Mobile Muddle revisited

Armed with all the information I headed to the Kia Carnival to do battle. Started by pulling the Mag mount to pieces to see how it was put together. Pretty basic but lots of room to attach earth leads to. Used Sticky aluminium tape to run from the pl259 down to the roof and accros to the roof rack mounts on both sides. Luckily I was able to ground it to the roof at this point.
Put the antenna back together and hooked up the radio, amp and SWR meter.
Radio all OK SWR 1:1.2 or so.
Turned on the Amp and the SWR came in at about 1:1.2 also at lowest point but the curve was very sharp.
Resonant frequency seems to have gone down 300k/cs but reluctant to cut more off the whip until I get it out in the open. Testing it too close to trees, wires and house right now. Didn’t make much difference with the 30w but could be affecting readings with hi power. Battery must be a bit flat as lights dimming. Still it was putting out 320W or so FM with 30W drive. Checked the voltage drop at the amp and it was 13.8 dropping to 11.4 with Engine running. Power had gone up to 400W FM. Checked the leads and they were warm. Oops. I had doubled them up and they looked pretty big but they were quite flexible so did not have much density. Luckily I had bought some thicker wire just in case. The new wire was just under 1/4" diameter. The copper part and quite stiff. Ran it back to battery and wrapped the cables in the sticky foil as well. Bit of heat shielding for the wires in the engine compartment.
This time the lights don’t dim and the Amp is reading close to 500W. Car radio comes on but as the vehicle is diesel I hope it can’t do much else. Need to find an open area to check the SWR properly before cutting any more off the whip. I did not earth the Amp but I will when I work out where I will put the amp in the car. It is nice to have it visible so you can turn it off and on easily and still be able to take it out without too many hassles when needed.
Starting to wonder if the hassle of having the amp in the car is worth it…..
But we are well on the way to fixing the hi SWR with the magmount. Definitely needs earthing on the roof.
Just need to trim it too frequency and earth the amp to a pillar or chair bolt.
Thanks for everyone’s help especially Aja and Glen from down in the land of the kiwi.
 
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2 Responses to Mobile Muddle revisited

  1. Unknown says:

    Hello,well looks like youre getting there BUT sticky alloy tape to make an earth?????Use the real thing, braiding,anything that does not make solid contact WONT DO.Its like the magnet it will do so much then say " up to you too"You cant beat a bolted, screwed or soldered joint for earth OR supply.I know you live in Indonesia but sticky tape for earth, gosh thats like you hair colourall over the place except where it is supposed to be.Goog thing your name is Dave not Richard otherwise we would have to call you "spotty Dick"Bye got to go now before I get myself in trouble here. Bye, Grey and proud of it, earned every hair of it!

  2. Dave says:

    Spotty Dick???? How do you know??? Who\’s been talking…..No worries mate…!!!HoweverRe the grounding…(Back on safe ground)Aja….Very clearly stated. Glad I don\’t owe you any money!You are quite correct in your condemnation of the aluminium foil proceedure I used. The aim here was not a permanent set up but to find the cause of the problem and then to work out the solution. Did not want to drill holes in the roof at this stage.In my defence…The foil is industrial and quite thick and 2" wide and can be run on, in and around most things on the car. Sticks to the car roof real well! I also ran out one length along and down inside the back rear door (5th) to give me a 9\’ length as a counterpoise. The foil makes contact to the earth in 2 places where it passes under the fixed plastic roofrack that comes as part of the car and a screw can go through the fitting and the foil. Checked the connection between the foil and the earth of antenna coax and it reads 0 resistance. Doors are sliding and it does not have a \’gutter\’ to get back to the body ground with. Next step will be to remove the mag mount and use braid from Magmount coax ground to the screw of the roof rack to ground it at that point on both sides. (and ground the amp) Need to get out in the open to see what has happened to the SWR. Our drive is surrounded by trees so not the best. Frequency is lowered about 500k/c at resonance when parked in our drive.

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