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Old 21-09-2010, 17:02   #16
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I just can't bring myself to spend the money on a new radio so soon.
then buy one of the many AIS standalone receivers or better yet a transponder, youll never reget it.

Dave
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Old 21-09-2010, 17:51   #17
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Originally Posted by svfairwinds View Post
I wish they'd had these 18 months ago when I purchased a new Uniden UM 525. I just can't bring myself to spend the money on a new radio so soon.

I have an old ICOM M100 VHF I'd like to use to receive the AIS data grams. But I need help finding the correct point in the circuit to tap off the signal before it's filtered.

Dave
fair winds
I can understand your hesitation but selling the Uniden and replacing it with a VHF with integrated AIS may be a cheaper option in the long run and save you a hell of a lot of hassles & you will then get an AIS receiver that was built for the job and you can be confident in.
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Old 21-09-2010, 19:58   #18
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You cannot.

A marine VHF modifies (I guess by filtration) the portion of signal you need for successful demodulation.

If you google around the answer is there. But one can buy a VHF receiver that does not screw up the signal too - the problem is a cheap AIS receiver from NASA (approx 200 USD) does the job probably cheaper and better.

Sorry,
b.
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Old 21-09-2010, 20:01   #19
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BTW

The new Standard Horizon VHF receives and demodulates AIS PLUS it has its own screen PLUS it can contact the AIS targets PLUS it has a signal output ...

I will get one for our boat as soon as in range.

barnie
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Old 22-09-2010, 10:36   #20
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You certainly CAN use any old marine VHF to receive AIS packets. I used to use an Icom M100 but now am using an M502 in my shop with output to computer audio input and running the Shipplotter program. Works great. You must tap directly off the discriminator output before audio filtering for this to work.

Eric
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Old 22-09-2010, 11:37   #21
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...output to computer audio input and running the Shipplotter program. Works great. You must tap directly off the discriminator output before audio filtering for this to work.

Eric
Eric : how? a drawing or any sort of diagram would help.

You are talking exactly of the limitation I heard before DISCRIMINATOR - how do you identify it and tap the signal before it?

b.
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Old 22-09-2010, 13:28   #22
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You take the signal AFTER the discriminator which is the demodulated unfiltered signal. You need to find it either by the numbers on the chip, or service manual/schematic. Modern radio's like the M502 have almost all very small surface mounted components that are densely packed. I'm a marine electronics service tech so it's no problem for me but may be very difficult for the inexperienced.

Eric
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Old 23-09-2010, 09:01   #23
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You take the signal AFTER the discriminator which is the demodulated unfiltered signal. You need to find it either by the numbers on the chip, or service manual/schematic.

Eric
OK, can you post any pictures of your set-up or a handmade schematic or anything that would help us thru the maze?

I might be able to get an older VHF here, open it up and use it for AIS signal.

How do you 'tap' the signal - you solder wires or sthg? And then does it go directly into laptop's RS port?

barnie
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Old 23-09-2010, 09:05   #24
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How do you 'tap' the signal...?
No offense, but if you have to ask how to tap the signal, then it is probably not something that you should try on your own. That is, not unless you are "just playing" and would not be at all upset if you destroyed the VHF that you were trying to modify.

As fairbanks56 said, modern radios are pretty tightly packed. Modifying one is not a "beginner" sort of project!
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Old 23-09-2010, 10:51   #25
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No offense, but if you have to ask how to tap the signal, then it is probably not something that you should try on your own.
No offense taken.

I am not going to fool around with my new radio either. I have an older ICOM that I could open up and use.

Pictures, diagram, anything that can help me?

b.
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Old 27-09-2010, 09:50   #26
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I know its an old thread but did you find out about VHF discriminators. If not try AIS on VHF Cheapest AIS SYSTEM for Yachts. Speak to Adrian and tell him Roger Newby sent you.
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Old 27-09-2010, 09:53   #27
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Hi. Speak to Adrian at Cheapest AIS SYSTEM for Yachts. He sells a low cost converter (discriminator) for your VHF radio. Roger Newby
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Old 27-09-2010, 11:40   #28
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I had a friend weld in one or two parts for my old sailor whf (parts cost 25 cents) about 4 years ago, it enabled audio modulation to the PC mic in.
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Old 27-09-2010, 12:01   #29
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I've just got a NASA 3 AIS engine + aerial for approx £130 including shipping for use on delivery trips, coupled with OpenCPN on a netbook with CM93 charts. OK, no transponder but at least I can see what is out there at a reasonable price.
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Old 27-09-2010, 14:14   #30
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Is this thread only to advertise this:

'cheapest AIS ...'

???

I am truly disappointed. Someone says it can be done then refuses to share the know-how.

Anybody?

barnie
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