[Vwdiesel] 2 way radio antenna placement

Mike & Coreen Smith ve9aa at nbnet.nb.ca
Tue Apr 8 19:42:42 EDT 2003

Having been a ham for 25 years now (am I really that old?, oh my !) The only
real time I have had real big problems with radios interferring with ECU's
or anything else was when I was running 100w from an old Hot Water 1-oh-1
(HW-101) and using a huge WEbster Bandspanner antenna.  For those that are
not hams, this is gobs of power, and in the "HF" region. (3.5-29.7MHz)
The wipers on my car would go, (on their own) when transmitting.
I have had a few cars sputter ever so slightly when running 90w on 6m or HF
with antennas in different locations.
I have had SO MANY radios and antennas on so many vehicles I have lost count
years ago.  Don't run your coax under the carpet next to an ECU (or whatever
your ECU is located, lol) and problems will probably not appear.

Purely from a "best location for an antenna" ERP-wise, center of the roof is
it.  Get it down on one of the fenders and you are shielding part of the
antennas field and it "could" create problems with RF getting into nasty
places you don't want it.  Also various SWR problems "can" occur.

73 de VE9AA (Translation: best wishes from Mike)

----- Original Message -----
From: "Lee Hillsgrove" <hillsgrove at adelphia.net>
To: <vwdiesel at vwfans.com>
Sent: Tuesday, April 08, 2003 10:17 AM
Subject: Re: [Vwdiesel] 2 way radio antenna placement

> > 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
> > 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.
> 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
> 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
> 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
> I should think that the ERP I'm producing in my car and the others I know
> 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
> 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
> A2 Jetta with good results. Looking through the sunroof on the highway,
> 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
> 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
> 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
>   KB1GNI
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> vwdiesel at vwfans.com
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