I have installed mobile HF and VHF rigs in several TDI's we have owned, starting with a 2000 Jetta sedan 5-speed and later a 2001 Beetle automatic, a 2006 Jetta sedan automatic and currently a 2009 Jetta sedan 6-speed. All had factory sunroofs except the 2009.
An IC-706 Mark II G was the HF rig (used in all but the Beetle).
The control head was mounted in the dash area with the body of the transceiver in the trunk, typically with the bracket bolted up under the rear window shelf. In the 2000, there was a storage spot in the dash that I removed and used to mount the control head. A VHF FM rig also would fit in that space.
In the Beetle, a Yaesu FT1500m 2-meter rig fit in nicely in the cubby just forward of the gearshift, under the dash. For the no-holes mount, I cut a piece of wood to snugly fit into the cup holder there, and the rig's mounting bracket was screwed into this wood.
In the 2006 and 2009 (A5 models), the IC-706 control head was mounted in the cubby just forward of the gearshift, under the dash -- on a small panel that was strapped to the two "handholds" on either side. There's enough room under the control head to slip in a Vibroplex Junior paddle for mobile CW (morse code).
A separate VHF FM radio was mounted on its side on the passenger side of the center console, with multiple wire ties holding it to the center console "handhold." There was still enough room to open the glove box, and my wife (AB1P) hasn't complained on the intrusion into the passenger knee space.
I ran power directly from the battery, with a fuse in the positive line there. In the 2000, I used a piece of RG8 and ran it under the body and up through an existing grommet into the bottom of the trunk. In the others a 2-conductor wire came through the firewall, either slipping through with an existing wire bundle or in the case of the automatics, through an existing grommet used to plug the unused clutch opening. The wire then was snaked along the center hump, with a junction block near the gearshift to tap in for the VHF rig, and the power cable continuing to the trunk, under the rear seat, for the IC-706.
For antennas, an MFJ dual-band quarter-wave magnet mount sufficed for VHF on the middle of the roof, with the wire snaked in along the pillar of the passenger side rear door. Run the RG58 coax all the way down to the bottom of the door edge before bringing it into the cabin to avoid water entry along it.
On the 2000, I installed an NMO mount in the small roof space between the windshield and front of the sunroof. I got access through the ceiling control area just forward of the sunroof. I used either a 5/8 wave whip for 2 meters or a quarter-wave, the latter to avoid hitting the ceiling in low-clearance parking garages.
On the 2006 and 2009, I installed a second 2-meter quarter-wave on a gutter clip on the trunk. There wasn't enough clearance to mount it on the top, so it went on the rear (vertical surface). I then bent the antenna element just above the mount to form a right-angle so the antenna was vertical. With one cheapie antenna it would not stay vertical until I added some glue, but others did just fine without any, so YMMV.
I have seen others mount VHF antenna NMO mounts directly on the top of the trunk, removing the inside insulation for access.
For HF, I mounted either a simple single-band Pro-Am (Hamstick style) helical whip or a KJ7U screwdriver (160-6 meters) off the rear of the car. In the 2000 and 2006 I used the tow ring to mount a piece of galvanized angle iron or U-channel that stuck out below and beyond the bumper just enough to mount the antenna. This will affect clearance slightly on certain driveway or garage entrances (similar to how a hitch will).
On the 2009 I mounted a trailer hitch and the screwdriver support steel was attached to this in the area of the tow ring.
The HF antenna feedline came into the bottom of the trunk through an existing rubber plug on the passenger side. I just punched a hole in the center of it large enough to accommodate the coax.
The 2000 had the lowest noise floor on HF of any of the cars. There were some birdies produced on 20-15-10 only when the taillights were turned on, but since these are mainly daytime bands it wasn't a big issue. I also used some toroids on the taillight wiring to reduce this RFI somewhat. The 160-meter noise floor was so quiet I could often hear stations from the mobile that fixed stations with exotic antennas could not hear while I was driving on a Delaware rural expressway with no nearby power lines (Route 1).
The only issue I had with transmit RF getting into the car electronics was with the 2000. When transmitting with 100 watts on the 40-meter band, it would shut down the cruise control. Reducing power on that band to 30 watts eliminated the problem.
The worst receive birdies were with the 2009, mostly on the 20-meter band.
In general I found mobile operation a pleasure with these cars during the years I had an hour-long commute, mostly on an expressway, from central to northern Delaware. I worked 272 "countries" as defined for ham radio purposes, including 54 on the 160-meter band.
I had some pix on my ham-radio website but they are currently down while that is under re-construction, but I will try to get them back up soon.
73/Jon AA1K
www.aa1k.us