Does any one know a bit about UHF antennas & Federal Signal Smart Vector light bars? Here is my problem I have a UHF 470 band antenna that is causing RFI with the micro procosser on a light bar. It only effects the "smart pods" of the light bar (example: when the raido is keyed up the smart pods will freeze up and the light will go off). If anyone has any suggestions please reply.
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Thanks Eric
Hello Eric,
I've been in the emergency vehicle business for 12 years and this is a first. It is highly unlikely that the RFI would cause interference with the micro processor on the lightbar because of two reasons. It isn't dependent on radio frequencies and it is surrounded by metal which is normally grounded. Few things you can try,...
Check to make certain the ground is solid and clean in the lightbar and at the battery. Yes, the battery, not a convinent ground source. Both the radio and the lightbar should be at the battery for ground. Intermittent ground does strange things sometimes.
Check the antenna connections. Is it secure? If you have access to a radio technician, have them test the antenna with a watt meter specifically made for this purpose. Also, is the antenna at least 18 inches from the lightbar?
Check to make certain that you have ample power supplying the lightbar. If keying up the radio draws a hefty current from the radio, it "could" affect the power sensitive smart pods. lastly, smart pods have these sensors that detects the positions of the rotators. The older versions uses light colored sensors and the later versions were all black. It was known for the sun and other bright direct sources to confuse the sensors. The black sensors corrected the problem.
Hope it helps.
Sean - Emergency Vehicle Solutions
I have been in the emergency vehicle for the past 6 years this is also a first for me. the vector bar was brand new out of the box with all of federal signals upgrades (farrit beads & cap upgrades). I talked to federal and the admit their is a problem but have to me the updates should have taken care of it. I put both of the grounds (light bar & radio) to the battery but it did not hepl me any all of this was done prior to posting this.
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Thanks Eric
Eric
I'll ask around and see what I know and what we learn, we'll share. How's that?
Sean
sounds good to me.
Eric,
I asked a good friend of mine who's been in this longer than I have. He mentioned that he has come across some vehicles with that problem. The antenna needs to be at least 18 inches from the lightbar and if the radio is a high-wattage device (150 watts thereabouts) then grounding straps needs to be installed everywhere such as between the cover and the chassis of the lightbar, between the chassis of the lightbar to the vehicle chassis. If you employ the Smart Siren, the chassis of that would need to be grounded as well. The grounding straps have a very fine wire count and usually flat & braided. Also, the cable route between the vehicle and the roof needs to be protected with a metal conduit. The metal conduit helps shield the cable from stray RF.
Another factor is improper antenna length. Reflective power can increase stray RF as well, hence the watt meter as mentioned earlier.
BTW, what vehicle is it anyway?
Sean
Coming in a bit late on this one but try re-locating the antenna to the trunk lid. Removing the antenna from the same plane can make a difference. Also make sure the contact on the bottom of the antenna as well as the cable assembly are clean and shiny, use emery cloth to clean and do not employ dielectric grease as a corrosion inhibitor. Is the antenna a high gain type or a simple quarter wave? Hope this helps but I am afraid I'm probably too late to be of service.
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R Jackson
Owner/Installer
TRM Emergency Vehicles
Information is advice only and should be confirmed with OEM or quality test equipment.
Boyertown, Pennsylvania