K40 Antenna on a VW Jetta Wagon Mounting without drilling.

[romad275]

I'm trying to figure out the best way to do this on my 2005 Jetta Wagon. When the hatch opens, the top front edge rotates down below the top plus there isn't enough room for the edge mount anyway. I could use the magnet mount but they scratch the paint. Has anyone done this either to a similar wagon hatch?

Two possibilities are using my hitch mount or attaching a large ferrous plate to the underside of the bumper cover with a ground strap to a ground point on the car underbody.

 

[mmckenna]

As I'm sure you know, the "best" way to do it is to actually drill the hole. Anything else is going to be some level of compromise.

Center of roof with permanent mount is best.
Mag mount center of roof is next in line.

Mounting it low off the trailer hitch is going to put a lot of the antenna below the vehicle (unless you are running a 102" whip) and the lopsided ground plane is going to make the radiation pattern skewed off the back of the vehicle.

If the first two options are totally out of the question, then your best shot is to mount off a fender bracket in the hood channel. Use an NMO mount base with something like a Larsen NMO-27.

If that's out….
A lip mount bracket off the side of the hatch might be a good choice, but it's difficult to get a good ground connection that way.
Something like this might work:

Diamond® Antenna ~ K412CNMO Trunk Lip Mount

But expect paint damage. Also, like any non-permanent mount, you are going to need to be very careful with the coaxial cable. It'll get pinched and chafed where it goes through the hatch, and that can let water in.

 

[JoshuaHufford]

Probably the most common used words on this site, and good reason for it.

Just drill the hole, you will be glad you did.

 

[mrweather]

All due respect, it's a 15 year-old car. Drill a hole. Indeed, the larger roof of a station wagon will offer a nice groundplane for the antenna.

 

[mmckenna]

Yeah, what they said ^^^^.

Seriously, drill the hole.
It will NOT reduce resale value, no matter what anyone tells you. I've traded in a lot of vehicles over the years/decades with NMO mounts on the roof, and they JUST. DON'T. CARE. Car dealers usually auction the cars off to brokers, and they pretty much do it sight unseen and don't care about an antenna mount. If it became an issue with a private sale, stick a cell phone antenna on it and tell them it's for boosting the cell signal. Then charge them extra for it.

I understand the desire to not pop a hole in a perfectly good car, but it's really not an issue if it's done correctly. And it does improve performance, especially on the lower frequencies.
It also looks better than hammy/hobby grade compromise mounting gadgets.

 

[romad275]

Thanks for the suggestions, however the hole drilling was DOA (my bad as I should have specified it was a non-starter). On my 1990 Miata I have a tuned splitter that allows me to use the stainless steel antenna mast, but that isn't an option as the Jetta has a shark fin antenna. None of the hatch clamp type will work due to the lack of clearance between them and the body (if there was room I'd use that type of mount as it is what came standard on my K40).

As for possible leaks caused by the coax entering via the hatch opening, I always route wires and cables so a drip loop is created BELOW the lowest opening of the hatch/trunk - never a leak in over 40 years!

 

[mmckenna]

Thanks for the suggestions, however the hole drilling was DOA (my bad as I should have specified it was a non-starter). On my 1990 Miata I have a tuned splitter that allows me to use the stainless steel antenna mast, but that isn't an option as the Jetta has a shark fin antenna. None of the hatch clamp type will work due to the lack of clearance between them and the body (if there was room I'd use that type of mount as it is what came standard on my K40).

Well, doesn't leave you a whole lot of options. You are going to need to get creative.

I've got a friend that wanted to run an HF rig in a Mini Cooper. He removed the shark fin AM/FM/Satellite antenna and fabricated at mount that would allow a screwdriver antenna to be placed in the hole. Looked goofy as hell, sort of like a bumper car with the tall antenna sticking up, but it worked well.

Glass mount antennas don't work worth crap, unless you only need a very short range.

Usually when I get in that sort of situation, I take a trip to the hardware store and just wander the isles until I get an idea. Usually you can find a bracket or mount that will do something.

As for possible leaks caused by the coax entering via the hatch opening, I always route wires and cables so a drip loop is created BELOW the lowest opening of the hatch/trunk - never a leak in over 40 years!

Yeah, that's a good plan.
However, water intrusion into the inside of the car isn't the only issue. Depending on how you have it routed, the coaxial cable can get pinched, which changes it's characteristic impedance. Probably not enough to make a difference to a CB radio, but something to consider. Pinch it enough, and you can damage the cable enough to get a short between the center conductor and shield. Damage the jacket, and water can get into the cable and corrode the copper.
But careful inspection and routing can address that. Whatever works best for you is the right choice.

Let us know what you figure out. It's going to be a challenge, but not impossible.

