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Car Forum / Australian Car Forums / 4x4 Cars (Australian group) / January 2005AM CB in Pajero.
Hi all! I have just installed an AM only CB in my NJ Pajero. Please don't ask "Why?" You will not get a response! I am only looking for helpful, intelligent assistance here please. (Is that a contradiction in terms for a newsgroup?) :-) Problem is: Unit is nice and clear when engine is off. When engine is running, I get major noise. So much noise that I need to have the squelch up at least 50% to cut it out. Noise is MASSIVE with ANL switched off, but flick the switch and it cuts it down quite a bit but still noise registers as 2 lights on the signal strength meter out of a possible 4 lights. Noise is clicking, as if in time with spark plugs etc, and increases with acceleration. Unit is a Uniden Pro 510xl. Antenna is mounted on a bullbar. SWR has been checked and corrected. I have heard conflicting advice on this so far. Some say noise filters are available and will work. Some say there's nothing you can do about it. Some say that Pajero's are inherently bad for ignition noise and nothing can be done. Has anyone here had any experience with this problem, either in Pajero's or with clearing bad ignition noise? Please reply here with any help. Thanks. CKL Have you checked yoru earthing on both the antena (If applicable) and the head unit. Please dont tell me that you have run a wire to the battery for +ve and -ve for best performance. A solered ring earth lug is best and usually the dash steel is good enough. Other than that try reroute your +ve feed from where you have fed it from. Try the battery direct (Via a fuse) to the head unit. Also you may have to reroute your coax lead. Its also a dumb sounding question but have you got the correct polarity at the antenna, easily done wrong. Try them and post back how you went. Hope that helps Scotty > Hi all! I have just installed an AM only CB in my NJ Pajero. Please don't > ask "Why?" You will not get a response! I am only looking for helpful, [quoted text clipped - 19 lines] > Please reply here with any help. Thanks. > CKL The antenna should be earthed ok as far as I know. I had the SWR checked by a car stereo/communications place, so I hope they would have checked the antenna earth and polarity before adjusting the SWR. My +ve line runs direct from the battery, with the standard fuse just before the unit. I've run the -ve to the sidewall of the engine bay (next to the compliance plate). I thought of re-routing the coax, but the gas conversion crap is all on the other side, and I didn't know if that would be even more interfering. I'll try it and see how I go. Thanks for the advice. I'll post results as they happen. CKL > Have you checked yoru earthing on both the antena (If applicable) and the > head unit. Please dont tell me that you have run a wire to the battery for [quoted text clipped - 33 lines] > > Please reply here with any help. Thanks. > > CKL if the noise is still there get some ferrite beads and wrap the power cable through it a few times(the more the better) and also do the same with the coax cable the noise is ignition, so running the coax and power cables past the Gas converter would not be a problem Kev > The antenna should be earthed ok as far as I know. I had the SWR checked by > a car stereo/communications place, so I hope they would have checked the [quoted text clipped - 53 lines] > > > Please reply here with any help. Thanks. > > > CKL I quick hint. Fuses are there to protect the cable as well as the unit! Either relocate the fuse to within 300mm of the battery or add another there. Ive seen way to many cables catch a car alight due to no fusing. The fact that you have also earthed your unit at the fire wall leads me to suggest another relocation. Try use the dash metal. Solder the lug to the wire if you are able to. > The antenna should be earthed ok as far as I know. I had the SWR checked > by [quoted text clipped - 60 lines] >> > Please reply here with any help. Thanks. >> > CKL I somehow missed this post! I'll try it. I originally thought I'd get the CB as a replacement for the normal stereo, as it kept cutting out all the time. When I went to remove it, and replace it with the CB, I discovered that some numb nut had disconnected the earth wire, and it was cutting out as the loose earth wire flapped on and off the dash metal! Hooked it to the dash metal and it's been fine ever since! Might try and hook the CB earth to the same spot, at least I know it's a good earth position, and it's only about 10cm from the CB instead of a metre or more. Will try it this weekend, and advise! CKL > I quick hint. Fuses are there to protect the cable as well as the unit! > Either relocate the fuse to within 300mm of the battery or add another [quoted text clipped - 67 lines] > >> > Please reply here with any help. Thanks. > >> > CKL Try and solder it if you can, makes for a more permanant join and better electrically. Dont forget your fuseing. You could also try and feed the CB from the radio feed for another excersise, just to see if that makes it better or worse. >I somehow missed this post! > I'll try it. I originally thought I'd get the CB as a replacement for the [quoted text clipped - 98 lines] >> >> > Please reply here with any help. Thanks. >> >> > CKL If I'm to put a fuse at the battery end, what size should it be? Same as the one at the radio end? > Try and solder it if you can, makes for a more permanant join and better > electrically. Dont forget your fuseing. You could also try and feed the CB [quoted text clipped - 103 lines] > >> >> > Please reply here with any help. Thanks. > >> >> > CKL No one size up will do nicely. All depends on size of cable. Work on around 5 amps per mm squared if using multi stranded type cable (many many strands of fine copper rather than 5 or 6) If you are