[Vwdiesel] 2 way radio antenna placement

[Lee Hillsgrove]

> I'm wondering if anyone can comment on 2 way radio antenna placement
> on a TDI.  I have an '03 Jetta TDI, which lacks installed ham radio
> equipment.  I'd like to install a dual-band radio 2m (146mHz) and
> 70cm (445mHz), and a permanently mounted antenna.  I'm considering placing
> a 2m 1/4 wave antenna in the center of the roof.  When ECUs started
> coming out on cars I recall problems that people had with the placement
> of antennas, and their effects on the operation of the engine.
> Can anyone comment on the sensitivity of VW equipement to RFI?
>
> My intended power would be on the order of 50W.



  Well, I have a '98 Jetta in which I have installed a Kenwood TM-V7A dual
band in the cubby in front of the shifter, rated at 50W on 2M and 35W on
70cm. I am using a Comet trunk lip mount and a 55" tall Comet SBB-7
fold-over antenna which is rated at 4.5dB gain on VHF and 7.2 dB on UHF. The
antenna is mounted on the left side of the trunk. I have had this in place
since last summer and have had absolutely no problems with RFI at any power
level, if you discount the fact that my radar detector goes banannas
whenever I transmit on UHF. I have a friend with an '01 or '02 Jetta who is
running a FT-90 remote mounted in the trunk and connected to a slightly
smaller dual band antenna, also lip mounted on the trunk. He has also had
not had any RFI problems that I know of so far. Also have another friend
with a '98 NB, running 50 and 35 watts through a high-gain antenna
lip-mounted to the trunk, no problems. While these are not permanent mounts,
I should think that the ERP I'm producing in my car and the others I know of
would have caused problems if the ECU was going to have issues. I should
think a roof-mounted 1/4 wave would present even fewer potential problems.

Bravo for being willing to drill a hole in the roof of your brand-new car!
You're a bigger ham than I am.  :-))  Actually, I wanted the lower mounting
position because my antenna is so tall and it does not have any type of
spring mount. I would be afraid of whacking it on a tree or something and
breaking it off. As it is, I have to remove it if I go into a parking
garage. I went for a high-gain antenna because the terrain around here is
pretty hilly and I wanted all the advantage I could get.

 I have used a 5/8 wave RS 2 meter mag-mount on the center of the roof of my
A2 Jetta with good results. Looking through the sunroof on the highway, the
tip of the antenna would be bent back to the viscinity of the rear window
from the breeze at 65 mph but I never lost it, even up to almost 100 mph.
(yes, in a 1.6 NA, on a long flat which followed a downhill grade. hehe!)


>
> I'm also concerned about high RF levels on the "Monsoon" radio.  Not
> so much in desense, as I expect that.  Rather, I'm concerned with
> front end damage, as the antenna is roof mounted near the center by
> the back window.


 Can't comment on the Monsoon since I don't have one, but I have had no
problems with the factory unit in my car. My antenna is mounted on the left
front fender, though. My friends with the A4 and NB have not mentioned any
problems with theirs, and I think they have Monsoons. Those antennas on the
trunk are approximately as far away as yours would be in the center of the
roof from the radio aerial, I think.

 One of the guys on the TDIclub has an A4 Jetta and runs HF mobile with an
antenna mounted through the center of the trunklid. I don't recall him
saying anything about the radio, but I know he has said he has to run low
power or the RF gets into the rear defroster grid and causes all kinds of
screwy behavior.


Hope that helps, feel free to ask if I forgot something.

Shameless plug - Sandy Cameron and I had a most enjoyable QSO through
Echolink last night. Worked excellent! It would be nice to get others
involved. (hint, hint!)  :-))


  Lee
  Oo-v-oO
  PP-ASEL
  KB1GNI