Suggest me a small boat aerial solution

[Poly]

OK - so I finally got round to getting a fixed VHF radio for my wee (3.9m) boat when a bargain popped up here this week.

I'm now going to need an aerial. My limited knowledge tells me (i) height will be the most important thing (ii) a high gain is OK on a powerboat. (iii) IIRC it would be better to raise the base of the aerial rather than just use a taller one?

I don't have (and am not going to add) an a-frame. I have a small (50cm?) removable light pole for my all round white light which is mounted on top of the console. Console is quite cluttered already though.

So what nice solutions have the small rib/sib people come up with for fixed VHF antennae. What's the preferred aerial? Is something like the Metz a good solution? How do people mount it?

Bear in mind that I am true to all stereotypes of Scotsmen and therefore mean and hamfisted!

[SPR]

baseball cap with Velcro on top and Velcro on base of antenna ! long cable ish stand up for better reception... sorted

S.


www.firstaidatsea.co.uk
www.SPRmarine.co.uk

[willk]

Originally Posted by SPR

baseball cap with Velcro on top and Velcro on base of antenna ! long cable ish stand up for better reception... sorted

If the cap fits...!

[SPR]

add antenna to poormans gecko ....



ideal solution poly !

[Poly]

Thanks guys ;-)

It seems Andy beat you to it though: http://cdn.rib.net/forum/attachment....2&d=1321661565

[SPR]

lol - you did say you were tight!

S.


www.firstaidatsea.co.uk
www.SPRmarine.co.uk

[SPR]

i would consider - using a s/s core fibre glass antenna bolted to transom. maybe with extension pole.

do the maths and make the choice is the extra metre "worth" it....

VHF Transmitting and receiving distances

The distance to the horizon in miles is 2.2 times the square root of the height of antenna in metres. For example an antenna on top of a 9m mast would have arrange to the horizon of...

2.2 x square route of 9 = 2.2 x 3 = 6.6 miles

If the shore antenna was 100m high then...

2.2 x square route of 100 = 2.2 x 10 = 22 miles

Total range would be 6.6 + 22 = 28.6 miles.

In practice the radio horizon is slightly more than the visible horizon - so add say 10% - 28.6 + 2.9 = 31.5 miles (i.e. between 30 to 35 miles)

[whisper]

As you say go high! A cool ss fat light pole with a massive VHF arial on top would be just the job

[Peter_C]

Where are you going to mount your VHF?

I run a 5225XT Shakespeare antenna, mounted to the transom. Works pretty good in my small boat. There is a mount that can fold it right into the boat so it is safe.
5225-XT | Shakespeare Electronic Products Group
Style 4187-HD | Shakespeare Electronic Products Group

You can see part of the antenna on the port side.


Folded into boat. (Your boat might be a little short for an 8' antenna, so take measurements.)

[jyasaki]

I think you need to get *something* mounted, rather than worry too much about optimum performance. VHF doesn't have a really great range in any case (line of sight for the most part), so getting the radiating element another foot or two higher isn't going to gain all that much.

I understand the whole higher is better thing, but having an OK performing VHF is better than having one sitting in the garage for trying to figure out where to put it.

jky

[Poly]

Originally Posted by Peter_C

Where are you going to mount your VHF?

I have a console so its going somewhere there. I've not been down to the boat since it arrived to work out where.


jky - fair points. I have a handheld that I currently use, and given the recent change in the weather I think there will be plenty of time for playing with mounting ideas before I play with the boat again anyway. Heightwise - does the base really want to be above any wave/swell height we expect?

SPR's maths show communicating to a good mast high on land is "easy" but I guess I'd also like to be in range of WAFI's who might be the only people around, I've no idea how many CG masts are in the right place, at the right height.

[whisper]

Here's a small boat aerial

[Ovey]

You could always look at the V-tronix RIB antenna and mount it on a pole (think broom handle). Then you could fix two U brackets on the transom (or side of the console) that the pole slides into, making it removable for transport or storage.


Sent from my iPhone using RIB Net

[9D280]

On my old SR4 I used a bit of "tough" (i,.e underground type waste pipe. I then used a blanking cap drilled for the base. I then fitted two stainless pipe holders to the transom to hold it up.

I lived with a loop of cable so I could pull it out for travel / garage door avoidance. I sold the boat not long after, so never got round to fitting the Bulgin Buccaneer to the bottom of the pole which would mate with one on a bracket and then screw in to hold the mast in. I taped some thin rope (3mm or so plait) above the top bracket and lashed it down to the bracket to stop it falling out (vibration lifting it) while I sourced the Buccaneer. - that survived two trips and someone made me an offer for the huill I couldn't refuse so can't tell you how the "Buccaneer mount" plan would have worked.....

[jyasaki]

Originally Posted by Poly

Heightwise - does the base really want to be above any wave/swell height we expect?

Base doesn't matter; it's the radiating portion that needs to be up. In glass antennas (Shakespeare, etc) there is an array of elements normally about a foot and half long (rough guess) that sits about 1 to 2 feet from the tip of the antenna. Don't know much about the base-loaded designs, but I assume the wire aerial part is actually doing the radiating, so again, base wouldn't matter (assuming I'm correct about how they work.)

jky

[Hightower]

Originally Posted by Poly

Thanks guys ;-)

It seems Andy beat you to it though: http://cdn.rib.net/forum/attachment....2&d=1321661565

Where ever did you trawl that one up from?

[Poly]

Originally Posted by Hightower

Where ever did you trawl that one up from?

:-) I was searching for solutions following SPRs helpful answer and stumbled across it!

[Hightower]

Originally Posted by Poly

:-) I was searching for solutions following SPRs helpful answer and stumbled across it!

My son isn't thanking you for that!

[Peter_C]

This link has some good info regarding antenna design. Anatomy of a Shakespeare Galaxy antenna

Originally Posted by Ovey

You could always look at the V-tronix RIB antenna and mount it on a pole (think broom handle). Then you could fix two U brackets on the transom (or side of the console) that the pole slides into, making it removable for transport or storage.

A fishing pole mount works awesome! My boat came with two of them and I repurposed the starboard side one to hold my aluminum dive flag pole (Shown in my first photo above, and made from free recycled material ), plus I have an all around white navigation light pole that slides in the bracket.

[spartacus]

+1 for a multi-piece collapsible stainless steel 316 light pole and Metz antenna!