Mobile Antenna

[tweiss3]

I'm a bit new to radio. I drive a lot, traveling with my company car. I've been using a CB with a magnetic LilWilly whip antenna. I also have to have access to the weather (outside of my phone) and always thought radio was cool, so I have a BF-F8HP that I have been using for analog scanning, which is a benefit because I get the county skywarn channels for weather alerts as well.

 

Anyways, I decided to grab a GMRS-V1 to be legal since I filed for my GMRS license. I have noticed, half the time if there is GMRS chatter, it is only picked up on the F8HP and not the GMSR-V1. Since I'm in a company vehicle, drilling is not an option. Should I go with a magnetic mounted antenna or just get a better 8" whip that is 1/4 wave. If i went magnetic, i'd get a triband that would have me ready for either a true 50W mobile rig or digital mobile scanner (P25 capable). If it helps, I currently clip the radio to my sun visor while scanning.

 

If magnetic, will there be a grounding plane required (similar to CB)? How large? Will it interfere with the CB?

 

If upgraded whip, any affordable optiosn other than Nagoya NA701C? 

 

I'm currently studying for my amateur technician test, but I still have so much theory I don't understand yet as far as antennas.

 

Thanks,

 

[kidphc]

Do not use the 3/4 traditional bit. It is probably for wood. It will walk and not produce a clean hole. Right tool for the job always. Btw, a professional will charge you about $200 for the job. Secondly, yes move the roof rack a bit. Any metal around the loading coil will mess up the pattern and cause other reception issues.

 

Best to drop the headliner at least in the area you will be working. That is the only way to confirm cross member supports interference issues. Measure 4 times then start. SLOW, SLOW this is not a race and patching up a hole on the roof ain't easy. The job is easy though. I do recommend a center punch so the bit doesn't walk till the circle part of the bit is at least partially bitten through. Then clean up the edges of inside of the circle with sand paper or a step bit (be careful this can bite to hard and cause a world of headaches).

 

Tape up the drill area with painter tape, Feel for the center punch mark and guide the tip to the punch. Then go slow. The tape minimizing chipping during the drilling process around the edge of the drill bit. Make sure the drill is perpendicular to the roof and not at any angles. You probably are going to want a use a step ladder to get above the work area without distorting the roof sheet metal.

 

There are two NMO size standard 3/4 and 5/8. I had a 3/4 NMO and 3/4 antenna. I ended up buying a Milwaukee 3/8 pilot bit and 3/4(19mm) hole saw. About $30 at HD. I don't really like the hole saw a lot. So I can't recommend it. 

 

After you drill put you figure through the hole and feel the edges, inside, top and bottom. Clean it up as much as you can if you feel a bur or draw blood. I put a dab of 100% silicone grease on o-rings. First to keep the o-rings from shifting as I tighten up things, Second to get a good seal. It's not necessary, especially if you clean up the area. Which you should do before you place the NMO in. Just a small flake of metal can shred the o-rings.

 

Have you ever thought about an NMO fold over antenna. They fold (manually) over so you can get clearance. In your case maybe enough to be hidden by the side roof rack bars and be save because of the height of the cross bars. Unless you have low profile cross bars.

[JJM]

Yeah don’t pay $200 dollars. Local installer charged me $20 the very first time I installed antennas. FOR THREE.

 

This is the hole saw I use

 

 

 

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[Lscott]

Think carefully about drilling a hole for an antenna mount. Most recent manufactured vehicles the sheet metal is rather thin. A through hole mount such as an NMO has a small diameter hole to support it. If the antenna gets whacked by a tree limb or from a low overhanging obstruction etc., the torque from the antenna exerted on the base and thus the surrounding sheet metal can be huge. There are stories where the mount ripped through the sheet metal or severely warped it. There has been damage reported just from the torque due to wind resistance driving at highway speeds when large really stiff antennas were used.

 

If you do drill a hole I would first research for a good way to reinforce the area around the mount location to eliminate damage to mount and or vehicle sheet metal from driving and minor antenna strikes.

[tweiss3]

No, the drill bit I'm talking about is a metal working drill bit, for my drill press, not to ever be used on wood. For just shy of $12, I will have that dewalt bit here tomorrow. I was more worried about not having it tomorrow/this weekend. Stores around here are a bit of a pain in the ass to get anything at.

 

Cross bars are 3-3.5" from top of roof to top of bars. Antenna is 6", so I'm not so much worried about overhead clearance. Antenna will stick up over crossbars, but will still be hidden.

 

I'm going to drill a 1/8" pilot hole after I use the punch. I will be slightly dropping the headliner, figuring out where the cross member is, then go slow. 

 

Wife gave the "ok" to install a radio in her car, as long as it looks good. She doesn't know yet I'm drilling the roof. She won't ever see it, so as long as the kids don't rat me out, she will never know.