using say a 1.0 mm cable and the radio draws around 3 amps (Full load) fuse should be around the 5 amp at the battery end and 3-4 at Radio end. Remember the fuse at the battery is there to protect the cable from setting the car alight on a dead short 1/2 way in and the fuse at the unit is there for fine protection of the unit, that fuse has nothing to do with the cable protection. I've seen quite a few small fires in cars where the duffus's have put no fuse or fused at the wrong end. VERY messy! > If I'm to put a fuse at the battery end, what size should it be? Same as > the [quoted text clipped - 129 lines] >> >> >> > Please reply here with any help. Thanks. >> >> >> > CKL Just a thought before I start screwing around with this. If I leave the antenna where it is, and re-route the antenna coax, will I bugger up the SWR? Surely it should remain unaffected as the coax is still the same length? CKL > Have you checked yoru earthing on both the antena (If applicable) and the > head unit. Please dont tell me that you have run a wire to the battery for [quoted text clipped - 33 lines] > > Please reply here with any help. Thanks. > > CKL >Just a thought before I start screwing around with this. If I leave the >antenna where it is, and re-route the antenna coax, will I bugger up the >SWR? Surely it should remain unaffected as the coax is still the same >length? Correct. Just don't wrap it around the alternator or similar :) Seriously - ensure there are no multi turn loops in the feed co-ax these may (or may not!) cause problems. Mike Harding Nice fence sitting Mike. Co-ax lenght is relatively unimportant. The main thing is that it is terminated correctly. IE. That there isn't a gap between the dielectric around the core and the outer braid where the PL295 is soldered on. Assuming you are using the thin 50ohm stuff. Anyway, you will get pretty tired of the pore quality of AM CB fairly quickly, even though no one else uses it any more except you and your mates, and it will cease to be a problem for you. Cut to the chase now and get a UHF. have a good new year, don't do anything dumb. C ya in the bush, maybe. > >Just a thought before I start screwing around with this. If I leave the > >antenna where it is, and re-route the antenna coax, will I bugger up the [quoted text clipped - 7 lines] > > Mike Harding > Anyway, you will get pretty tired of the pore quality of AM CB fairly > quickly, even though no one else uses it any more except you and your mates, [quoted text clipped - 3 lines] > > have a good new year, don't do anything dumb. C ya in the bush, maybe. LOL! At least you didn't ask 'Why?'! Sorry, kept forgetting to water my money tree man, and now it's kindling! Truth is, it won't even be just me and my mates. I don't know anyone with a CB of any description. I paid $12.50 for the thing off Ebay. A wife, a 22 month old, and the one about to be born at the end of February are keeping that money tree well and truly trimmed. You could almost call it a Bonsai! I'll be content just 'sandbagging' for a while, and maybe having the odd chat with someone. (assuming I can find someone who doesn't just whistle, or play heavy metal over the air!)First job though is to clear up this interference. CKL I think a lot of the truckies still have am radios..especially Sydney to Melb...well that was a few years ago > > Anyway, you will get pretty tired of the pore quality of AM CB fairly > > quickly, even though no one else uses it any more except you and your [quoted text clipped - 16 lines] > interference. > CKL OK, Have just re-routed the coax, AND the power lead so they now go round the complete other side of the car. No difference. Still getting 2 out of 4 signal lights when engine is running. Someone I was talking to this morning said to try a "floating ground", or "floating earth". Can't remember which they called it. Does this make sense to anyone here? I guess because the re-routing didn't work, I should try the noise filters next. Ideas? CKL > >Just a thought before I start screwing around with this. If I leave the > >antenna where it is, and re-route the antenna coax, will I bugger up the [quoted text clipped - 7 lines] > > Mike Harding try the ferrite bead idea the noise is getting into the radio through either the power cable or the outer shield of the coax you could also try a condensor on the altinator what is the AM signal like on your car radio, is it noisy as well? also don't be afraid to use the ANL/NB switch, it will not make it harder to hear a signal, just cuts the type of noise you are getting Kev > OK, Have just re-routed the coax, AND the power lead so they now go round > the complete other side of the car. No difference. Still getting 2 out of 4 [quoted text clipped - 17 lines] > > > > Mike Harding If I use ferrite beads, don't I have to find out what frequency the interference is? How do I do that with a piece of string, a paper clip, and a peanut? (That's about all the specialist equipment I have!) :-) The AM on my normal stereo does not have the interference. I have already got the ANL switch on. It makes a huge difference to the noise level. I noticed something yesterday that may help diagnosis. As it's a 1.5 metre whip antenna on the bullbar, it won't fit under the garage roller doors. As I was putting the car away last night, I got the wife to unscrew the antenna. I still had the radio switched on, and the squelch turned all the way down, o I could still hear the interference. When she took the antenna off, the interference practically halved! What does this suggest? CKL > try the ferrite bead idea > [quoted text clipped - 30 lines] > > > > > > Mike Harding > If I use ferrite beads, don't I have to find out what frequency the > interference is? How do I do that with a piece of string, a paper clip, and > a peanut? (That's about all the specialist equipment I have!) :-) Don't worry about the