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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
