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Old 01 April 2008, 07:38   #11
Country: USA
Town: Negaunee, Michigan
Make: Avon SR6
Length: 6m +
Engine: 150hp Evinrude
Join Date: Oct 2007
Posts: 63

Spoke with a fabricator today.

I will be going with a single post with steps. Suitable for a white light on top and a step (braket) to mount an antenna.

I agree with the comment of having my brain fried by radio waves.

The post will only be tall enough for the light to clear our heads. He was worried about vibrations on too long of a post causing stress on the transom. He explained that the longer the post the more wiggle like a tuning fork an could make the effects of a sudden slap of a wave last much longer through transferance.

Makes sense to me.


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Old 01 April 2008, 08:46   #12
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,538

Yes, a longer pole will "whip" slightly more if you slam a wave, but vibration wise you may find that a longer pole helps - remember the most likely constant vibration will be from your engine - a longer pole will have a lower natural frequency, so is less likely to "sing in tune" with it.......

Bigger diameter will be stiffer and not hugely more heavy.

How are you planning on fixing it on? Could you get the fabricator to make an over length version, and if you're clever with a couple of temporary clamps (e.g. u- bolts at the same spacing as your fixing plates), do a trial run, check it for resonsance, can then cut it down a bit if it sings, and when you're happy, weld on the "proper" mount brackets? Remember three mount points will help a LOT to stiffen it up.

For what it;s worth my prototype SR antenna mast (holding up a Vtronix Raider) was made form a length of 40mm exterior grade black plastic waste pipe form the local plumber's merchant! It survived half a season with no misdemeanours. (then I sold the boat).

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Old 01 April 2008, 13:19   #13
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Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,829
So what diameter tube is it made from?

Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
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Old 01 April 2008, 15:55   #14
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,298
Originally Posted by Pete7 View Post
Ah yes the Fareham design ...
I hope you Fareham boys aren't claiming rights to the original Llanelli design

Some pics which may help TB Minnow when specifying bracketry etc. Originally, it only had the VHF antenna bracket, then I added the GPS antenna by simply using a flat plate sandwiched between the VHF antenna and its mounting plate
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Old 17 May 2008, 18:41   #15
Country: UK - Scotland
Town: Inverness
Boat name: none
Make: none
Length: 5m +
Engine: none
MMSI: none
Join Date: Mar 2007
Posts: 1,908
I have designed my pole to be a T shape, it means the VHF and GPS have clear fields of view rather than being mounted lower with some shading caused by the pole itself. The disadvantage is the anchor light is slightly shaded by the aerials from the side. Will post a pic when it arrives from the fabricators.
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Old 18 May 2008, 02:02   #16
Country: UK - England
Town: ramsgate
Boat name: Micki Dee Bee
Make: Ribcraft Seasafari
Length: 9m +
Engine: Twin 250hp Suzuki
MMSI: 235057235
Join Date: Jan 2004
Posts: 1,622
Send a message via MSN to Jon Brooks
Don't panic!!

Originally Posted by 9D280 View Post

I know you are talking about antenna on the console, but do you really want 25W of RF power blasting through your brain at such point blank range? Also if it's on the console, a good chunk of it's "view" will be obscured by you & your passengers, reducing its effectiveness. Putting it on a pole will also give it a few more feet altitude, giving much better range.

Ok before we all go running for the hills and stop using our radio's lets add some perspective here.

UHF and Cell Phones are far far more dangerous than marine VHF and to the best of my knowledge there are no reported case of anyone getting fried whilst using their marine radio. Also if you look at how often you actually transmit the danger is, if at all, very small.

As mentioned by getting the VHF antenna up on a frame or on pole it will increase your range But consol mounted antenna's do work well.

There seems to be some train of thought that you need to get the GPS antenna up high to, this is not the case. Many, me incluled, have the GPS antenna consol mounted and it works fine. There is no proof that they work better higher up so save yourself cable run and agro and flush mount on the consol.

IMHO an A Frame even on a smaller boat is a god send ans it gives you more place to stow bit in polly bottles etc. If they are frame mounted this then frees up the deck space etc.

Hope that helps.
Jon Brooks VSMM. Marine Mammal Medic, PBI, SRC Assessor,PWC Instructor.
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Old 18 May 2008, 05:36   #17
Country: UK - Scotland
Town: Inverness
Boat name: none
Make: none
Length: 5m +
Engine: none
MMSI: none
Join Date: Mar 2007
Posts: 1,908
As long as the GPS has a clear field of view and is horizontal it should work just as well mounted low as high.
Unfortunately my console has only one place I could do this and it isn't ideal for several reasons.
Since the boat NMEA network needs to go back the outboard anyway it is only a few feet further to put it on the pole beside it.
I didn't go for an A frame this time for reasons of cost and usability. It was far too expensive to buy or have one made and I had loads of space for storage anyway. It also helps access to the aux which was always a bit of squeeze on the old boat.
The only thing I am missing I would have likd is a bit radar reflector and I would have needed a large double tubed frame to carry it at a cost of around 700 more than my pole is costing!

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