freq, just get a ferrite bead (or donut, depending on what school you went to) and wind the cable through it as many times as it will fit. The number of turns will depend on how tight the (nun's) hole is! Do the same with the power lead at the radio end of the lead and get a good clean connection to the battery. One trick is to use a length of coax cable as the power lead. You may have better luck if you only connect the outside conductor to earth at only one end (you choose!) as this "MAY" assist. Note that this sounds like a health tonic disclaimer and in real life rather than the design lab sometimes works well. > The AM on my normal stereo does not have the interference. It's antenna cable would probably go through the guard (depending on type of car) and behind the dash. Maybe you can route the coax cable via the guard rather than the engine bay. Maybe it won't make any difference! > I have already > got the ANL switch on. It makes a huge difference to the noise level. I [quoted text clipped - 4 lines] > way down, o I could still hear the interference. When she took the antenna > off, the interference practically halved! What does this suggest? Do you have an earth strap on the bonnet? If not, add one! > CKL > > try the ferrite bead idea [quoted text clipped - 38 lines] > > > > > > > > Mike Harding > Do you have an earth strap on the bonnet? If not, add one! Will fixing a wire from the bonnet to the firewall do the job? If the connections are clean of paint etc it will be fine the firewalls a good earth generally. >> Do you have an earth strap on the bonnet? If not, add one! > > Will fixing a wire from the bonnet to the firewall do the job? I got the wife to unscrew the > antenna. I still had the radio switched on, and the squelch turned all the > way down, o I could still hear the interference. When she took the antenna > off, the interference practically halved! What does this suggest? > CKL It means the interference is coming through the antenna and cable what is the earch like at the antenna end?, does the antenna mount have a good contact with the bullbar and does the bullbar have a good earth contact with the body and does the body have a good earth contact with the "-" on the battery? with older cars lots of this type of interference could be fixed with a couple of condensors(capacitors)fitted to the distributor, coil and altinator, but with newer vehicles not having a distributor and coils at the sparkplug it's a bit harder to fix at the source with the ferrite beads you need to fit them at the radio end of the cables Kev > what is the earc(t)h like at the antenna end?, does the antenna mount have > a good contact with the bullbar > and does the bullbar have a good earth contact with the body I was thinking the same thing, if it were a ARB bullbar, which in most cases they are painted and when mounted to the chassis are mounted to a painted chassis, thus the paint is a great insulator against getting a good earth for the antenna or any other accessories you wish to mount on them and also mounted with cheap bolts that will most likely corrode or rust. > Kev Cheers Richard Although the bull bar is a chrome one, I can understand what you guys are talking about. I'll check out that option too. Thanks, CKL > > what is the earc(t)h like at the antenna end?, does the antenna mount have > > a good contact with the bullbar [quoted text clipped - 10 lines] > Cheers > Richard no go for it. > Just a thought before I start screwing around with this. If I leave the > antenna where it is, and re-route the antenna coax, will I bugger up the [quoted text clipped - 51 lines] >> > Please reply here with any help. Thanks. >> > CKL http://www.aulro.com/modules.php?name=Forums&file=viewtopic&t=3234 27meg/AM to become redundant by next year.. >http://www.aulro.com/modules.php?name=Forums&file=viewtopic&t=3234 >27meg/AM to become redundant by next year.. A link to a Brit forum on 4WD. Had you posted and asked what the Brits knew about 4WDing Biggus would have replied, "f.ck all!" - and (for a change) he would have been correct. Mike Harding Copy of relevant info from aus.radio.cb: "Yes, but the UK are losing 40 channels because until recently the UK used it's own HF CB channels which were different to ours (the US system) and used F3E. Since the UK joined the EU they have been required to change to American (seems to be standard) sets, using AM. IN the mean time (until 2010) a UK CBer can use his old FM set (or a new one with FM (F3E) and the old channel allocations) until 2010, after which time the UK will be only allowed to use the same 40 frequencies that the US and Australia use in AM (A3E) mode. It's on the UK equivalent of our ACA's website...so the UK isn't getting rid of 40 channels, but rather switching to the international CB standard (at least for western countries anyway) This can be found via the RSGB website" > >http://www.aulro.com/modules.php?name=Forums&file=viewtopic&t=3234 > >27meg/AM to become redundant by next year.. [quoted text clipped - 6 lines] > > Mike Harding > Copy of relevant info from aus.radio.cb: > "Yes, but the UK are losing 40 channels because until recently the UK used [quoted text clipped - 12 lines] > > This can be found via the RSGB website" The EU allocation does mirror the US and Australian 27Mhz channels, though FM is used. (It's certainly nicer). The Brits had their unique additional 40 channels, also using FM, starting above our own existing allocation (I have those frequencies listed somewhere). Brit CB's had typically a EU/UK band switch. This is all part of the EU harmonisation. You can phone the European Union Radio Office in Denmark for information. JP. http://www.outerlimits4x4.com/PHP_Modules/phpBB2/viewtopic.php?t=33201 Bull by the Tale in a big way. I know a lot about this topic (Closer to home than the average pay cheque) and just because it has been approved