steve200TDi Posted October 31, 2018 Share Posted October 31, 2018 12 hours ago, Happyoldgit said: You should get continuity from the centre of the PL 259 plug up [centre conductor of coax] to the antenna whip. Likewise continuity from the outside of the plug, through the coax shielding up to the plug or mount connection at the antenna. The mount, or parts of it, should generally be in good metal to metal contact with the body of the vehicle. What mount and antenna are you using and where do you have it located. An off the scale SWR sometimes indicates a short between the coax centre and shield or connected parts. Don't start chopping bits off the whip as you can't glue them back on! When I was installing this stuff many, many years ago I would carry lengths of cheap rod to use when working on those on tricky installations. 14 hours ago, Red90 said: Can you take a picture of the mount and the wiring connections? It's a side mount and I have put rubber insulation around the roll cage tube that sits in front of it. When I unplug the PL259 from the cb radio I don't get continuity. Steve Quote Link to comment Share on other sites More sharing options...
Tanuki Posted October 31, 2018 Share Posted October 31, 2018 In your photo it looks like the top part of the coil is actually forced up-against the roll cage to the extent that the coil is being bent back. Even if you try to put any insulation between the roll-cage and the top of the coil, it won't work - the issue here is electrical *capacity* between the earthed roll-cage and the bit of the coil that's close to it. This will detune the antenna causing all sorts of unpredictable effects. Also, the coil looks horribly close to the drip-gutter, which will also add further undesirable capacity. Relocate the antenna so there's no metalwork within six inches of the top of the coil or any part of the whip. A "clamp mount" on to the rollcage itself would be a good move, provided the rollcage is properly earthed. Quote Link to comment Share on other sites More sharing options...
Ex Member Posted October 31, 2018 Share Posted October 31, 2018 Let's see the connection of the wires to the side mount. Those mounts can be quite fussy. Quote Link to comment Share on other sites More sharing options...
Peaklander Posted October 31, 2018 Share Posted October 31, 2018 5 hours ago, steve200TDi said: When I unplug the PL259 from the cb radio I don't get continuity. That’s the problem. There should be continuity between the centre of that plug and any / all of the metal of the whip. Quote Link to comment Share on other sites More sharing options...
Happyoldgit Posted October 31, 2018 Share Posted October 31, 2018 Hmmm. Folks tend to locate those mounts abobe the gutter on the rear panel to avoid the issue you have of the whip and coil being in close proximity to the gutter. You have the added complication of the roll cage being close to the whip as well which as previously said is an undesirable state. With that roll cage you have an issue. If the cage does not have an antenna mount tab welded to it [you could add one of course] I would either mount the antenna on the horizontal roof panel fairly close to the rear edge so as to be accessible or take a slight hit on performance and mount on top of the front wing on the opposite side to the standard radio antenna. Quote Link to comment Share on other sites More sharing options...
steve200TDi Posted November 8, 2018 Share Posted November 8, 2018 So.... I have a confession! I plugged in the SWR the wrong way round. I did not realise that a) that it had polarity and b) it has Ant and Tx on the front corresponding to the rear connections! Anyway, I fitted a new antenna mount and even fitted a new antenna too as I had a spare! And I trimmed 35mm off of it to reduce the SWR to 1.5 - 2.5. So we'll see how it performs this weekend! Oh and out of interesting I tested the existing antenna and mount the SWR was over 3! Thanks for all the help. Steve P.S. Sorry, the forum moved the picture round like that - It wasn't me! Quote Link to comment Share on other sites More sharing options...
Happyoldgit Posted November 8, 2018 Share Posted November 8, 2018 Good, good. Best ditch that old antenna as it could potentially affect the SWR and performance of the new one. Quote Link to comment Share on other sites More sharing options...
Ex Member Posted November 8, 2018 Share Posted November 8, 2018 Make sure you understand how to use the meter. If you got the wire backwards, I'm a little worried that you did not read the descructions. You need to calibrate the meter every time you check. Quote Link to comment Share on other sites More sharing options...
steve200TDi Posted November 8, 2018 Share Posted November 8, 2018 Oh yes, don't worry I have removed the old antenna! And Yes I understood about doing the checks on each setting on the SWR, I just didn't realise that it had polarity going through it! Steve Quote Link to comment Share on other sites More sharing options...
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