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Old 22-03-2014, 12:36   #1
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what's this thing on my mast?

I'm trying to figure out how much of the stuff the PO installed on this boat to keep. We've gotten rid of a lot, already, since many of our priorities are obviously different.

I'm about to climb up the mast for the first time and replace the totally destroyed VHF antenna that lightning hit. I've been puzzling over this other antenna, not sure what it is. WiFI? Television?

I figure this will be familiar to some of you, which saves me from climbing up just to read the label to decide whether I want to keep it. What's gotten my attention is the coaxial cable already run to it. I am wondering if I could get rid of this thing and use the cable and mount for a steel VHF whip.
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Old 22-03-2014, 15:25   #2
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Re: what's this thing on my mast?

No ideas I guess. Must mean it's obsolete and I can junk it.
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Old 22-03-2014, 15:31   #3
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Re: what's this thing on my mast?

Looks like WiFi to me, but I'm far from an expert

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Old 22-03-2014, 16:00   #4
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Re: what's this thing on my mast?

Navtex missing the whip? Where does it terminate in the boat?

As for the coax, it would depend on what type it is to know if it is suitable for a vhf. It looks rather small from the pictures. What type is it?

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Old 22-03-2014, 16:16   #5
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Re: what's this thing on my mast?

Looks like an old Magnavox Transit Satnav antenna.
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Old 22-03-2014, 16:30   #6
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Re: what's this thing on my mast?

How long is that? It looks like a NAVTEX antenna, those are usually quite short (less than a foot), but I can't tell the size from the picture.
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Old 22-03-2014, 17:32   #7
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Re: what's this thing on my mast?

How old is your boat/mast?

I had a Loran (or was it Decca) ariel that looked very similiar on a boat many, many, many moons ago.
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Old 22-03-2014, 17:34   #8
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Re: what's this thing on my mast?

Looks like an internet booster antenna. I have one similar to hoist in a marina or anchorage for hotter connections. It will pick up un-protected WI-FI at a couple miles.

Fine the end in the boat. Is it USB?
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Old 22-03-2014, 17:42   #9
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Re: what's this thing on my mast?

The WiFi boosters usually use either USB or CAT-5 cable (I have a Bullet with Ethernet and POE) but this looks like round coaxial cable from the pictures. That would indicate a VHF or perhaps a TV antenna (do you have some unidentified hardware aboard labeled "Glomex"?).
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Old 22-03-2014, 17:46   #10
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Re: what's this thing on my mast?

Forget reusing the coax no matter what the type is. You have been struck by lightning and the existing coax is very old. Both of those are reasons to replace it.

It is certainly not a USB cable at the top of a mast. Not even an active one.

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Old 23-03-2014, 07:00   #11
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Re: what's this thing on my mast?

Thanks for the ideas. I have no clue what it is. The boat is 30 years old and we're the fourth owners, so it could have been on there since 1985, or 2012 when we bought it. I was SO hoping someone on the forum would just say something like, "oh yeah, I recognize that, it's the Motorola Super Scat Grabber Model 3 and it will help you....." blah blah.

Or even better "Hot damn! I'll give you five hundred bucks for that and pay the shipping..."

But it looks like I am going to have to finally drag my fat, lazy, crippled old carcass up that mast and take a look.

Oh, the co-ax is still a bit of a mystery, too. In that telephoto photo, it sure looks to me like maybe heavy cable with something like an Amphenol or similar on it. But the cable is dark. I have looked around in the bulkhead connectors I can access below the mast, and the only un-attached/un-identified one is a skinny white coax with a BNC style twist on connector. I don't know the number, off hand, but would guess that it's that white RG-58/U stuff that comes in packaged coils at Radio Shack (Tandy).

So now I am asking myself is that a coax cable from an antenna up there, or a multiconductor cable that is going somewhere I haven't found yet? Or ( even worse) did a previous owner splice a piece of RG-58 to something, somewhere?

I'm still dragging my feet hoping someone will recognize that antenna. I asked two cruisers at the marina yesterday, and neither one recognized it. Both their boats are less than ten years old, too.
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Old 23-03-2014, 11:21   #12
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Re: what's this thing on my mast?

Definitely a Magnavox SatNav antenna.
I used to have one of those back in the mid '80's.
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Old 23-03-2014, 14:59   #13
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Re: what's this thing on my mast?

Quote:
Originally Posted by senormechanico View Post
Definitely a Magnavox SatNav antenna.
I used to have one of those back in the mid '80's.

The antenna belongs to the Magnavox MX4102 - they were very popular back in the day. I only pulled mine out a couple of years ago. Nice bit of kit. You could go for 90 mins or so in between fixes and you could input your speed/heading manually for it to maintain a DR fix until it next updated. Mine was interfaced with the B&G to get around that, and was fairly standard on racing yachts at the time. It was realativley common to have the antenna mounted inside the boat (for example mine was to be found tucked up out of the way in the stern locker).

Almost military like in its robustness (used to use a bigger brother to this one on destroyers actually), it also had some nice features in that the back lighting would gradually turn on/off as the system knowing your position and the time, knew sunset/sunrise times.

Even up uniil I took it out, it powered up just fine (no sat fixes obviously) and would happily calculate DR positions once initialized.

Only use for it now is the dumpster or leave it as a talking point...
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Old 23-03-2014, 15:28   #14
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Re: what's this thing on my mast?

Thank you very much. I looked at various old systems on the internet trying to spot it, but haven't yet found a photo for a positive ID. The satnav motorola antenna images I found were like little dish antenna. This Looks omnidirectional in the horizontal plane, but not that great for lookig straight up. I'm wondering if it could have been an early GPS integrated into a satnav or something like that.

I've already thrown away a few things from the boat and then found out later that I might have eventually found a use for them. I wanted to be sure that this was, indeed, something useless before removing it entirely. Much appreciated.
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