by the FCC (US Radiocommunications agency) doesn't mean it will be allowed hear without any forthought. Triaqls have been run - and are continuing to run on the use of BPL (Broadband PowerLine) and to be honmest the copst to instigate such a system is not just a matter of launching the info onto the line. There is serious amounts of attenuation over short distances - hence needing repeaters very regularly. The main effect will be on HF communications but the AM 27 MHz radio is a class licensed system (CBRS - Signed in 2002 - http://internet.aca.gov.au/acainterwr/aca_home/legislation/radcomm/class_licence s/cbrs.rtf) and I don't think this will be revoked any time soon. I would be more concerned about true HF over the horizon radios not the 27 MHz units - and only when the annmouncement to allow these BPL's in happens. BTW there will NOT be a blanket allowance of these systems but an allowed level of radiation that will reduce the noise floor of other devices in the very near vaccinity (talking parked underneath the powerline in an 8 inch lifted truck sitting on 44's on the back of a tilt tray......) I bet more of the panic merchants don't even know that channel 22 and 23 UHF 477 MHz are allocated for Telemetry use only - Quote: (g) must operate on a duty cycle of not more than 3 seconds in any period of 60 minutes; and (h) must be fitted with a device that shuts the transmitter down after 3 minutes of continuous operation. Operation contrary to this is not in accordance with the class licence - hence not legal - Now how many club radio channels are UHF22 or UHF23.... Heard the same rumours, but that's all they were. There is no truth to them. Been discussed to death and proven false on aus.radio.cb CKL > http://www.aulro.com/modules.php?name=Forums&file=viewtopic&t=3234 > 27meg/AM to become redundant by next year.. i just can't help but ask if anyhting has ever been proven in any sense of the word on aus.radio.cb > Heard the same rumours, but that's all they were. There is no truth to them. > Been discussed to death and proven false on aus.radio.cb > CKL > > http://www.aulro.com/modules.php?name=Forums&file=viewtopic&t=3234 > > 27meg/AM to become redundant by next year.. > Hi all! I have just installed an AM only CB in my NJ Pajero. Please don't > ask "Why?" You will not get a response! I am only looking for helpful, [quoted text clipped - 16 lines] > Please reply here with any help. Thanks. > CKL Interference and petrol motors with AM receivers go hand in hand. The easy way out is to buy a diesel that doesn't have common rail injection. Failing that there's a multiplicity of things that can be tried. At best some of them may reduce your noise level.but non can be guarenteed to cure the problem. The whole process can take a lot of time and effort, and different cb radios may have different levels of interference in the same vehicle. Even the aerial position can have an effect. The petrol engine is a "wide band radio transmitter" by itself. The minimizing noise process can be thought of as having two parts. The installation and The vehicle Poor design or alignment of radios can affect their ability to respond to interference. Same with the vehicle. There have been some good posts (eg ferrite rings ...they have frequency bands so get the right ones) etc. Mechanical bonding of all chassis and cab components (dont forget the exhaust pipe etc) can help. Bypass caps and shielded wires etc can help, as can some noise filters. Do a Google and you'll see what I mean. Good luck. Cheers Jim OK, Went to DSE today, and they told me they don't sell the in-line noise filters anymore, but all they did have was ferrite cores. Only $3 each so I bought 2 of them. Put one on the antenna coax, at the radio end. No difference. Put the other on the power lead, again, at the radio end, with the power cable passing through it 3 times. (couldn't fit it through any more than that.) Still no real difference. Still showing 2 signal lights at idle, with the 2nd one now flickering from time to time, so perhaps it has reduced it a smidgen, but not noticeably. I've left them on, as I guess they won't hurt anything. The DSE guy told me that if it didn't help, then a car accessories place should have something to go across the alternator. I am beginning to think that my problem might be more alternator noise now. Don't ask me why, just leaning that way. And so we continue! CKL > > Hi all! I have just installed an AM only CB in my NJ Pajero. Please don't > > ask "Why?" You will not get a response! I am only looking for helpful, [quoted text clipped - 46 lines] > Cheers > Jim You can always drop the fan belt off to see whether the interference is coming from alternator or elsewhere I am bit sus that you may have an earth loop - just for fun disconnect the antenna mount from earth - eg the ant co-ax shield only earthed at the radio end, not at the bull bar etc - see if that changes things David PS If all else fails go and have a nice chat with one of the car radio installation guys - they should have lots of clues > OK, Went to DSE today, and they told me they don't sell the in-line noise > filters anymore, but all they did have was ferrite cores. Only $3 each so I [quoted text clipped - 71 lines] > > Cheers > > Jim Not real keen on dropping the fan belt off, for simple fear of not being able to put it back on and tension it right myself. I will do as you suggest and disconnect the antenna mount from earth, and see if that does anything. If it makes it better, what does that mean, and what is the solution? As far as the car radio installation guys go, every place I spoke to in Geelong about checking the SWR told me to go to Len Day Car Radio, so I went there, and they did the SWR for me, ($25), but when I asked, on 2 occasions, about the interference, they told me there was nothing at all that could be done. I suspect they just