The courage to start drilling......

[Matt C]

Well, the time has come to do my very fist every roof-mounted antenna, and to be honest I'm a little bit scared! My setup will be:

Sirio Super 9 'blue line' antenna (DV body-mount)
Thunderpole T2000 CB
A 57-plate, immaculate, low-mileage Suzuki Jimny!

So, I've bought a 12.5mm drill-bit especially for the job, will completely and carefully remove the headlining, and plan to mount as centrally in the roof as possible. Given how thin the roof sheet-metal is, I'm toying with cutting out the tin base of a biscuit-tin, drilling through the centre of it and sandwiching this also between the roof and mount to give extra thickness (it will, after all, be completely invisible when the headlining is refitted!)

For drilling itself, I'll put masking-tape on the roof to prevent scratches, use a centre-punch to get my mark, and will prop with wood underneath to reduce flexing, which I'll drill straight through and into, to hopefully get a tidier hole. I'll treat the hole with 'Kurust' prior to fitting, and use the opportunity of having all the B-pillar panels and sill-plates removed to give a good spray of 'Dinitrol' along any sill-joints....

So, for the experienced among you, I have the following questions:

1. Is there any merit in taking any paint off the inside of the roof metal, to ensure earthing-contact between the roof-metal and biscuit-tin metal, or will the fact that the mount is passing/clamping through both be enough?

2. When laying out the coax, should I remove any excess, or keep with the manufacturers length? (I would be careful not to coil the excess)

3. I intend to use a thin smear of silicone-sealant on the upper and lower sides of the rubber grommet, clamp in place whilst still wet, and immediately wipe-away the extrusion (again whilst wet). I toyed with the idea of using 'Sikaflex' rather than standard clear-sealant, or is this simply 'going overboard'?

Any other advice/suggestions gratefully received. I've been plucking up the courage to do this one, and keep telling myself that the benefits are that it will be the best performing and most robust install, and once done like this, I can swap between the 'Super 9' and 'Omega' by doing one DV wing-nut.

(Oh, and general observations are that I don't do 'green-laning'/off-road, don't have too much of a problem with low-branches, don't use multi-storey car-parks, and I live in the Scottish Highlands where we don't have motorways or high-speeds)

Thanks folks!

[Asterix]

Hi turtle
I will tell you of an experience I had with putting an antennas directly on the roof, I fitted mine about 8 inches away from the rear window centrally on the roof and it worked a treat, the only thing I found is that the wind resistance tends to drag the antenna backwards as your driving resulting in a very slight dip in the roof, I know you are fitting and bit of tin underneath the fittings which might be ok ( which I never did ) but maybe use something a little more stronger than thin tin and shaped to your roof line. Where mine was fitted Farley close to an edge I wouldn't of thought it would of made a dip but there you go. Just a little thought to consider maybe !!

[SuperMike]

On thin sheet metal, I would not use a drill, preferring a fine tooth hole saw, having first drilled a tiny pilot hole. Lots of revs at the drill and with only gentle pressure. Let the tool do the work, not you shoving.

[stampman]

guess its done now so if you give me your phone num then i can send any customers i get who want one fitting in the roof

[Dave 2000]

Yes a waaaay old thread but these thoughts may help someone considering this idea.

I would not use the extra biscuit tin ground plane/stiffener, you will get condensation trapped between the two, this results in rust/poor connection and the crap that goes with it when it bubbles through your outside paint. It really does depend where you live but I would not risk it.

What I would do if you must use the centre of a roof, is to scrap the paint to get your good earth/ground plane, and then fit a large 'penny' washer. Once all tightened up and coax connected and tight, spray the entire assembly with an anti rust paint, give it two or three light coats allowing each to dry.

regards

Dave

[Mr Benz]

Well, the time has come to do my very fist every roof-mounted antenna, and to be honest I'm a little bit scared! My setup will be:

Sirio Super 9 'blue line' antenna (DV body-mount)
Thunderpole T2000 CB
A 57-plate, immaculate, low-mileage Suzuki Jimny!

So, I've bought a 12.5mm drill-bit especially for the job, will completely and carefully remove the headlining, and plan to mount as centrally in the roof as possible. Given how thin the roof sheet-metal is, I'm toying with cutting out the tin base of a biscuit-tin, drilling through the centre of it and sandwiching this also between the roof and mount to give extra thickness (it will, after all, be completely invisible when the headlining is refitted!)

For drilling itself, I'll put masking-tape on the roof to prevent scratches, use a centre-punch to get my mark, and will prop with wood underneath to reduce flexing, which I'll drill straight through and into, to hopefully get a tidier hole. I'll treat the hole with 'Kurust' prior to fitting, and use the opportunity of having all the B-pillar panels and sill-plates removed to give a good spray of 'Dinitrol' along any sill-joints....

So, for the experienced among you, I have the following questions:

1. Is there any merit in taking any paint off the inside of the roof metal, to ensure earthing-contact between the roof-metal and biscuit-tin metal, or will the fact that the mount is passing/clamping through both be enough?

2. When laying out the coax, should I remove any excess, or keep with the manufacturers length? (I would be careful not to coil the excess)

3. I intend to use a thin smear of silicone-sealant on the upper and lower sides of the rubber grommet, clamp in place whilst still wet, and immediately wipe-away the extrusion (again whilst wet). I toyed with the idea of using 'Sikaflex' rather than standard clear-sealant, or is this simply 'going overboard'?

Any other advice/suggestions gratefully received. I've been plucking up the courage to do this one, and keep telling myself that the benefits are that it will be the best performing and most robust install, and once done like this, I can swap between the 'Super 9' and 'Omega' by doing one DV wing-nut.

(Oh, and general observations are that I don't do 'green-laning'/off-road, don't have too much of a problem with low-branches, don't use multi-storey car-parks, and I live in the Scottish Highlands where we don't have motorways or high-speeds)

Thanks folks!

I drilled a hole in the roof of my then two years old Mercedes W124 estate to fit a K40 mount at the rear , and another centre front , above the interior light to fit a roof mounted FM aerial for the diversity tuner in my Sony head unit ( which needed two antennae , there was already the one in the rear wing ) . I'm now on my 5th W124 estate and I always just leave the redundant roof mounts in the cars if i sell them on , but usually I give them away with half a million miles on them as by then they're worth next to nothing . I normally put some gaffer tape on the roof to prevent swarf marking the paintwork near the hole and start by drilling a small pilot hole and then either work up to the required size , or use a suitable hole saw to cut a larger hole ( K40 mount needs a fairly large hole , from memory something around 20 mm give or take , while since I did it ) . Go carefully , it isn't that scary .

[Ossie12pints]

Hi, I've recently mounted a mini orbitor for a friend and told him from experience that if he wants it on a body mount the antenna will need to be cut shorter. Sure enough I drilled the hole and mounted the antenna and ended up cutting 3cm off to get a good swr. I've now done 3 of these on a fixed body mount with the same results. The orbitor seems to be ok on a mag mount but too long when body mounted with a really good ground. Just saying

[Smithdoor]

FYI
It best to drill or cut on the ridge .
If can I use vent for cable.

My background is metal buildings and people will cut holes any where and then have leak.
That why say only at the rigde very little water will leak in and may not be noticed.
Down eve you have a lot of water flowing in .
⸻⸻ In wall ⸻⸻
If drill in wall drill angle so water flows out of your home. It only needs to just few degrees to make a difference.
I found a lot of buildings where guy drill hole from outside and ange so water comes in to building and seal fail a years later.

I hope this helps installers

Dave