Vhf aerial no A frame

[Red Fox]

Any idea for a vhf aerial for rib with no A frame?

[steco1958]

You will either have to use a transom mount, or if you have a console, attach to that.

[Nos4r2]

I'd put a pole mount on the transom

[office888]

Only if you limit power to 5 watts...

25 watts through most VHF antennas without an A-frame to add to the distance exceeds permissible radiation limits in most countries. Basically, you'll microwave yourself / passengers with the output.

However, yes, the idea of a tilting mount on the transom does work perfectly. Keep in mind that VHF is line-of-sight. Height is might.

[Red Fox]

Gulp... Microwave? If I wrap bacon round it then this could be a new way of cooking. So a mounting pole up to chest high then the aerial on that and all should be well? Looking at the cuddy fishing boats round here the aerials start at face height. No wonder their captains have that burnt face look.

[Nasher]

Have a search for old threads by Hightower, I'm sure he built a really nice folding pole for his antenna to mount on.

Nasher.

[Ovey]

At 25W the safe distance from the antenna is around 1m away. This is effectively a large baked bean can placed over the antenna with a 1m radius from the antenna.

Anything closer and you risk warming effects on the tissues of your body if you stand closer for any length of time. The long term effects haven't been fully determined yet. And this is non-ionising radiation (think water boiling), not ionising (think nuclear).

I create transmit system safe distance reports for a living after many years as a communications engineer in the navy!




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[willk]

Originally Posted by Red Fox

Gulp... Microwave? If I wrap bacon round it then this could be a new way of cooking. So a mounting pole up to chest high then the aerial on that and all should be well? Looking at the cuddy fishing boats round here the aerials start at face height. No wonder their captains have that burnt face look.

The world is full of wee boats with antennae mounted on handrails - they don't transmit much so I'd imagine those skippers are just embarrassed at getting spotted in cuddy boats

[Poly]

Originally Posted by Ovey

At 25W the safe distance from the antenna is around 1m away. This is effectively a large baked bean can placed over the antenna with a 1m radius from the antenna.

Anything closer and you risk warming effects on the tissues of your body if you stand closer for any length of time. The long term effects haven't been fully determined yet. And this is non-ionising radiation (think water boiling), not ionising (think nuclear).

I create transmit system safe distance reports for a living after many years as a communications engineer in the navy!




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Ah, now I understand Tara slightly more: http://i.dailymail.co.uk/i/pix/2013/...6_634x1112.jpg

I wonder if your 1m safe distance is based on dose and so has a temporal element?

[spartacus]

My bespoke stainless steel light pole and Metz antenna.

Hmmm, shiny!

[Ovey]

Originally Posted by Poly

Ah, now I understand Tara slightly more: http://i.dailymail.co.uk/i/pix/2013/...6_634x1112.jpg

I wonder if your 1m safe distance is based on dose and so has a temporal element?

With that smile I'd say Tara was sat on the antenna itself!


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[ShinyShoe]

Originally Posted by Ovey

At 25W the safe distance from the antenna is around 1m away. This is effectively a large baked bean can placed over the antenna with a 1m radius from the antenna.

Anything closer and you risk warming effects on the tissues of your body if you stand closer for any length of time. The long term effects haven't been fully determined yet. And this is non-ionising radiation (think water boiling), not ionising (think nuclear).

I create transmit system safe distance reports for a living after many years as a communications engineer in the navy!




Sent from my iPhone using RIB Net

Presumably there is an element of this that needs to consider the 'intermittency' (that should be a real word..) - there must be a difference from being 1m away from a 25W transmitter that is continually microwaving you from one that microwaves you only if you decide to talk?

I'm usually over 1m from the transom. I realise people have those sofa seats for the wife and kids at the back but I suspect most sofa seat ribbers will transmit twice a day for 15seconds at most... Wondering how that compares to say me walking about with my smart phone to my ear or tucked down my trousers while it merrily checks email, waits for SMS etc...

[Ovey]

Yeah, the safe distance only applies while transmitting. The 1m safe distance is a worst case, constant transmit scenario - not realistically going to happen. But still has to be taken into account by companies not wanting to fall foul of HSE and the EMF Directive.

As a private boat, it's up to you how to install an antenna. My advice is as high up as possible, which realistically is going to take it out of harms way anyway.

And mobile phones - are more dangerous, especially when long distances from the base station as they ramp up the power to "check in". Once again, it's not constant though.


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[willk]

Originally Posted by ShinyShoe

Wondering how that compares to say me walking about with my smart phone to my ear or tucked down my trousers while it merrily checks email, waits for SMS etc...

Or spending all day yapping into a 6w handheld in front of yer mush?

[popeyethesailor]

I made this pole up it also acts as part of my rod rest

[ShinyShoe]

Originally Posted by willk

Or spending all day yapping into a 6w handheld in front of yer mush?

But as you know I'm always very succinct and never yap, so you won't find me yapping on for ages and ages and ages into a handheld ;-)

[boristhebold]

Just get a folding Antanee mount and a extension pole mount, plenty available in chandlery stores. simples.

[Red Fox]

Originally Posted by spartacus

My bespoke stainless steel light pole and Metz antenna.

Hmmm, shiny!

Spartacus, Where did you get that made up. Looks good. How is it fixed to the boat at the other end? Thanks

[Last Tango]

More worrying would be the number of boats I see with radar mounted at eye level on the "A" frame or on a flybridge arch. Now that really will cook you !!

[treerat]

I bought a roof aerial pole from B&Q and used a pair of eye bolts to fix to the transom. Worked a treat.