don't want to be bothered with an 'old fashioned' AM radio any more than they have to. I am hoping to be able to find a solution myself, by following the advice that you guys here give me, but if all else fails, I was thinking of taking it to an auto electrician maybe? CKL > You can always drop the fan belt off to see whether the interference is coming > from alternator or elsewhere [quoted text clipped - 83 lines] > > > Cheers > > > Jim Im curious, ive used plenty of AM radios and now run a TX3200 UHF, the SWR was around the 2.1:1 with the standard setup, I tuned the system to 1.4:1 and got a fairly good range increase. (not sure if the cloud cover contributed to that or not once the job was done) Anyone had bad experiences with UHF radios and poor SWR? > Not real keen on dropping the fan belt off, for simple fear of not being > able to put it back on and tension it right myself. [quoted text clipped - 135 lines] >> > > Cheers >> > > Jim > Im curious, ive used plenty of AM radios and now run a TX3200 UHF, the SWR > was around the 2.1:1 with the standard setup, I tuned the system to 1.4:1 > and got a fairly good range increase. (not sure if the cloud cover > contributed to that or not once the job was done) > > Anyone had bad experiences with UHF radios and poor SWR? Most UHF radios on the market today have VSWR protection that will reduce the power output of the radio when the SWR is high unlike the old days of the AM 27Mhz radios that had no protection and in most cases the power would increase with bad SWR and would eventually cause the radios final driver to sizzle. Cheers Richard > Not real keen on dropping the fan belt off, for simple fear of not being > able to put it back on and tension it right myself. [quoted text clipped - 15 lines] > all else fails, I was thinking of taking it to an auto electrician maybe? > CKL Hearing how keen you are to get this all up and working properly almost makes me want to get my very old (almost vintage) radio out of moth balls and jump back on the band to have a little play around and see what old timers (like myself) I still recognise on there. I would think that with the innovation of UHF CB and specially those cheap ones that it should be fairly quite on there and you shouldn't have a problem with getting a little privacy unlike UHF radio. BTW - I came across this little file on the Barrett web site which is supplied with their Suppressor Kits that might be of a little assistance to you in figuring out what the sounds are your hearing and hopefully give you a little insight to your problem. http://www.barrettcommunications.com.au/pdf-files/INSTALLATION%20GUIDES/suppres- kit-in-BCM99017-2.pdf Cheers Richard >Hearing how keen you are to get this all up and working properly almost >makes me want to get my very old (almost vintage) radio out of moth balls >and jump back on the band to have a little play around and see what old >timers (like myself) I still recognise on there. Good idea Richard. I'm a, sort of, new time CBer - but I have a set in the vehicle which cover AM CB (SSB and AM) and 10/12m Amateur Bands. Bugger! Guess that's an illegal radio too! :) I'll keep an ear open on chan 16 or 35 USB, last time I was there I used the callsign EB2000 (echo bravo two thousand) - maybe we'll meet up? Mike Harding >>Hearing how keen you are to get this all up and working properly almost >>makes me want to get my very old (almost vintage) radio out of moth balls [quoted text clipped - 6 lines] > which cover AM CB (SSB and AM) and 10/12m Amateur > Bands. Bugger! Guess that's an illegal radio too! :) ILLEGAL, no those switches do exactly what they say on the front of my ole radio, my biggest problem would be remembering what they all did :) > Mike Harding Cheers Richard Thanks for the file! After reading it, I think I may have more than one source of interference. I know that the windscreen wipers create a whine through the radio, as does the fuel pump, however, I run 95% of the time on LPG, so that's not a real concern. I think I might have to get some RG58 coax to use as the power lead and see if that helps. In that case, what do I do about the fuse? I noticed yesterday, when my son flicked on the spotlights switch, that that also made rather severe interference in the radio. ( That was until of course, I disconnected the switch, and noticed the switch itself was a bit melted. Hooking it up again saw the 3 wires attached to it heat up with incredible speed and melt the insulation, leaving a lovely smell in the cabin and my nostrils! But that's a separate problem!) You are right about the AM CB band being quiet. I live in a small town that doesn't even have a mail delivery service to the houses, so there aren't many people around. In Geelong however, I can often hear people having a chat. Some of them are obviously drop kicks mucking around, but I have heard quite a few 'normal' conversations, as well as a few convoy type groups. I haven't bothered to join them as yet due to my interference. CKL > > Not real keen on dropping the fan belt off, for simple fear of not being > > able to put it back on and tension it right myself. [quoted text clipped - 29 lines] > you in figuring out what the sounds are your hearing and hopefully give you > a little insight to your problem. http://www.barrettcommunications.com.au/pdf-files/INSTALLATION%20GUIDES/suppres- kit-in-BCM99017-2.pdf > Cheers > Richard > Thanks for the file! After reading it, I think I may have more than one > source of interference. I know that the windscreen wipers create a whine [quoted text clipped - 11 lines] > incredible speed and melt the insulation, leaving a lovely smell in the > cabin and my nostrils! But that's a separate problem!) ---SNIP--- > CKL I have an opinion on the matter of running such a long length of earth (-) wire from the radio to the battery (which a few might flame me for). This was a