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Creating a RF choke...on purpose?
- Thread starter Freightlinerbob
- Start date
Well yes Bob's is probably a good place, but Bob has little time for questions and he seems to be the only one there that knows anything. His "antenna guy" was pretty much suggesting to me to change everything but the radio. At one point he said "maybe it because you're running power" .
Well no s**t Sherlock, i just told you that the dash only cycles when using the amp. That's why I'm here!
One doesn't have to know anything about radios (that's me) to know that you should go from the easiest to the hardest and methodically chart your progress when trying to diagnose anything.
I had to ask the antenna guy if there was a better coax to use, he said yes- double shielded, but I then had to ask again if they had a test piece I could try before buying. So we hung a piece through the window. At my suggestion!!
After seeing some success with the coax, I bought a pre made piece and left. Asking more questions there would have gotten me nowhere and pissed off the only one who knew anything, and had little time for questions, because he was literally fixing radios one after another.
As a side note, they advocate using 18' of coax. I'm just throwing that out there because many other reputable people say otherwise. I have no opinion on the matter because I don't know anything. My point is that getting good info is pretty hard even at a good shop and then it could very well conflict with another good source.
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If the radio is throwing off excessive harmonics; then the amp will just amplify them. This condition might end up give off the right harmonic to interfere with your gauges. Eliminating the harmonics with a Low Pass Filter would mean that only a narrower band of harmonics could get amplified. I think I would try a LPF between the amp & radio. You know; beg, borrow, but not steal. If using that LPF helped a lot after testing it; then I would also put another LPF after the amp as well. Be worth buying some then - after seeing if it helped or not first. Won't affect the radio's perceived performance; just clears/filters out what isn't needed anyway. If that works; then the radio is not properly tuned or had the trap filter disabled. Or both. If you can borrow a LPF and a jumper coax to test out this possibility; I would.
Some guys ideas of tuning and peaking a radio include disabling the 54mhz trap coils to see the radio swing more. Very poor juju/medicine. Just increases the harmonic content being let out of the radio. I know of some techs with a high reputation that still use this practice. If you take the cover off of your radio and see those large copper coils in the back of the radio near the antenna connector - spread wide; then just push them back together. Just that easy to correct. If the same tech also re-tuned that upright bakelite tuning coil in that circuit incorrectly; then it can also cause too many harmonics leaking out of the radio. After all, VERY few radio techs/hobbists have their own Spectrum Analyzer to adjust or even observe the 54mhz trap output and bring it back into specs. I don't either.
I would also use a piece of braided copper wire from the amp chassis directly to the frame in the shortest path as well. This would dump all loose RF where it belongs - IMO . . .
The real problem just may be a total lack of RF blocking in the design of your tractor's electrical system. Which I think is odd - knowing that a trucker is going to use/or possible use a CB radio with an amp. Think I would also talk to the shop guys that work on these tractors and find out what they have to do to cure this problem. Surely you aren't the first guy to have this problem; and you won't be the last either.
Some guys ideas of tuning and peaking a radio include disabling the 54mhz trap coils to see the radio swing more. Very poor juju/medicine. Just increases the harmonic content being let out of the radio. I know of some techs with a high reputation that still use this practice. If you take the cover off of your radio and see those large copper coils in the back of the radio near the antenna connector - spread wide; then just push them back together. Just that easy to correct. If the same tech also re-tuned that upright bakelite tuning coil in that circuit incorrectly; then it can also cause too many harmonics leaking out of the radio. After all, VERY few radio techs/hobbists have their own Spectrum Analyzer to adjust or even observe the 54mhz trap output and bring it back into specs. I don't either.
I would also use a piece of braided copper wire from the amp chassis directly to the frame in the shortest path as well. This would dump all loose RF where it belongs - IMO . . .
The real problem just may be a total lack of RF blocking in the design of your tractor's electrical system. Which I think is odd - knowing that a trucker is going to use/or possible use a CB radio with an amp. Think I would also talk to the shop guys that work on these tractors and find out what they have to do to cure this problem. Surely you aren't the first guy to have this problem; and you won't be the last either.
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Hard to tell from the small pic on my phone, but it looks like a Columbia in your avatar.
I just got off the phone with a friend who has been fighting RF issues in a Columbia. He has two antennas on the truck, but only uses one. He switched from using the drivers side antenna to the passenger side and the issues went away. He swapped the actual antennas around to see if it was just the antenna causing it.(????) No change. If he uses any antenna on the drivers side mirror he gets RF problems. He's thinking there has to be something in the wiring that runs out to that mirror that picks up the RF.
He runs a 2950DX into a Texas Star Dx500v.
Good luck with it.
I just got off the phone with a friend who has been fighting RF issues in a Columbia. He has two antennas on the truck, but only uses one. He switched from using the drivers side antenna to the passenger side and the issues went away. He swapped the actual antennas around to see if it was just the antenna causing it.(????) No change. If he uses any antenna on the drivers side mirror he gets RF problems. He's thinking there has to be something in the wiring that runs out to that mirror that picks up the RF.
He runs a 2950DX into a Texas Star Dx500v.
Good luck with it.
Thanks to all the responses thus far.
I've actually been wondering about running the antenna on the passenger side since there are no gauges there and the main harness from the engine enters through the firewall right near the clutch pedal- exactly where the coax enters the cab from the door and travels up the "A" pillar.
The main reason to have the antenna on the drivers side is to avoid tree branches. I suppose it could go from the mirror bracket directly into the roof cap since the passenger door rarely gets used. This would keep the coax at the same physical level as the antenna mount and several feet away from any sensitive wiring. This would also leave plenty of cable left over to make an RF choke.
But that will have to wait as I'm heading to Fort McMurray right now and it's about -20 Celsius. I'm not working outside any more than I have to. BRRR.
I've actually been wondering about running the antenna on the passenger side since there are no gauges there and the main harness from the engine enters through the firewall right near the clutch pedal- exactly where the coax enters the cab from the door and travels up the "A" pillar.
The main reason to have the antenna on the drivers side is to avoid tree branches. I suppose it could go from the mirror bracket directly into the roof cap since the passenger door rarely gets used. This would keep the coax at the same physical level as the antenna mount and several feet away from any sensitive wiring. This would also leave plenty of cable left over to make an RF choke.
But that will have to wait as I'm heading to Fort McMurray right now and it's about -20 Celsius. I'm not working outside any more than I have to. BRRR.
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