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Old 04-06-2017, 15:00   #1
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External Antenna Needed for VHF GPS?

Looking at purchasing an Icom M324G VHF fixed mount radio, which has built in GPS. Will I be able to acquire a good signal if I mount it below deck in my Tayana 37 or do I need to connect it to an external antenna?
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Old 04-06-2017, 15:09   #2
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Re: External Antenna Needed for VHF GPS?

Do you have a small handheld GPS, like a Garmin? If so, try it in the same position and see how well it does.
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Old 05-06-2017, 07:45   #3
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Re: External Antenna Needed for VHF GPS?

Freelandken,
Paul made a good suggestion!
And, this is what I would do, too!

In case you don't have a handheld GPS lying around (some smartphones / tablets have GPS built-in, as well), the short answer for you is:
You will most probably have no issues getting and holding a GPS fix with the radio mounted below decks on a Tayana 37 (fiberglass hull and decks)...

FYI, here is a pic showing part of my Nav Station, where a Garmin GPS76 is mounted...this supplies dedicated GPS position data to both of my DSC radios (Icom M-602 VHF-DSC-FM and Icom M-802 MF/HF-DSC-SSB)....it works great (and while I upgraded the Garmin to a slightly newer model, using the older one in my dinghy, it's worked great like this for almost 13 years now!)



fair winds..

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Old 05-06-2017, 08:01   #4
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Re: External Antenna Needed for VHF GPS?

My Standard Horizon VHF radio with built-in GPS (AIS) is located below decks and has always been able to acquire a GPS signal. My boat is very similar to your Tayana.
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Old 05-06-2017, 08:21   #5
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Re: External Antenna Needed for VHF GPS?

You will be able to see ships on the AIS from further away if you can get that antenna higher. If you sail offshore the extra notice would be very valuable.
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Old 05-06-2017, 09:12   #6
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Re: External Antenna Needed for VHF GPS?

phoenix,
Freelandken is referring to his GPS reception of the built-in GPS receiver (in the Icom M324G)...
Quote:
Originally Posted by phoenix-marie View Post
You will be able to see ships on the AIS from further away if you can get that antenna higher. If you sail offshore the extra notice would be very valuable.
But, I like your sense-of-humor!

Fair winds....

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Old 05-06-2017, 10:33   #7
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Re: External Antenna Needed for VHF GPS?

Our Vesper GPS came with an external GPS antenna but it worked so well using the internal one that I never wired it up. It's mounted below on a fibreglass boat.
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Old 05-06-2017, 12:01   #8
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Re: External Antenna Needed for VHF GPS?

I have some gear with an external antenna at the nav station, right next to an iPad, using its internal antenna. I don't usually notice any difference.
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Old 05-06-2017, 18:27   #9
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Wink Re: External Antenna Needed for VHF GPS?

GPS can be received below decks in a fiberglass boat. In the radio world, higher is always better in most all cases. As for VHF marine radio transmitting in particular, having an antenna in your face, located next to your other electronics etc., is a very bad call. If you exclusively talk VHF in the harbor only on very low power, well, fine. But at 35, 50 or higher wattage, seriously consider an antenna located well above all persons on board. (Be sure to select a VHF antenna sold as not requiring a ground plane.) The comment about AIS, that is all about VHF Channels 87 & 88 digital data, not GPS. So having your antenna higher off the water results in significantly better AIS coverage, let alone increased distance of Channel 09 & 16 calls, along with better GPS updates too!!! Fair Winds to all.....
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