great idea in the old days prior to the 80's when vehicles still had points and carburettors with manual chokes and CB radios were crystal controlled, but in the modern era I don't think this works very well. EFI, Computers and the like produce a lot of interference for radio and audio equipment. In most audio installations it is highly recommended that the earth/negative (-) wires be kept as short as possible and as close to the source as possible and that all wires are to be kept the same dimensions or greater than the original size. Personally I would earth the CB radio as near to the back of the radio as possible. The reason for not running the earth to the battery is that most inherited noises come in through the earth first and there will already be other sources getting their earth from the battery and you could be inheriting the noise from these other sources. An old trick not mentioned much anymore is to keep your radio and the earth point low in the vehicle. Equipment mounted up high like in roof consoles or the top of your dashboard also tend to pick up noise because their not surrounded by as much metal. Another source for creating noise is wires that are not properly terminated or joined. If you have any wires that are just twisted together and held together with electrical tape this could cause interference too. Always terminate wires with crimps and join wires with solder. Also try and keep the coaxial cable away from the power lead of the CB. Run them down opposite sides of the car. The antenna is all the way out there in the front of the vehicle and only finding its earth starts at the bullbar. Its a great source for picking up noise being in front of the car. I have seen many people beat themselves up over your same problems, but in the end it usually ends up being something simple. Good Luck Cheers Richard Thanks for that. I do now have the coax and the power cables running down opposite sides of the vehicle. Since doing this, and spending too many nights laying awake at night trying to figure this out, I have been left with a question. As the normal car stereo does not give any interference when listening to AM, I assume this is because the antenna goes through the fire wall, and then immediately out into the guard. If I route my coax through the same way, and thusly around all the electricdal stuff, should this help eliminate interference, or would I just be wasting 1/2 an hour? CKL > > Thanks for the file! After reading it, I think I may have more than one > > source of interference. I know that the windscreen wipers create a whine [quoted text clipped - 52 lines] > Cheers > Richard Definately worth doing Id say. Dont forget that the stereo antenna is smaller than the CB sets one so will not pick as much interference. As an excersise remove the stereo aerial plug and use (hooking up with tempory connections) as CB antenna, if all interference goes Id say its a coax or aerial issue. > Thanks for that. > I do now have the coax and the power cables running down opposite sides of [quoted text clipped - 83 lines] >> Cheers >> Richard OK, today I disconnected the earth from the coax, and started the engine. Normally, the cb would show 2 out of 4 signal strength lights at this stage. With the earth disconnected, it showed none, with just one flicking on intermittently. (in line with increased interference that's floating around.) What does this suggest? I also fed the coax through the fender, rather than through the engine bay. With the coax earth connected at the antenna, I now get only one light at idle, with the second one flickering intermittently, and 2 full lights on acceleration, and high revs. I also moved the negative wire to the dash metal, from the engine bay, making it only about 12cm long now. My opinion is that with the coax earth connected, and the changes I've made with the coax routing, it's made SOME difference, but not as much as I was hoping for. With the coax earth DISCONNECTED, it seems to have made more difference. What problems are associated with using the unit with the coax earth disconnected? and what is the reason, and therefore solution for this? I have not yet attached a wire from the bonnet to the fire wall, simply because I couldn't see a suitable place today when I looked. Looks like we might be finally making some headway! > Not real keen on dropping the fan belt off, for simple fear of not being > able to put it back on and tension it right myself. [quoted text clipped - 122 lines] > > > > Cheers > > > > Jim Keep us posted eh, sounds like your getting there. Wondering if you have a floating earth set up....... > OK, today I disconnected the earth from the coax, and started the engine. > Normally, the cb would show 2 out of 4 signal strength lights at this [quoted text clipped - 173 lines] >> > > > Cheers >> > > > Jim No, I don't have a floating earth, but I was told by a guy that does marine electronics that I should. Are you suggesting it would also help? CKL > Keep us posted eh, sounds like your getting there. Wondering if you have a > floating earth set up....... [quoted text clipped - 176 lines] > >> > > > Cheers > >> > > > Jim Whats the reception like when earth dissconected also TX. > OK, today I disconnected the earth from the coax, and started the engine. > Normally, the cb would show 2 out of 4 signal strength lights at this [quoted text clipped - 173 lines] >> > > > Cheers >> > > > Jim I wasn't sure if I was doing any damage with the coax earth disconnected, soi IU didn't muck around with it much like that. Now I know it won't hurt anything, I'll have a bit more of a play this week, and let you know. Fact of tjhe matter is that I've not yet actually used the unit to speak to anyone yet. Just been too busy trying to sort out this interference. I tried yesterday when I had the earth disconnected, and I could hear a guy whistling, but he