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Old 04 October 2015, 07:30   #1
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Fixed VHF on a sib

Just bought a DSC Standard Horizon VHF radio.
Milling over how to affix it to my Honwave 3.5ae.
Decided that I'm going to screw the set to the underside of the seat inside the under seat bag.
Aerial states the tip should be at least 5m from the ground.
The aerial itself is only 1.6m.
The transom is approx 50cm.
I would need to another 3m according to the instructions to gain best performance.
I doubt it will exceed 3m when I attach it.
Anyone got experience of VHF performance when aerial set at around 3m?
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Old 04 October 2015, 09:37   #2
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3m will still be floppy! Plenty of RIBs have A frame <2m from sea level with a 70cm ant on it..

The higher the better. Life is full if compromise...
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Old 04 October 2015, 12:56   #3
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True what the instructions say but you can only mount to its highest place on the boat my last rib was set on the AFrame at 2m antenna 500mm pretty much the norm whip action will be a problem too high now I own a SIB I am going hand held D.S.C backed up with PLB I would mount as you said on the seat or transom and see how you go. You could buy a telescopic window cleaning pole for an emergency situation if height is what you desire or army surplus may have something you could adapt.

Cheers
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Old 05 October 2015, 11:58   #4
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5m? I suspect that most RIB's won't meet that.

Mine is mounted mid-way up the arch, so an 8 ft antenna about 4 or 4.5' off the water.

As said above, the higher the better, but on most boats, you can only do so much.

jky
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Old 05 October 2015, 13:50   #5
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I'd aim for getting the base up above seated head height - so you don't cop too much RF.
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Old 06 October 2015, 10:57   #6
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Quote:
Originally Posted by willk View Post
I'd aim for getting the base up above seated head height - so you don't cop too much RF.
Importance of that depends on how chatty you are. If you're like me, you don't send all that much radio traffic; IMO not a really big deal. You probably get substantially more exposure from day to day use of a cell phone (which I also don't use as much as some...)

OTOH, I haven't really researched the effects of VHF band waves on the human body. Anyone know of a quick and dirty rundown?

jky
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Old 06 October 2015, 11:32   #7
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Cheers guys for the replies.
I don't tend to be too chatty at all.
I have a 6w Standard Horizon handheld which clips to my person at all times.
The fixed set was just go give a bit more range should the sh@t hit the fan.
I have been a bit more adventurous in my Sib the last two years doing a bit of island hopping and camping around the West coast of Scotland mostly on my own.
I intend to use the set to pass my intentions on to the C.G and shout up when i arrive etc.
Other than that it will be for emergency use only.
The aerial itself is just over 5 ft tall.
I'm going to mount it just above the top of the transom.
Combined height of 7 ft ish.
I'll be around 1.5m from the aerial.
Hope I don't fry my already scattered brain
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Old 07 October 2015, 13:34   #8
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Had a faff around with the VHF aerial today.
Cut some metal to make a mounting bracket.
I've decided to bolt it onto my auxiliary engine outrigger.
See pic attached.
I'm going to make another bolt in section to add more height if required.
Since taking the photo it's been cut to shape and painted.

On another note anyone know anything about GPS antennas.
Instructions with VHF state it requires a NMEA cable and antenna to get GPS coordinates.
What's the cheapest way of rigging one up?????:what:
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Old 07 October 2015, 14:07   #9
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If you have a chart plotter /GPS connect the two together with the NMEA cable Kaman shows position on vhf then mate
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Old 07 October 2015, 14:27   #10
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Fixed VHF on a sib

This should do it
http://www.yachtingsoftware.com/ever...FUe3GwodVvEHnw

Or this
http://www.force4.co.uk/veethree-gps...Q#.VhVlw1V4XCQ
.....sh1t happens.......
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