Aerial for DSC VHF and AIS receiver

[crms]

Hi,

AIS operates on 162MHz which is in the maritime VHF band, I think. Can I split the VHF aerial line to feed both a DSC VHF set and a stand alone AIS receiver??? - this receiver in particular
http://www.allgadgets.co.uk/ag/product.asp?dept%5Fid=1&pf%5Fid=AG3933

TVMIA

 

[Colvic Watson]

I asked Nasa about this last week and they said no, needs a separate ariel. /forums/images/graemlins/frown.gif
As the AIS doesn't come with one, that means it actually costs about £35 more.

 

[ShipsWoofy]

But you should 'really' be carrying a spare aerial in case you lose the mast anyhow.

Fix your spare to the pushpit and connect to the AIS. Have enough spare lead to get from AIS receiver to ships VHF and you have rigged a good jury aerial for the cost of a splitter.

 

[Colvic Watson]

Makes great sense to do that (would save going up the mast for a start), but AIS is also line of sight only as it works on VHF, so would it benefit from having the aerial higher up? I think AIS displays up to 16nm away.

 

[Phoenix of Hamble]

So stick your emergency antenna on a pole (perhaps shared with your GPS antenna)... that way you'd get something like 8 miles range, which is more than enough I would have thought....

 

[muddyfeet]

crms - I looked into this situation following NASA advice and fitted the AIS set to a pushpit mounted standard VHF ariel.This finds vessels at least 8 miles away (even when berthed in the marina at low water with all ensuing obstructions!)
I have enough cable to use the ariel in emergency for the radio, but it would be a "real" emergency as it would require unscrewing panels etc. to get behind both sets - but it could be done.
I am about to give the set-up its first N.Sea crossing and am looking forward to the first serious test!
Hope this helps.

 

[Oldhand]

If you split your current VHF antenna between the VHF and the AIS "engine", when you tried to transmit on your VHF you would probably "blow-up" both peices of equipment!

 

[peterb]

We have the normal masthead VHF aerial with an 'emergency' aerial mounted on a post on the stern. We used to have a coaxial switch mounted on the main switch panel, so that connection of the emergency aerial just meant turning a switch.

We've just added a second switch so that the emergency aerial can feed the AIS. If we lose the main aerial, then we lose the AIS, but that's acceptable in an emergency.

Experience has shown that even with the aerial mounted on the pushpit we can still get signals from ships up to 20 miles away. Remember that the 'visual range' has two elements: your horizon distance and the ship's; the latter is likely to be much greater than yours.

Incidentally, we've been very pleased with the performance of our 'AIS Radar'. Just one gripe; it only comes in North-up mode, and there is no heading marker. So having determined which 'echo' is likely to be a problem, you then have to relate this to the ships around you by comparing their positions on the display and an imaginary line giving your heading. It would be so much easier if the display gave a heading marker.

 

[hightech]

An unwritten trade rule is "one aerial for one product".

Basically if you connect more than one receiver/transmitter to an aerial expect problems. This includes the use of "so called" splitters and the like, one way or another you are compromising and something will suffer.

The day you need your VHF or DSC to send your distress signal may be the day it decides to go on the fritz!!

Hightech

 

[crms]

Thanks for pointing out the obvious problem of VHF transmissions. I am planning to feed the AIS signal into a laptop and use Sea Clear chartplotter (fully featured and amazingly free from http://sping.com/seaclear/index.htm) to display charts with AIS info overlaid.

 

[wiggy]

just done the same thing absolutely fantastic, get the newest version of seaclear and its got collision vectors and guard zones, incredible, I used it in the solent this weekend. No real need as fantastic weather but a good opportunity to test the setup and get used to using it, have fun.

 

[tarik]

Could you pse check the site quoted - comes up 'unable to locate'

Cheers David

 

[Hoolie]

Delete the trailing bracket from the site address! /forums/images/graemlins/smile.gif

 

[Amphitrite]

You definitely need a second aerial for your AIS receiver. If you use a shared antenna with your VHF, you will blow up the AIS receiver with the first outgoing VHF call. However, an emergency aerial works great and gives you quite a good range.... (but not to be compared with a mast-top aerial).

Cheers, Holger

 

[audouin]

Distance between AIS and VHF ariels

You definitely need a second aerial for your AIS receiver. If you use a shared antenna with your VHF, you will blow up the AIS receiver with the first outgoing VHF call. However, an emergency aerial works great and gives you quite a good range.... (but not to be compared with a mast-top aerial).

Cheers, Holger

I wonder if you can help. I have placed a separate new ariel up the mast to run my AIS but have now been told the AIS annenta should be atleast 1 metre away from my VHF ariel or it blow the system, when transmiting DSC call. do you know or anyone -if this is true?