never answered me. Trouble is that where I live, there's never any people around. Have to wait until my lunch break when I'm in town, and we'll see what happens. Would be a major pain in the a.s if it turns out I'm not even transmitting! :-) I'm sure I am. CKL > Whats the reception like when earth dissconected also TX. > [quoted text clipped - 175 lines] > >> > > > Cheers > >> > > > Jim Finally found a couple of guys on air that confirmed I am actually transmitting clearly, even with the engine running, so it seems the RX quality is the only major issue with the unit. CKL > I wasn't sure if I was doing any damage with the coax earth disconnected, > soi IU didn't muck around with it much like that. Now I know it won't hurt [quoted text clipped - 214 lines] > > >> > > > Cheers > > >> > > > Jim Well, assuming you were not actually gettinga signal from another CB, the signal lights going off means that your interference had dropped my a large margin. When I suggested you might have an earth loop, what I meant was that by having the co-ax sheild connected to earth at two points (the set and the antenna) this set up a loop which allowed interference to raise its ugly head. The co-ax sheild will be earthed at the set. So if not earthing at the antenna helped then leave it that way. David > OK, today I disconnected the earth from the coax, and started the engine. > Normally, the cb would show 2 out of 4 signal strength lights at this stage. > With the earth disconnected, it showed none, with just one flicking on > intermittently. (in line with increased interference that's floating > around.) What does this suggest? After driving to work this morning, I noticed that a LOT of the 'popping' has gone, and I can now mostly hear a 'sssshhhhhhhhh' type static, and 2 signal lights on whilst driving. I noticed that when I put my foot down, the sssssshhhhhh quietens down, and returns when I release my foot. I'll see if it's better with the coax earth disconnected as you suggest. I got rid of all lights yesterday, but I did notice one light came on after about 5 seconds. We'll see how things are after leaving the earth disconnected, and if it's much improved, I think I'll call it as good enough! 3 bloody weeks of screwing around for a $12.50 cb!! LOL! I need to get out more! :-) CKL > Well, assuming you were not actually gettinga signal from another CB, the > signal lights going off means that your interference had dropped my a large [quoted text clipped - 14 lines] > > intermittently. (in line with increased interference that's floating > > around.) What does this suggest? > After driving to work this morning, I noticed that a LOT of the 'popping' > has gone, and I can now mostly hear a 'sssshhhhhhhhh' type static, and 2 [quoted text clipped - 9 lines] > of screwing around for a $12.50 cb!! LOL! I need to get out more! :-) > CKL That COAX, (with the centre conductor acting as supply) what type?? 50ohm etc... I am thinking of trying a length of quad shield 75ohm when next I do the 27Mhz bit. Additional shielding over most.... It's just normal RG58 coax. CKL > > After driving to work this morning, I noticed that a LOT of the 'popping' > > has gone, and I can now mostly hear a 'sssshhhhhhhhh' type static, and 2 [quoted text clipped - 17 lines] > > Additional shielding over most.... Why not just fork out for a UHF set and be done with it! > After driving to work this morning, I noticed that a LOT of the 'popping' > has gone, and I can now mostly hear a 'sssshhhhhhhhh' type static, and 2 [quoted text clipped - 34 lines] >> > intermittently. (in line with increased interference that's floating >> > around.) What does this suggest? This is what someone else has said to me thius morning about disconnecting the coax earth. Is there any truth to it? If you disconnect the coax earth at the antenna end the whole antenna system is likely not working well any more. If you were to measure VSWR for example it would probably be way out.. The drop in noise level would be a drop in antenna performance. CKL > Well, assuming you were not actually gettinga signal from another CB, the > signal lights going off means that your interference had dropped my a large [quoted text clipped - 14 lines] > > intermittently. (in line with increased interference that's floating > > around.) What does this suggest? Highly likely. > This is what someone else has said to me thius morning about disconnecting > the coax earth. Is there any truth to it? [quoted text clipped - 29 lines] >> > intermittently. (in line with increased interference that's floating >> > around.) What does this suggest? this correct you VSWR will be way off and there is the potential of burning out the finals in the radio($12.50 is $12.50 + the money you spent having the antenna tuned) you antenna will not work any where near as well (turns you antenna into an attenuator) connect the antenna earth back up from what you have been saying it appears the noise is getting in from the antenna I think maybe moving the antanna to the rear of the vehicle will probably solve the noise issue try something different try fixing it at the source a bit of shielding around the coil packs on the engine this noise issue may also mean there could be a damaged plug lead, dirty plug lead connections anywhere that a spark is being created other than the spark plug gap Kev > This is what someone else has said to me thius morning about disconnecting > the coax earth. Is there any truth to it? [quoted text clipped - 29 lines] > > > intermittently. (in line with increased interference that's floating > > > around.) What does this suggest? If I move the antenna anywhere else other then where it is now, will that muck up the SWR? The only place on the back of the Pajero would be from behind the spare tyre. Wouldn't this cause other problems? Dirty plug lead connections and the other things you suggested could