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Author Topic: took the plunge and punched the roof  (Read 4175 times)
K7RBW
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« on: March 18, 2012, 08:46:35 PM »

In a testament to nothing being as easy as you'd like or as hard as you thought, I finally punched a hole in the roof of my 2010 RAV4. Things I needed to avoid: the moonroof, and the airbags. The moonroof was much less of a problem than I expected because the NMO mount doesn't need much room below the roof line. But, it turns out there's an airbag that runs above the front door and the back door (from the A pillar to the C-pillar). So, I wasn't going to be able to just fish the coax down the pillar like I'd hoped.

Instead, I removed the interior trim panels and dropped the headliner to see what was going on. It turns out the moonroof has a 1/2" plastic drain tube that runs behind the airbag so I ran the coax along the drain tube.

Punching the hole...it wasn't too scary.

I bought the 3/4" NMO hole saw to cut the hole. Measured about 20 times to make sure it was centered, clear of the moonroof, etc. triple-checked everything, I drilled a small pilot hole and then cut the 3/4" hole. The hole saw makes a very clean hole with very little burring. I sanded the hole anyway and set the mount. I ohmed-out the cable before buttoning everything back up.

Over all, it wasn't too big of a deal (once I got over the fact I was cutting a big hole in the roof). Best part of the whole thing is that it looks very clean and better than some of the alternatives to punching a hole. I know everyone says that this will lower the resale value, but I don't believe it. If you do it wrong, sure, but done right, it looks like it came that way from the factory.
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KC7YRA
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« Reply #1 on: March 18, 2012, 09:57:43 PM »

Congrats!!!  Fine feeling isn't it.

I have punched thousands of holes for NMO mounts and it just gets easier.  Every time I go buy a new vehicle, it gets at least 3 NMO mounts put in that same day. 

I don't buy vehicles for resale, I buy them to work.  And a good NMO mounts works great.  No cables in the door jambs. No unsightly wires to get caught on boots or tools.  And the performance is tops.

You won't regret it.

Brad
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K5LXP
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« Reply #2 on: March 19, 2012, 06:12:23 AM »

Did you keep the 3/4"  "washer" as a souvenir? 


Mark K5LXP
Albuquerque, NM
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K7RBW
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« Reply #3 on: March 19, 2012, 06:25:33 AM »

Did you keep the 3/4"  "washer" as a souvenir? 


Mark K5LXP
Albuquerque, NM


I wanted to, but I'm not sure where I put it, now. I did take it out of the headliner, though.
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N5VTU
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« Reply #4 on: March 19, 2012, 07:27:26 AM »

"I wanted to, but I'm not sure where I put it, now. I did take it out of the headliner, though."

Look to see if it's still inside the hole saw.

Punching that hole in the roof didn't hurt a bit, did it? Wink
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K5LXP
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« Reply #5 on: March 19, 2012, 10:13:23 AM »

I wanted to, but I'm not sure where I put it, now.

Put it on your callsign badge for all to see at the next hamfest.  A mark of distinction...


Mark K5LXP
Albuquerque, NM
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N6AJR
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« Reply #6 on: March 19, 2012, 10:31:02 AM »

I recently did the same thing to my pickup.  Actually a friend of mine did the work as I am disabled, but we put 4 nmo mounts on the roof of the cab, and took out the center part of the little "jump seat" in the middle front to get access for a home brew "tower" for 5 radios.  900/2m/220/1.2g/ HF.  works well too.  I also have a 800 watt power inverter mounted on the floor of the passenger side to plug in the laptop, drill or coffee pot while parked mobile..  I have a couple more antennas on the bed rails.  great fun.

One other alternative on a car is to go to the junk yard and get an extra rear  trunk lid for your car.  put this one on the car and drill away.  when selling the car, put the original one on again.
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KK4IKO
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« Reply #7 on: March 20, 2012, 03:30:21 AM »

OK guys and gals, a  newbie here...taking Technician next month.

I have a regular Jeep Cherokee Sport (2000).  My OEM roof rack has a metal cross bar about 3" above the roof, but I'm not sure if there is a metal connection between the crossbar and the roof track.

I've almost resigned myself to punching the roof, but am wondering if a roof rack mount that close to the roof and centered, will have an adequate ground plane. 

Also, give me some opinions on tri-band mobile antennas...I would like to run 2 and 6 meters, or is this wishful thinking?

Bruce

 
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AC4RD
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« Reply #8 on: March 20, 2012, 04:14:41 AM »

Iput 4 nmo mounts on the roof of the cab, and took out the center part of the little "jump seat" in the middle front to get access for a home brew "tower" for 5 radios. 