 

[romad275]

I think for now I'll just do the following:

1. Clean area of roof where I'll put the antenna
2. Heavily wax area
3. Place a 6"x6" minimum microfiber cloth on waxed area
4. Put the 5" diameter K40 magnet base on the cloth and route cable
5. Attach K40 antenna

The Mini Cooper idea is good except I need the satellite radio antenna for my SiriusXM radio. I figure CB transmissions won't cause a problem with the satellite radio reception since the latter's downlink frequencies are centered about 2.34 GHz (2,340 MHz) vs CB's 27.185 MHz (.027185 GHz).

 

[mmckenna]

I think for now I'll just do the following:

1. Clean area of roof where I'll put the antenna
2. Heavily wax area
3. Place a 6"x6" minimum microfiber cloth on waxed area
4. Put the 5" diameter K40 magnet base on the cloth and route cable
5. Attach K40 antenna

The Mini Cooper idea is good except I need the satellite radio antenna for my SiriusXM radio. I figure CB transmissions won't cause a problem with the satellite radio reception since the latter's downlink frequencies are centered about 2.34 GHz (2,340 MHz) vs CB's 27.185 MHz (.027185 GHz).

That's probably your safest approach. I think the microfiber cloth will be an issue, though. It's going to absorb moisture and dust and may cause more issues than it'll prevent. You might be better off with a layer of clear packing tape stuck to the roof of the car where the magnet will sit. Many many years ago I used a mag mount on a truck and was concerned about the paint. I used a piece of cut bumper sticker to put down and the magnet on top of that. Worked well enough.

CB won't impact the satellite radio, you should be OK.

 

[romad275]

That's probably your safest approach. I think the microfiber cloth will be an issue, though. It's going to absorb moisture and dust and may cause more issues than it'll prevent. You might be better off with a layer of clear packing tape stuck to the roof of the car where the magnet will sit. Many many years ago I used a mag mount on a truck and was concerned about the paint. I used a piece of cut bumper sticker to put down and the magnet on top of that. Worked well enough.

I figure the microfiber cloth can be washed an dried between uses since the antenna doesn't have to be on the car all the time. Your packing tape suggestion also has me thinking about getting something like XPEL paint protection applied to a small area of the roof, probably the right rear corner.

 

[mmckenna]

I figure the microfiber cloth can be washed an dried between uses since the antenna doesn't have to be on the car all the time. Your packing tape suggestion also has me thinking about getting something like XPEL paint protection applied to a small area of the roof, probably the right rear corner.

If the cloth is thin enough, it'll probably work fine. But too much space between the bottom of the antenna and the roof top will impact the inductive coupling to the ground plane that is needed for the antenna to work correctly.

 

[romad275]

The cloth is 17 mils or 0.432mm

 

[mmckenna]

The cloth is 17 mils or 0.432mm

Give it a try. Check your SWR afterwards to be sure.

 

[romad275]

IF I can find my SWR meter! I may have to get another one. Are the old analog models still good enough or should I look at getting a digital one?

 

[mmckenna]

IF I can find my SWR meter! I may have to get another one. Are the old analog models still good enough or should I look at getting a digital one?

I prefer analog ones. Easier to see intermittent issues. And they work fine. While it's probably well outside your budget, the Bird 43 is still the industry standard for watt meters. Mine is probably 50 years old.

 

[romad275]

Dang! I remember using one of those when I was in ground radio maintenance in the Air Force 1969 - 1974 before I was assigned to TACP duty.

 

[mmckenna]

Dang! I remember using one of those when I was in ground radio maintenance in the Air Force 1969 - 1974 before I was assigned to TACP duty.

Yeah, they are so stinkin' simple, not much to go wrong with them. I bought mine used since there really isn't anything that can wrong with them.

 

[JoshuaHufford]

If your car has roof racks, I suggest wrapping the coax around one of the racks to keep the coax up off the paint, the coax slapping against the paint while your doing highway speed can do some damage. I do that on my Subaru when I use a mag mount on it. I'm on a waiting list to get a NMO drilled and put in the center of the roof, but it has been put off further from current conditions.

I'm planning on removing the shark fin antenna as I don't use sat radio and putting in a second NMO mount there. I was going to have the installer do it all at one time but now that it may be a while I might tackle that one myself.

 

[romad275]

Yes, I have racks but I'm planning to put the antenna at the right rear corner of the roof, just in front of the hatch. There I should only have maybe 3 - 4 inches of cable between the magnet base and the hatch opening. The problem may be clearance for the cable between the hatch edge and the roof. I just dug out the antenna from storage for a test fitting tomorrow. If I end up having to go though the right rear pax door then I will have to do something to prevent cable slap, especially since the K40 antenna base only has a 3-foot RG-58A/U cable that ends with Mini Male UHF connector. The main cable has a Mini Female UHF connector on one end and a PL-259 on the other.

 

[romad275]

IF I can find my SWR meter!

Found it! It is a Mura CBM-20 SWR/Power/FS Meter that I've had for 30 - 40 years.