 

The comet lip mount will be kept for "road trip CB" usage when I toss a CB in the car temporarily for vacation.

[axorlov]

Make sure you do not drill through the reinforcing beam under the roof sheet metal. Pull headliner a little or/and pull out the interior light that might be near the proposed spot to check for the right location for drilling.

[PRadio]

Honestly, the best thing to use for a hole in the roof is a knockout punch. https://www.amazon.com/Greenlee-730BB-3-Standard-Knockout-4-Inch/dp/B001UL13M2/ref=sr_1_8?dchild=1&keywords=knockout+punch+3%2F4&qid=1591377435&sr=8-8

[kidphc]

Honestly, the best thing to use for a hole in the roof is a knockout punch. https://www.amazon.com/Greenlee-730BB-3-Standard-Knockout-4-Inch/dp/B001UL13M2/ref=sr_1_8?dchild=1&keywords=knockout+punch+3%2F4&qid=1591377435&sr=8-8

Now I wish I had known about that.

[n4gix]

This is the proper tool for drilling NMO mounting holes. Note that it has a maximum depth of 1/8th inch, so there's no danger of damaging a headliner. There are other similar tools available some even lower priced, but this Larsen tool was the only one allowed in my GESS (General Electric Service Station) I once owned.


$49.95 at The Antenna Farm:
https://www.theantennafarm.com/catalog/laird-technologies-hs34-1647

[PRadio]

Knockout punches are the only thing I ever saw used by the companies I knew who installed police radios. The tool form the Antenna Farm looks nice but for the money, I'd rather buy the knockout punch. 

[JJM]

This is the proper tool for drilling NMO mounting holes. Note that it has a maximum depth of 1/8th inch, so there's no danger of damaging a headliner. There are other similar tools available some even lower priced, but this Larsen tool was the only one allowed in my GESS (General Electric Service Station) I once owned.

 

$49.95 at The Antenna Farm:

https://www.theantennafarm.com/catalog/laird-technologies-hs34-1647

The pilot bit looks longer than 1/8”

 

Also, the knockout looks like it still requires a hole to be drilled to be used. For that effort, I’d rather make the hole “once” from the outside vs having to go through the entire disassembly of the interior to drop the headliner enough for that knock-out too. That’s just me (and my previous 6 self-installed NMO mounts) talking.

 

Whatever OP feels comfortable with!

 

 

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[marcspaz]

Am I the only one who goes full-send with a diamond-edge titanium step bit, a 30 year-old Craftsman variable speed drill and some cutting oil?

[SteveC7010]

You have all cited some of the reasons that I now prefer 3/8” NMO’s. I can drill accurately from the outside with a drill stop on the drill bit so that the bit does even come close to touching the head liner. If the sheet metal is too thin, I can position a thin 3/8” fender washer on the inside to add strength and stability.

 

It’s increasingly rare that a headliner needs to be dropped. I just pull some the rubber seal around a door and there’s more than enough room to snake the coax to the B or C post. On most cars and trucks, I usually slip my hand between the headliner snd the roof.

 

Food for thought: On the Jeep Grand Cherokees and Dodge Durangos, the headliner is one piece. They install it through the front window opening long before they mount the front window. I am sure that other vehicles are built in a similar fashion these days. Dropping the headliner becomes less and less of an option.

 

Regardless of how one chooses to drill an antenna mount, It is imperative that coax (and any other upfitting wiring) not block an airbag. It is generally OK to slip your coax between the airbag and the body of the vehicle. Think twice; route once.

[JJM]

You have all cited some of the reasons that I now prefer 3/8” NMO’s. I can drill accurately from the outside with a drill stop on the drill bit so that the bit does even come close to touching the head liner. If the sheet metal is too thin, I can position a thin 3/8” fender washer on the inside to add strength and stability.

 

It’s increasingly rare that a headliner needs to be dropped. I just pull some the rubber seal around a door and there’s more than enough room to snake the coax to the B or C post. On most cars and trucks, I usually slip my hand between the headliner snd the roof.

 

Food for thought: On the Jeep Grand Cherokees and Dodge Durangos, the headliner is one piece. They install it through the front window opening long before they mount the front window. I am sure that other vehicles are built in a similar fashion these days. Dropping the headliner becomes less and less of an option.

 

Regardless of how one chooses to drill an antenna mount, It is imperative that coax (and any other upfitting wiring) not block an airbag. It is generally OK to slip your coax between the airbag and the body of the vehicle. Think twice; route once.

3/8” style require access from underneath to install, don’t they?

 

3/4” can be installed from on top/outside.

 

 

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[kidphc]

Am I the only one who goes full-send with a diamond-edge titanium step bit, a 30 year-old Craftsman variable speed drill and some cutting oil?

