This information is now 20+ years out of date, so I don't know what the
car companies do any more about HF EMI testing (if anything). Some of my
radio buddies were employees of Ford, and they would arrange to drive
new/developmental cars around under the antenna field at the old VOA
relay site north of Cincinnati. Maybe nobody worries these days, but I
do know that the manufacturers are VERY sensitive to anything that
creates a driveability issue.
73...
Randy, W8FN
On 5/6/2019 12:23 PM, Dave New, N8SBE wrote:
Most modern vehicles are tested for EMC in large chambers, where they
are bombarded by high-power frequencies that extend up into the
microwave range. So, they are relatively immune to external RF fields.
On the other hand, they are frequently not designed to withstand a
powerful onboard transmitter, unless specifically designed for a
particular market, say police/fire/ambulance.
In the case of those vehicles, the assembly plant typically installs
bonding/ground straps to bond all major metal panels. Unfortunately,
regular customers can't get those kits installed at the plant for them,
and they aren't very effective as an aftermarket kit, because the
customer would have to scrape the paint down to bare metal and access
locations that might be completely closed off after assembly to install
said straps.
The other unfortunate effect of designing for police/fire/ambulance
service, is that all those radios are now VHF/UHF and up. No more HF
radios. They went out with the state-wide sheriff's networks of old
that ran on 40 MHz or so. So, that leaves the amateur radio HF operator
twisting in the wind, both for onboard interference from vehicle
electronics, and susceptibility of same.
I heard that one OEM had declared that no one used HF any more, because
they scanned the FCC database looking for amateur station assigned
frequencies (ala commercial stations which are assigned fixed channels
or groups of channels) and finding none, reached the conclusion that no
one is using those bands any more. Thus, all frequencies below 30 MHz
are not protected, except for the AM broadcast band in the US, and MW in
the EU.
OEMs are concerned that their onboard entertainment radios
(AM/FM/Sirius/XM) and their tire pressure monitor and remote keyless
entry systems have no interference, but everything else can go to pot.
At one time, I'm aware that at least one OEM tested using an Icom IC-706
with those dummy-load like 1-inch coil resonated antennas, but I don't
know if that is any longer the case.
The ARRL TIS (Technical Information Service) maintains a database of
information on mobile installations, including official documentation
(if any) from various vehicle OEMs on suggested mobile installation
guidelines. Some OEMs used to come to Dayton with sample mobile
installations, and answer questions but I've not seen them do this for
some number of years.
Hope this helps.
73,
-- Dave, N8SBE
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