Reply
 
Thread Tools Search this Thread
 
Old 11 January 2010, 20:29   #1
Member
 
Country: UK - England
Town: North East
Boat name: Sarah Louise
Make: Honwave T38IE
Length: 3m +
Engine: 15 Yamaha, 8 Mariner
Join Date: Jul 2008
Posts: 228
Vhf antenna length/make?

Hi guys,
I've trawled through past posts but can'tfind one that addresses my question.
I am after an antenna for my 4.6m boat, but cannot decide which length/ make to go for.
I will be using the boat within 10 miles of the shore and already have a handheld radio, so am installing this for better range. However I don't want too long a length for transporting.
The pacific ones on ebay look good (Cheap ), what do you guys think?
Cheers,
Geoff
__________________
Fishery Pokery is offline   Reply With Quote
Old 11 January 2010, 20:56   #2
Member
 
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,299
Are you mounting it directly onto the transom?
__________________
Downhilldai is offline   Reply With Quote
Old 11 January 2010, 21:07   #3
Member
 
Channel Ribs's Avatar
 
Country: UK - Channel Islands
Town: Alderney
Length: no boat
Join Date: Sep 2006
Posts: 3,047
Quote:
Originally Posted by Geoff_Jubb View Post
The pacific ones on ebay look good (Cheap ), what do you guys think?
Pacific antennae are anything but cheap, third best on the market perhaps. Very highly recommended from me at least.

Size really comes into its own for receiving, as a minimum option the 0.3m helical antenna that Pacific do is very good, the Seamaster Pro version even better.

Mounting height is perhaps more important than length.
__________________
Channel Ribs is offline   Reply With Quote
Old 11 January 2010, 21:16   #4
Member
 
Country: UK - England
Town: North East
Boat name: Sarah Louise
Make: Honwave T38IE
Length: 3m +
Engine: 15 Yamaha, 8 Mariner
Join Date: Jul 2008
Posts: 228
I am thinking of mounting it on the transom, or some kind of instrument mount/console thingy I have yet to concieve. Either way, it will be about transom hieght.
With the pacific antennas, the ones I am looking at seem to start at £25. Is this the same make that you talk of?
Thanks for your help,
Geoff
__________________
Fishery Pokery is offline   Reply With Quote
Old 11 January 2010, 21:22   #5
Member
 
Channel Ribs's Avatar
 
Country: UK - Channel Islands
Town: Alderney
Length: no boat
Join Date: Sep 2006
Posts: 3,047
Quote:
Originally Posted by Geoff_Jubb View Post
With the pacific antennas, the ones I am looking at seem to start at £25. Is this the same make that you talk of?
Yes, should be. Mounting low can be a problem, not least of which you have quite a bit of power radiating out when you transmit.
__________________
Channel Ribs is offline   Reply With Quote
Old 11 January 2010, 21:30   #6
Member
 
Country: UK - England
Town: North East
Boat name: Sarah Louise
Make: Honwave T38IE
Length: 3m +
Engine: 15 Yamaha, 8 Mariner
Join Date: Jul 2008
Posts: 228
Is thr radiated power dangerous?
Does anyone have any ideas for mounting an antenna without an A frame, as mine is a SIB for fishing and I would prefer not to go down that route if possible?
Cheers again for your advice,
Geoff
__________________
Fishery Pokery is offline   Reply With Quote
Old 11 January 2010, 21:38   #7
Member
 
Channel Ribs's Avatar
 
Country: UK - Channel Islands
Town: Alderney
Length: no boat
Join Date: Sep 2006
Posts: 3,047
Quote:
Originally Posted by Geoff_Jubb View Post
Is thr radiated power dangerous?
Given the small amount you will probably use it to transmit, no. But it is something to think about.

Using a small pole with the antenna on top would be good.
__________________
Channel Ribs is offline   Reply With Quote
Old 11 January 2010, 23:48   #8
Member
 
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,299
As it's going to be sitting at transom height, I'd suggest you go for a 1.5m antenna on a fold down base and fix it on the inside face of the transom.
A pole would be a good solution. You could make the pole removable, if it helps with storage.
__________________
Downhilldai is offline   Reply With Quote
Old 12 January 2010, 13:36   #9
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,667
I had a removable pole on my old boat. Easy to either hinge at the bottom so it folds onto the floor or pull out with an inline waterproof connector.