be an idea. I do travel on dusty gravel roads almost every day, and a mechanic hasn't been anywhere near the engine for about 35,000km. (I change the oil myself, and it has platinum plugs!) It's a shame you can't just buy shielding to wrap the coax in! (or can you buy it?) Where would I get shielding for the coil pack from? CKL > this correct > you VSWR will be way off and there is the potential of burning out the [quoted text clipped - 52 lines] > > > > intermittently. (in line with increased interference that's floating > > > > around.) What does this suggest? moving the antenna will have some affect on the VSWR but nothing that will be too dramatic (and instead of paying someone to retune the antenna, look about your area for a CBer or Amateur operator, chances are they will have a VSWR meter and can check it for you) if you make a bracket that comes up behind the spare wheel and mounts the antenna just clear of the tyre it will work fine funny things these antennas, what will happen is you may find that your radiation pattern will change and you might get better reception from the front of your vehicle than before with the antenna mounted on the bullbar whan it's on the bullbar your signal path would favour a rearwards direction it has to do with groundplane, you get better signals in the direction of the most groundplane Shielding it can be made from any electrically conductive material, anything really, wrapping the cable in alfoil will work fine(some coax cables use this) the coil packs can be wrapped in foil(though heat may be an issue with no airflow), or even metal gauze(fly screen type, but must be metal) make up a mesh box that covers the coil packs with holes for the plug leads and other wiring as long as it's earthed to the car body it will act as a screen it's proper name is a "Faraday's Cage" Kev > If I move the antenna anywhere else other then where it is now, will that > muck up the SWR? [quoted text clipped - 9 lines] > Where would I get shielding for the coil pack from? > CKL OK then. This is starting to sound like it should work! I might try and wrap the coax in alfoil and see if this makes any difference. (have to try and sneak it out of the kitchen without the wife seeing it! ) As far as the metal wiring goes, the electrics on the Paj are all under a mountain of covers. Would a barrier made of the metal flywire material placed between the coax and the electrics serve the same purpose? , or I guess, wrapping the coax in the maetal flywire even? Looks like I may need to source an old SWR meter from somewhere. I've been told it's easier than getting pissed in a brewery to do it yourself. CKL > moving the antenna will have some affect on the VSWR but nothing that > will be too dramatic (and instead of paying someone to retune the [quoted text clipped - 38 lines] > > Where would I get shielding for the coil pack from? > > CKL Were are you located? > OK then. This is starting to sound like it should work! I might try and > wrap [quoted text clipped - 55 lines] >> > Where would I get shielding for the coil pack from? >> > CKL Indented Head Victoria. (30 min from Geelong) > Were are you located? > [quoted text clipped - 57 lines] > >> > Where would I get shielding for the coil pack from? > >> > CKL Kev, perhaps you could elaborate as to why it is necessary to earth the antenna lead shield at both ends - buggered if I can think of any technical reason why this should affect swr, so??? David > this correct > you VSWR will be way off and there is the potential of burning out the [quoted text clipped - 52 lines] > > > > intermittently. (in line with increased interference that's floating > > > > around.) What does this suggest? All changes will affect the VSWR to some degree the coax outer shielding is not just to shield the centre conductor but also forms part of an unbalanced feedline removing the earth at the antenna turns it into a longwire antenna that starts at the radio and not the antenna mount this will then be non resonant for the freqs being used and a mismatch occurs and you would then need an antenna matcher this type of antenna will always need a radiating element and a ground plane to work properly Kev > Kev, perhaps you could elaborate as to why it is necessary to earth > the antenna lead shield at both ends - buggered if I can think of any [quoted text clipped - 81 lines] > > floating > > > > > around.) What does this suggest? >Interference and petrol motors with AM receivers go hand in hand. The easy >way out is to buy a diesel that doesn't have common rail injection. Jim, how does common rail injection differ from other diesel engines (in terms of radio interferance)? Cheers Craig there is a fuel rail that is pressurized at a constant rate and equal at all injectors, the injectors are then fired electronically as needed, so you get a burst of current every time an injector fires/opens Kev > >Interference and petrol motors with AM receivers go hand in hand. The easy > >way out is to buy a diesel that doesn't have common rail injection. [quoted text clipped - 4 lines] > Cheers > Craig >there is a fuel rail that is pressurized at a constant rate and equal at >all injectors, the injectors are then fired electronically as needed, so >you get a burst of current every time an injector fires/opens > >Kev Ahh, Ok. Is it a significant source of interferance, say compared to a standard petrol engine. I'm currently driving a 4.2 GQ and am planning on upgrading to a GU 3.0 diesel patrol, and was hoping switching to diesel would get rid of the nagging interference on my UHF cb. Do all methods of injection cause the same affect? >> >Interference and petrol motors with AM receivers go hand in hand. The easy >> >way out is to buy a diesel that doesn't have common rail injection. [quoted text clipped - 4 lines] >> Cheers >> Craig |
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