Disco 2 Citizen Band Radio engine noise

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ironhorse

Active Member
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280
Location
West Sussex
This may have been asked before but I can’t find anything previously posted about it so if it has I apologise, my question is related to Citizens band radio, and I’ve just fitted a new one into my disco 2003 td5, it is SS6900 I’m not new to cb just in this car, aerial base is bolted through the rear wheel hanger and the coax is run through the door then up to the roof along the passenger side to the front above the passenger sun visor which I have removed and bolted the radio in that place so all controls and face points at the driver, power line goes down the windscreen pillar back and along the front of the glove box and I’ve soldered a fag lighter plug onto it and pick up the power from the faglighter port just in front of the H/Low gear stick, but when I start the engine I am getting engine interference of around 5lb on the radio meter the interference will drop if I lift my foot off the accelerator and rise again when I put my foot down, however it will also rise once static with engine running so it’s not just linked to driving along, I have tried connecting the power from the radio directly to the battery but no difference at all, can anyone throw any light on this problem, earth straps are ok.
 
ironhorse said:
This may have been asked before but I can’t find anything previously posted about it so if it has I apologise, my question is related to Citizens band radio, and I’ve just fitted a new one into my disco 2003 td5, it is SS6900 I’m not new to cb just in this car, aerial base is bolted through the rear wheel hanger and the coax is run through the door then up to the roof along the passenger side to the front above the passenger sun visor which I have removed and bolted the radio in that place so all controls and face points at the driver, power line goes down the windscreen pillar back and along the front of the glove box and I’ve soldered a fag lighter plug onto it and pick up the power from the faglighter port just in front of the H/Low gear stick, but when I start the engine I am getting engine interference of around 5lb on the radio meter the interference will drop if I lift my foot off the accelerator and rise again when I put my foot down, however it will also rise once static with engine running so it’s not just linked to driving along, I have tried connecting the power from the radio directly to the battery but no difference at all, can anyone throw any light on this problem, earth straps are ok.
Click to expand...
Old Haynes manuals used to have a lot on how to fit a radio and suppress noise. I can remember fitting suppressors and condensers all over the place. can even be a question of whether the bonnet is earthed to the body!
Does your ordinary radio suffer too?
You could try using coax cable , i.e. the inner wire, for the positive, so the outside wire shields it, but best of luck anyway.
I take it the aerial is properly "grounded"? Where it is there may be a lot of interference from vibration, but I doubt it'd happen at standstill.
Used to fit them in kit cars which could be a right pain, but we needed them when doing convoys.
Might just need a filter.
 
Stanleysteamer said:
Might just need a filter.
Click to expand...
:D :D

Z(14).jpg
 
Alternator was replaced with a new unit a few weeks ago, Rear wheel bracket that is bolted to the rear door, swr is fine aerial clears wheel and door although yes a little bit direction.
 
ironhorse said:
Alternator was replaced with a new unit a few weeks ago, Rear wheel bracket that is bolted to the rear door, swr is fine aerial clears wheel and door although yes a little bit direction.
Click to expand...
We found that the ground plane when fitted to the chassis on a kit car wasn't very good, obs, but then we didn't have steel roofs to fit a mag mount to! On the wife's old kit car we mounted a plate to her spare wheel on the back of the car, that worked OK-ish. .
 
As I say Alternator was my first port of call but as expected a new unit all ok, power cable was my thought coming in there but no, when I first fitted the radio because of the distance from back to front for the aerial coax I had to buy more to reach properly, as my original length was two pieces, my first two pieces gave a very good SWR, new wire obviously I had to soldier new plugs either end, suspected may be a problem there as SWR was a little higher but after checking with meter all looked to be fine there, now as said by one of you chaps just now I was about to pull the aerial connecter off the back of the radio to just eliminate that thinking well I’ve already checked the coax for problems but low and behold plug out interference dropped, so it pays sometimes to check and check again I should know that, Thank you gentlemen for helping I shall now have a serious talk with myself.
 
ironhorse said:
As I say Alternator was my first port of call but as expected a new unit all ok, power cable was my thought coming in there but no, when I first fitted the radio because of the distance from back to front for the aerial coax I had to buy more to reach properly, as my original length was two pieces, my first two pieces gave a very good SWR, new wire obviously I had to soldier new plugs either end, suspected may be a problem there as SWR was a little higher but after checking with meter all looked to be fine there, now as said by one of you chaps just now I was about to pull the aerial connecter off the back of the radio to just eliminate that thinking well I’ve already checked the coax for problems but low and behold plug out interference dropped, so it pays sometimes to check and check again I should know that, Thank you gentlemen for helping I shall now have a serious talk with myself.
Click to expand...
Always happy to help!:):):)
 
ironhorse said:
No it’s not right at all I’ve re-check coax all fine removed rear wheel re-checked SWR 1.1 but as soon as I fire up the engine 5lb noise SWR high, turn engine off SWR remains around 2
Click to expand...
Oh dear, back to the drawing board, but at least you've eliminated the coax.
Just for fun why not tap into the ornery radio feed, just to see what you get?
 
ironhorse said:
No it’s not right at all I’ve re-check coax all fine removed rear wheel re-checked SWR 1.1 but as soon as I fire up the engine 5lb noise SWR high, turn engine off SWR remains around 2
Click to expand...
So one minute "plug out interference dropped" but next you've checked it and it's fine. Do you have another antenna with a mag mount you could use for comparison?
 
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