The main issue I could see with transom height is you will make a very good absorber for the outgoing signal, esp. if you are on 1W ......

Height (above water level!) is good!
__________________
9D280 is offline   Reply With Quote
Old 12 January 2010, 13:44   #10
Member
 
Channel Ribs's Avatar
 
Country: UK - Channel Islands
Town: Alderney
Length: no boat
Join Date: Sep 2006
Posts: 3,047
Pacific do a mount for their Pro range that sits inside 1" tube, the antenna itself is then removable to you do not need an inline connector so long as you are happy with whatever length of tube you go for.

This is the 1m version of the Seamaster Pro...

http://www.pacificaerials.co.nz/Mari...ssAntenna.aspx

The antenna, cable, pole and tube fitting should come to less than 30 quid.
__________________
Channel Ribs is offline   Reply With Quote
Old 13 January 2010, 19:08   #11
Member
 
Country: UK - Wales
Town: Llanfair pg
Boat name: just about to change
Make: Aircraft
Length: 8m +
Engine: Outboard
MMSI: 13
Join Date: Jul 2008
Posts: 221
Just a quickie
For info only
VHF works by line of sight

So if boat 1 has a 10ft high spike
And boat 2 has the same

Theoreticlly each will 'see' each other for 4 miles
Therefore they can communicate if they are 8 miles apart.

I,m sure you all wished to know that

OK
I,ll feck off and go and watch the footy Then
__________________
www.seawake.co.uk
kawasaki is offline   Reply With Quote
Old 13 January 2010, 19:22   #12
RIBnet admin team
 
Poly's Avatar
 
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: Tohatsu 30HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 11,622
Quote:
Originally Posted by kawasaki View Post
So if boat 1 has a 10ft high spike
is that measured from the base of the antanae or the top? makes a big difference on a small rib/sib especially with no a-frame
__________________
Poly is offline   Reply With Quote
Old 13 January 2010, 20:39   #13
Member
 
Country: UK - England
Town: North East
Boat name: Sarah Louise
Make: Honwave T38IE
Length: 3m +
Engine: 15 Yamaha, 8 Mariner
Join Date: Jul 2008
Posts: 228
Quote:
Originally Posted by 9D280 View Post
The main issue I could see with transom height is you will make a very good absorber for the outgoing signal, esp. if you are on 1W ......
And I haven't even got a profile picture... ;D
__________________
Fishery Pokery is offline   Reply With Quote
Old 13 January 2010, 20:44   #14
Member
 
Country: UK - England
Town: North East
Boat name: Sarah Louise
Make: Honwave T38IE
Length: 3m +
Engine: 15 Yamaha, 8 Mariner
Join Date: Jul 2008
Posts: 228
I think I will go with what you describe Malthouse, but there is a small chance I will build some kind of DIY A frame.
Does your shop stock the things you mention?

Thanks everyone for your help,
Geoff
__________________
Fishery Pokery is offline   Reply With Quote
Old 13 January 2010, 21:03   #15
Member
 
Country: UK - England
Town: Warwickshire
Boat name: True Blue
Make: Humber ocean pro 6.3
Length: 6m +
Engine: Mercury 150 opti
Join Date: Oct 2005
Posts: 456
This probably won't be relevant to you Geoff but one thing that we find is that a large proportion of ariels are supplied with a five meter cable and we would advise avoiding any joins or extension cables where possible so may be worth checking that the aerial that you are looking at will have a long enough cable with it
__________________
Ian Sharlot is offline   Reply With Quote
Old 14 January 2010, 06:11   #16
Member
 
Country: UK - Wales
Town: Llanfair pg
Boat name: just about to change
Make: Aircraft
Length: 8m +
Engine: Outboard
MMSI: 13
Join Date: Jul 2008
Posts: 221
Quote:
Originally Posted by Polwart View Post
is that measured from the base of the antanae or the top? makes a big difference on a small rib/sib especially with no a-frame
The theory is, 10ft above sea level.

So in realty it is just a fairly accurate guidline.

Yachts for instance.
Will enjoy better ship to ship communication with their 'spikes' mounted on top of a tall mast.

30ft (above sea level)for those chaps would give them about 8 miles each.
Therefore a 16 mile 'range'

Then again weather conditions, the sea bobbing us up and down etc will affect reception etc.