Have you sent K0BG any photos for his website?  That installation sure sounds like it would be interesting to see!
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K5LXP
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« Reply #9 on: March 20, 2012, 06:48:14 AM »

You probably should've started a new thread.

My OEM roof rack has a metal cross bar about 3" above the roof, but I'm not sure if there is a metal connection between the crossbar and the roof track.[

Even if it did, it'd be ~2 feet from where the antenna mount is, unless you mounted the antennas right at the ends of the rack.

Quote
I've almost resigned myself to punching the roof, but am wondering if a roof rack mount that close to the roof and centered, will have an adequate ground plane. 

If the rack is metal it will act as radials, and in close proximity to the plane of the roof you will get some benefit from that too.  The question comes down to if you're willing to accept whatever you get in terms of pattern and match.  It won't be "as good".  Only you know what degree of performance you expect.  By poking the hole, you know for sure it's as good as it can possibly be.  On the rack, you get what you get.


Quote
Also, give me some opinions on tri-band mobile antennas...I would like to run 2 and 6 meters, or is this wishful thinking?

You didn't say what the third band was.  10M?  440?  220?  Depending on what the other band(s) are and your performance expectations will dictate which antennas(s) you will ultimately end up with.  I'm guessing you're looking at the all-in-wonder whips from china or whatever, and about all I'd offer on that is they'll present a load, and they'll radiate something.  You don't hear many happy stories about how durable or efficient they are.


Mark K5LXP
Albuquerque, NM

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K3GM
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« Reply #10 on: March 20, 2012, 08:27:28 AM »

..........Also, give me some opinions on tri-band mobile antennas...I would like to run 2 and 6 meters, or is this wishful thinking?

Before you punch the hole in your roof with plans for a tri-band antenna, look at the available options out there at the moment.  Assuming you're looking at 6m/2m/70cm, there isn't much.  The available model(s?) uses a stiff spring steel lower section that I would not recommend placing on a vehicle roof.  It will not yield to overhead branches which would tear the mount from the roof, damaging the sheet metal.  I have one of these sitting unused for that very reason.  Quite a few years ago, Diamond made an SG-M911 that used small diameter sections.  I have one of these and it has lasted many years, but has stated to show its age.  It's very "whippy" and yields very easy to branches.  I had intentions of replacing it until I saw the potential for severe sheet metal damage the new one presented.   My recommendations would be to install two NMO mounts, and install a Larsen NMO-2/70 on one, and a Larsen 6m coil and whip on the other with a diplexer at the radio.  This is what I've done, and it works very nicely.
« Last Edit: March 20, 2012, 08:29:11 AM by K3GM » Logged
KK4IKO
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« Reply #11 on: March 20, 2012, 11:22:31 AM »

K5LXP and K3GM,
 Thanks for the help, you've confirmed my suspicions.  I was thinking 6 and 2 meters, plus 70cm for the three band, although I'm told that there's not much activity on 70 in this area.  Two antennas, haven't thought about that.
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K7RBW
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« Reply #12 on: March 21, 2012, 06:46:30 AM »

One thing I've noticed about my new roof mount is how flimsy the sheet metal is up there. I put the mount in the flat spot between the stiffening ribs in the roof, giving it about 6" of flat, un-reinforced sheet metal between the ribs and nothing ahead or behind it. (it looks pretty good Smiley )

When I put a tall, stiff, and rather heavy antenna on the mount and moved it back and forth (as the wind might do while driving), I saw how it flexed the roof's sheet metal. This caused me to wonder what would happen if I accidentally drove into a garage or drive-thru with a stiff (no-spring) antenna. I'm guessing that it would be bad news for both the antenna and the roof.

For now, I have a stubby, 12" antenna up there, so I don't have to worry. But, I don't think I want to drive with anything longer that isn't spring loaded.
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M6GOM
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« Reply #13 on: March 21, 2012, 07:41:38 AM »

One thing I've noticed about my new roof mount is how flimsy the sheet metal is up there.

Seems to be the way. My friend has a Vauxhall Astra van. His is a 2005 model and he can mount antennas in the roof with no issue. Someone at a hamfest had the 2006 model of his van which looks exactly the same. The guy said he had to put strengthening plates on the underside of the roof as it was thinner.
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KK4IKO
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« Reply #14 on: March 21, 2012, 07:44:36 PM »

K3GM...If one installed two antennas, my IC706MKIIG radio has two connections, one for VHF/UHF, and one for HF, how far apart do the antennas need to be?  Also, is the skinny teflon coax worthwhile, it would be a lot easier to snake two of them down inside the door post and under the floor molding.

Bruce
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