners] Range of AIS



Bob, That's interesting, I was told there would be a loss by the rep. for Garmin , approx. 2db, which was their argument for a dedicated antenna. I just did not and still don't understand why you have a loss assuming good connections and the antenna only servicing one unit at a time either vhf or ais.  Thanks, Pat

-----Original Message-----
From: drbobgray <drbobgray@...>
To: amelyachtowners <amelyachtowners@...>
Sent: Sat, Mar 22, 2014 4:08 pm
Subject: RE: [Amel Yacht Owners] Range of AIS


I'm new to this users group and joined to listen and learn all about the Amel's while my family and I search for a well-maintained used SM53 to buy and use in the Great Lakes.

Here's some theoretical numbers that I've calculated which may may be helpful in understanding what happens when using a 2-way splitter and a 3-way splitter:

2-way splitter...your theoretical insertion loss will be -3dB which is a 50% reduction.

3-way splitter...your theoretical insertion loss will be -4.77dB which is a 67% reduction.


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