Basically, the higher the better really though.

Obviously HM Coastgaurd has antennas dotted about the place.
Which is why sometimes you may hear the CG transmitting when you are 20 miles from Him
But you wont hear the vessel responding.

For instance
I like to stick me radio on Ch 84 Holyheads CG's Ch for 'routine traffic' normally and stick the 'dual watch' facility on.

So 16, cos everything starts there, or should!
Plus on 84 I can hear the CG and sometimes the vessel responding.

Just kinda makes me feel safe, to know who is about and whats going on.
Plus I,m a nosey git
__________________
www.seawake.co.uk
kawasaki is offline   Reply With Quote
Old 14 January 2010, 07:29   #17
RIBnet admin team
 
Poly's Avatar
 
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: Tohatsu 30HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 11,622
Quote:
Originally Posted by kawasaki View Post
The theory is, 10ft above sea level.

So in realty it is just a fairly accurate guidline.

Yachts for instance.
Will enjoy better ship to ship communication with their 'spikes' mounted on top of a tall mast.

30ft (above sea level)for those chaps would give them about 8 miles each.
Therefore a 16 mile 'range'

Then again weather conditions, the sea bobbing us up and down etc will affect reception etc.

Basically, the higher the better really though.

Obviously HM Coastgaurd has antennas dotted about the place.
Which is why sometimes you may hear the CG transmitting when you are 20 miles from Him
But you wont hear the vessel responding.

For instance
I like to stick me radio on Ch 84 Holyheads CG's Ch for 'routine traffic' normally and stick the 'dual watch' facility on.

So 16, cos everything starts there, or should!
Plus on 84 I can hear the CG and sometimes the vessel responding.

Just kinda makes me feel safe, to know who is about and whats going on.
Plus I,m a nosey git
I know that - I am familiar with the numbers which have all been posted here in the past. But you didn't actually answer the question - can I expect to be able to talk to an identically rigged boat from at 8 miles if I have a a 10ft long aerial mounted at the top of the transom or only if it is in fact 10 ft above the gunwale?
__________________
Poly is offline   Reply With Quote
Old 14 January 2010, 08:07   #18
Member
 
Country: UK - Wales
Town: Llanfair pg
Boat name: just about to change
Make: Aircraft
Length: 8m +
Engine: Outboard
MMSI: 13
Join Date: Jul 2008
Posts: 221
Quote:
Originally Posted by kawasaki View Post
The theory is, 10ft above sea level.

So in realty it is just a fairly accurate guidline.


I don't think it would make a great deal of diffence if it was mounted on the transom or the gunwhale.

Higher the better obviously.

Just trying to point out the type of range we can expect rib to rib.

VHF as we know is 'line of sight' .

But as others have posted.
There are other things to consider.

Tother thing
Like land in the way
Sometimes I have locked into Port Dinorwic marina.
The Dockmaster has an ariel on His office roof.
Dunno
Could be 40ft up.
Until I clear a headland approaching from the North its about a mile away until He hears me
Tother way I can raise Him from about 3 miles away
The spike on me little mobo is about 10ft above sea level.
Figures I gave are probaly 'in the best possible scenario'

Just as a guidline.
__________________
www.seawake.co.uk
kawasaki is offline   Reply With Quote
Old 14 January 2010, 08:12   #19
RIBnet admin team
 
Poly's Avatar
 
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: Tohatsu 30HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 11,622
Quote:
Originally Posted by kawasaki View Post
I don't think it would make a great deal of diffence if it was mounted on the transom or the gunwhale.

Higher the better obviously.
I think your misunderstanding me. I'll post a piccy later.
__________________
Poly is offline   Reply With Quote
Old 14 January 2010, 08:35   #20
Member
 
Channel Ribs's Avatar
 
Country: UK - Channel Islands
Town: Alderney
Length: no boat
Join Date: Sep 2006
Posts: 3,047
Quote:
Originally Posted by Polwart View Post
is that measured from the base of the antanae or the top? makes a big difference on a small rib/sib especially with no a-frame
I tend to measure effective heights of antennae from two thirds up the active length.

There is a proper rule, I will see if I can dig it out.
__________________
Channel Ribs is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




All times are GMT. The time now is 07:45.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.