I would use one if I could find a good one for a price. Most places sell garbage step bits, you know chinese ones unless you spend some big bucks.

[marcspaz]

I would use one if I could find a good one for a price. Most places sell garbage step bits, you know chinese ones unless you spend some big bucks.

$150 for the one I have. You take them in to get them re-sharpened. The diamond belts are very cool... couldn't get a sharper edge if you tried. And it's fun to watch them do it.

[SteveC7010]

3/8” style require access from underneath to install, don’t they?

 

3/4” can be installed from on top/outside.

 

 

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Yes, but very easy to fish through from the inside. Certainly no more difficult than fishing the coax from the 3/4” hole towards its destination.

 

No matter which type you use, you still have to fish something from or to the mounting hole.

[JJM]

Yes, but very easy to fish through from the inside. Certainly no more difficult than fishing the coax from the 3/4” hole towards its destination.

 

No matter which type you use, you still have to fish something from or to the mounting hole.

I think getting the 3/8” mount up through the hole would be more difficult than pushing a 3/4” mount down into the hole. Idk

 

 

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[tweiss3]

Well, I just finished. Ended up cleaning the garage yesterday, and was too tired to attempt today.

 

I set the antenna 12" from edge of the back of the roof sheet metal. Routed the antenna cable down the D pillar, which keeps all the wire away from the airbags. Antenna is almost invisible, and I can still get drywall on the top. Also, I didn't have to move a roof rack bar.

Antenna Installed by tweiss3, on Flickr

Invisible Antenna by tweiss3, on Flickr

Antenna Location by tweiss3, on Flickr

Nobody is ever going to see or notice it. It fits right along the satnav receiver and the FM antenna.

 

I hid the receiver in the access panel where the jack is. Still have full access to the jack.

Radio Hiding Spot by tweiss3, on Flickr

Mounted Radio Hiding Spot by tweiss3, on Flickr

 

Routed the remote head wire up the D pillar and down the center of the roof, came out in the overhead shelf where it will be permanently mounted. Still waiting on the bracket, should be here Tuesday.

Remote Head Placement by tweiss3, on Flickr

 

Programmed it, and all works well. Wife is ok with it as long as it looks good. She recommended the head location. I like it because you can't see it though the window and won't give someone a reason to break in. Now to get her comfortable with using it.

[marcspaz]

Looks great!

[Lscott]

That does look like a neat install. How easy is it to get up on top to remove the antenna when necessary? I assume you have a cap to screw on the mounting base when the antenna is removed to keep out the elements.

[tweiss3]

That does look like a neat install. How easy is it to get up on top to remove the antenna when necessary? I assume you have a cap to screw on the mounting base when the antenna is removed to keep out the elements.

 

I don't have a cap yet, but i can reach it by standing on the rear bumper without an issue. I need to pick up a cap, it will probably be part of my next order.

 

My wife called on her way to work yesterday, first thing she said was "I can't even see the wires or anything." That's a good sign, she was worried it would be a half butt install. Talking to her this morning after I dropped the kids off, she mentioned that I have to show her how to work it, which means she is not opposed to learning. I'd say its a double win. 

 

Now I just have to find time to study for my technician exam, because I definitely want to get that taken and put behind me soon. I don't do well with tests.

[kidphc]

I don't have a cap yet, but i can reach it by standing on the rear bumper without an issue. I need to pick up a cap, it will probably be part of my next order.

 

My wife called on her way to work yesterday, first thing she said was "I can't even see the wires or anything." That's a good sign, she was worried it would be a half butt install. Talking to her this morning after I dropped the kids off, she mentioned that I have to show her how to work it, which means she is not opposed to learning. I'd say its a double win. 

 

Now I just have to find time to study for my technician exam, because I definitely want to get that taken and put behind me soon. I don't do well with tests.

Tech is super easy. Just study and take the practice exams. BTW, most just study for the general at the same time. Lots of cross over material. I wish I had done that.

[tweiss3]

Tech is super easy. Just study and take the practice exams. BTW, most just study for the general at the same time. Lots of cross over material. I wish I had done that.

 

I've taken about 6 online practice tests without studying and fall a few correct short from passing. 

 

Unfortunately there was a group testing this past Saturday that I didn't find out till Friday. I should have just gone and tested, but didn't feel like wasting $15. The even allow retests after everyone has gone, and up-testing. I need to keep an eye on the next available date. DMR is screaming my name, I'm a glutton for projects that can never be finished and always tweaked.

[kidphc]

You can do it. When you are scoring mid 90's on the test it is pretty much a pass at that point. Gl

 

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[tweiss3]

You can do it. When you are scoring mid 90's on the test it is pretty much a pass at that point. Gl

 

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I usually get 25 or so correct, when 26 is passing. I did just get 27, I should have gone Saturday, but I already had people lined up to help me clean the garage. Next testing date I'm going to just go.