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Discussion Starter · #1 ·
Hi

Can anyone tell me which roof aerials fit a pop top? According to 'Dabonwheels' the Kinetic and Hirscmann aerials only tolerate a max panel thickness of 2.5mm whereas my pop top is 12mm thick. Any help most welcome ☺.

Regards

Rob
 

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Hi

Can anyone tell me which roof aerials fit a pop top? According to 'Dabonwheels' the Kinetic and Hirscmann aerials only tolerate a max panel thickness of 2.5mm whereas my pop top is 12mm thick. Any help most welcome ☺.

Regards

Rob
We got the Kinetic from dabnonwheels. I drilled a 50mm hole with a holesaw through the fibreglass and then mounted a one foot square metal plate to act as the earth, and also bolt the aerial. Apparently they work better with a large metal base, here is a pic of the finished article, also got the Necvox for the tv from them and installed that permanently to the front to save dragging the wire through the window each time.....and when the roof is popped it is much higher so improves reception.

 

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As an ex-Royal Signals Microwave Radio Tech, (and prior to that AM CB'er) the correct terminology for the "Earth" that cocoa refers to in his post is actually called a "Ground Plane" *see http://en.wikipedia.org/wiki/Ground_plane for the theory).


But basically you need metal for the radio waves to "reflect" off the metal plate to hit the antenna, to assist the radio in getting as strong as signal as possible - this is one reason that VW's concept of placing the aerials in the glass windscreen and the wing mirrors of latter models is seriously flawed and reception is not the best, oh and add in the fact that the vans body acts as a bloody great Faraday Cage (look it up) to block the radio waves, then that's why so many people complain about poor reception.

Also if you could find a way of connecting the plate bonded to the fibreglass pop top to the body of the van (or any metal of the van that is electrical at battery earth) then this would also assist the efficiency of the ground plane as it would give it greater electromagnetic mass (for want of better words).
 

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Discussion Starter · #4 ·
Thanks chaps, its obviously not as straightforward as I thought :-(. I have ribs on my roof so it's not that easy to fit a plate. Strange though that some of the Kinetic glass mounted aerials produce "near perfect reception' according to 'Dabsonwheels'.

Has anyone else had success fitting a roof aerial to a pop top without fitting a reflector plate?

Thanks in advance.

Rob
 

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You dont have to have a reflector "plate" in the sense that it has to be rigid, but basically anything that has a thin sheet of metal on/in it.

So you could use a 1 ft square piece self adhesive sound deading mat like Dynamat whcih has a thin sheet of metal on one side and can be shaped around contors.

The other thing is it doesnt even need to be a square or circle, it can be 25mm wide 12" strips coming off at the four points of the compass, which will give a ground plane "effect" electrically (there are then called "radiators"). And again they could be made of Dynamat etc.

Also be wary of others who say they have fiited an antenna to their fibre glass pop tops and have encountred no issues as many factors come into play i.e. where do they use the van is it locally within good range of one of the national radio transmitter side (in the RF shadow basically).

The boating fraternity often have the same challenge on fibreglass boats so something like this http://www.tunetrapper.com/Hidden_Car_Antennas.html ( $58/£38 including shipping to Europe) which is a 1/2 dipole solution maybe worth considering but at least it doesnt require a ground plane as its alreday built in to the design.
 

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Discussion Starter · #6 ·
Fascinating stuff Glitch!

Just a thought , could the reflector plate be on the inside i.e. under the fibreglass roof?

Rob
 

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Fascinating stuff Glitch!

Just a thought , could the reflector plate be on the inside i.e. under the fibreglass roof?

Rob
100% yes as long as the antenna passes through it and is electrically i.e. bolted/touching it then that's no problem at all.
 

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Discussion Starter · #8 ·
Super, that's the way to go then. I see that the reflector plate should ideally be at least 3m / 4 ie 75cm across.

Being a natural sceptic I'll try the aerial both with and without a reflector plate :).

Cheers.
 
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