CJ1 Posted August 25, 2014 Share Posted August 25, 2014 Hi, I used the factory placed hole in the roof near the rear sunroof to fit a DV27 aerial base and fitted a 1.55m coil loaded aerial and a 4 meter aerial lead that I bought at that length. I used an SWR meter and the first readings were 2..1 for channel 40 and 2.6 for channel 1. So I raised the aerial bit by but until it was adjusted to the full length it can go and got the readings down to 1.6 for channel 40 and 2.1 for channel 1. Has anyone else fitting CB Radio's and aerials to there Discovery 2's had the same or similar problems? If so did you manage to get it sorted? Cheers Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted August 25, 2014 Share Posted August 25, 2014 Did you take the paint off the roof where the base fits? You need to ensure there is good connectivity. It should be easy to get a better vswr than you report if all the cables, connectors and the ground connection are good. Quote Link to comment Share on other sites More sharing options...
Anderzander Posted August 25, 2014 Share Posted August 25, 2014 Those numbers aren't too bad though are they ? A reading of below 1.5 is ideal A reading between 1.5 and 2 is ok, and nothing to be worried about A reading between 2 and 2.5 will usually be reduceable with adjustment to the aerials length A reading between 2.5 and 3 usually indicates that the aerial is being affected by something around it, or that the groundplane is present but maybe not big enough A reading in the red part of the SWR meters' scale means that the SWR is high enough to possibly damage the set and usually indicates an insuffcient ground plane/earth connection, or a short or open circuit in either the cable, plugs or mount. Quote Link to comment Share on other sites More sharing options...
honitonhobbit Posted August 25, 2014 Share Posted August 25, 2014 Chuck an extra earth on Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted August 25, 2014 Share Posted August 25, 2014 Don't chuck an extra earth on - make sure the only earth that matters is correct. +if+ you were after the last 10th of a db improvement you could bond the roof to the sides of the vehicle but your not so don't bother. Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted August 25, 2014 Share Posted August 25, 2014 Did you take the paint off the roof where the base fits? ....... ..... take the paint off on the inside of the roof 1 Quote Link to comment Share on other sites More sharing options...
Tanuki Posted August 25, 2014 Share Posted August 25, 2014 Which set of channels are you using? There are old-style UK CB27/81 channels, and Euro-channels. The precise length of antenna needed varies between these. Not all antennas can necessarily be tuned to give a good SWR on all channels! As others have said, make sure the antenna-base is properly grounded to the roof. This will involve getting friendly with the sandpaper/wire-brushes. 1 Quote Link to comment Share on other sites More sharing options...
CJ1 Posted August 25, 2014 Author Share Posted August 25, 2014 I have an old Midland CB radio with uk only channels and only has 40 channels on it. Next weekend if the weather is good I will get the roof lining back down and scrape the roof more. Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted August 25, 2014 Share Posted August 25, 2014 Also if its a td5 make a comparison between engine running and engine off. td5s are incredibly noisy generating so much interference that hf reception is a real challenge Quote Link to comment Share on other sites More sharing options...
CJ1 Posted August 25, 2014 Author Share Posted August 25, 2014 I will try it with the engine on tomorrow. And yes it is a TD5. Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted August 25, 2014 Share Posted August 25, 2014 Ok engine on will only make matters worse as the noise level will increase. So check the ground connection at the antenna. Good luck Quote Link to comment Share on other sites More sharing options...
CJ1 Posted August 25, 2014 Author Share Posted August 25, 2014 Just been out and tried it with engine on and I couldn't hear any difference between engine off or on even the readings on the swr meter came back the same as if it was off. Quote Link to comment Share on other sites More sharing options...
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