Dual antennae...

AB7IF, what do you know about the multiplexor setups used in some trucks such as the Volvos and the Peterbuilts??? Just wonderign because I have had issues in the past with two trucks that had these types of setups in them. Warning lights, high swr etc. This setup is supposed to eliminate the need for a seperate am/fm radio antenna. Some say that the weather portion of the stock am/fm radios may not work unless you use the factory fiberglass style antennas.

My current truck has the multiplexor box setup in it. I ended up bypassing it by running seperate coax to the CB antennas and running a new coax and seperate AM/FM antenna to the center of the roof.

But I see alot of guys using the stock setup but removing one of the antennasor they will actually cut the coax to one of the antennas. Their radios don't seem to have the range that they should have in my opinion. They don't seem to have the ears they should either.

Is this an issue or does the box make up for the loss of the extra antenna and not let the radio see high SWR????

 

Splitters between truck models/years are not all the same so one answer does not fit all, other than usually a capacitor is blown in the splitter when too much power is run through. This assumes some other problem like a bad antenna or coax is not the culprit. As to bypassing it depends upon the unknown of what they actually did to bypass it, which involves their skill. Often this is the problem. They are easy to take apart, and finding the usual blown capacitor is simple, being replaced without much trouble. The Volvo style splitter is not hard to bypass but adding two PL's with a short barrel connector is the best way to go. This leaves the other antenna for the in dash radio and cell connector to function. Your last question is hard to answer without actually seeing what was done. I have not seen problems with weather radio off a simple Francis antenna on say a 29 WX, but the trap antennas may depend upon reactance in the splitter to function correctly. Have not studied the newer trucks and their trap antenna system so unsure on that one.

 

I can vouch that the antenna systems on the Freightliner Cascadia models are junk. Even the ones I have checked and that have a good SWR do not xmit over 1 mile, or hear much further either. When I meet one of our trucks on flat level ground, we lose each other while still in sight of one another!! They do seem to talk forward better than to the rear.