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Old 30 December 2015, 08:05   #1
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Metz aerial..what height?

I am attaching the above aerial directly to the A frame which is approx 4 or 5 feet above sea level. I appreciate height is range. What height on an extension pole do you think I could get away with before it starts to look a bit "odd".Is it even worth extending it in the first case? Any smart ways of attaching it to the frame so it can be removed on car journeys? Nik
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Old 30 December 2015, 09:16   #2
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Quote:
Originally Posted by matata View Post
I am attaching the above aerial directly to the A frame which is approx 4 or 5 feet above sea level. I appreciate height is range. What height on an extension pole do you think I could get away with before it starts to look a bit "odd".Is it even worth extending it in the first case? Any smart ways of attaching it to the frame so it can be removed on car journeys? Nik
There's a formula kicking about somewhere which basically says that any height gained, exponentially increases the range, so on a RIB, you can't have too much height...in theory. In practical terms "generally" you don't need massive ship-ship comms range, any fellow cruisers will usually be within a mile or 2 of you, so won't be a problem. If you need to call the coast guard, his antenna is sat on top of a cliff on a ruddy great mast, so a couple of feet on your rib, ain't going to make a difference. As for removing for towing, a stainless steel ratchet mount is the way to go.
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Old 30 December 2015, 11:05   #3
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I had the same aerial on my last RIB in an attempt ton cure a fault, turned out it was the vhf but alas, I digress.

I mounted it ontop of the A frame and with a new vhf never had any concerns contacting anyone and it was certainly better than the rigid raider aerial it replaced.

I wouldn't go looking for problems, just fit it and I am sure it will be fine.
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Old 30 December 2015, 12:30   #4
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Quote:
Originally Posted by matata View Post
What height on an extension pole do you think I could get away with before it starts to look a bit "odd".Is it even worth extending it in the first case? Any smart ways of attaching it to the frame so it can be removed on car journeys? Nik
Surely the aesthetic depends on your boat, the design of a frame etc?

Sadly whilst height really does matter, it's not actually exponential - essentially it's proportional to the square root of the antanae height (Beware this is not the tip of the antenna). Moving from 2-3m in most circumstances doesn't give a great range enhancement. However the key thing to remember is vhf will not travel through waves. If you regularly go out in big waves height might help more than someone going far off shore in benign conditions. Similarly if you spend a lot of time with kayaks or dinghies using a handheld at just 0.5m above the water.
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Old 30 December 2015, 14:09   #5
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My Metz is mounted directly on top of a standard Ribeye a-frame.

Not had any issues and range is a well as can be expected.

Mind you- I don't do any of that Off-shore malarkey or 'big wave' shizzle.
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Old 30 December 2015, 16:48   #6
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Put my Metz onto a bespoke stainless steel light-pole which comes in three sections. The lightpole measures 54" high from the top of the transom to the light. The aerial is 36" high. From sea level to the tip is probably in the region of 7.5' high. On a good day I can even pick up Channel 4!
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Old 30 December 2015, 18:51   #7
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My Metz picks up Qhm and Yarmouth harbour from Southampton in my rib the antenna is hooked upto a Icom M323
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Old 31 December 2015, 04:33   #8
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Fit a folding stainless base, you can then just fold it down on car journeys, I don't know of any removable types.
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Old 31 December 2015, 08:45   #9
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I reckon the sea will become a ground plane and I've a recollection (somewhere deep in the grey matter) that 5ft above a ground plane is not a good height for an antenna. Some quirky thing. Probably more applicable to a horizontal antenna but just thought I'd drop that spanner into the works.
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Old 31 December 2015, 17:01   #10
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My Metz picks up Qhm and Yarmouth harbour from Southampton in my rib the antenna is hooked upto a Icom M323
Where is QHM's antenna? I'll bet its not on their roof.
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