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Raymarine forum - [TG11] Can I use GA150 GPS antenna with AIS700?

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Full Version: [TG11] Can I use GA150 GPS antenna with AIS700?
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I have 2 questions, but first a bit of context setting.
I purchased a GA150 GPS antenna along with lots of other Raymarine gear including an Axiom 12. Only then did I discover that the GA150 is not compatible with the Axiom 12 - apparently it only works with the Axiom 12 Pro.

Since I had already fitted the GA150 antenna to my davits and routed the cable through the length of the boat, I thought I would use it with the AIS700. I then hit another problem - it doesn't seem to work with the AIS 700 - I get an alert on my MFD saying the AIS has no position sensor fitted...or something like that. When I plug in the GPS antenna that came with the AIS, it works ok, however, it is just sitting loosely on the dashboard and is not permanently mounted.

So, my 2 questions are the following

1 - is the GA150 compatible with the AIS 700 as an external GPS antenna? They both seem to be passive GPS antennas, so why wouldn't they be interchangeable.

2 - If the answer is yes, the GA150 should work with the AIS700, then I suspect I have a broken GA150. What I have done is put a continuity meter across the external sheath and internal core and notice a difference between the 2 GPS antennas.
The one that came with the AIS reads approx 5Ohm, while the GA150 briefly reads something other than open circuit, but then quickly reads open circuit.
Is this normal, or is the unit defective?

Ideally, I'd like to use the GPS antenna mounted externally on my davits - its in a clear area and won't roll too much, so appreciate feedback on what might be happening here.

Hello Mike,

Sorry that you've not received a reply before.

The GA150 is different from the AIS700's antenna, and they are not tested or approved to be interchangeable. When I say approved, I mean in several ways - compliance with IMO AIS regulations (AIS GPS receivers are required to comply with the RAIM standard for integrity monitoring), marine EMC compatibility regs, and suitable performance and reliability for warranty purposes. Passive GNSS antennas come in 3V and 5V types, and I do not have any information on whether the AIS700 or GA150 are 3V, 5V or compatible with both supply levels. The AIS700 outputs a 3V level as do the displays that GA150 is compatible with but the AIS700's predecessor, AIS650, is 5V and it may be that the AIS700 antenna is dual-voltage capable but the GA150 is 3V-only. Frequency band is another area of possible incompatibility: the GA150 is a multi-band GPS+GLONASS antenna, whereas I suspect that the AIS700's may be GPS-only. I don't have the answers to these questions because this is not a connection that was ever intended to be made.

In short, as a manufacturer we can't approve using a non-compliant antenna with an AIS transceiver, and I think that there's a fair chance that they're not fully compatible because of the AIS's RAIM requirement and supply voltages.

To answer your other question though, the GA150 does show a 'capacitive' resistance that starts in the hundreds of kilo-ohms and rises as the cap charges when I measure one here. Your exact reading will depend on your meter, but yours doesn't sound abnormal.

Thanks Tom for your comprehensive answer. It makes good sense to me now.
You are welcome
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