Help: J&M garble-de-gook

[scherminator]

Got a question for any experienced J&M users or EE's:

Installed a J&M 2003 CB unit last season for a trip to the left coast with my brother in law (on a connie), and it works well as long as the revs on my bike are low. Ie., if we're at a standstill, we can chat with perfect clarity. As soon as we are tooling along though, it seems that the RF on my machine makes both reception and x-mit from my bike very garbled, almost like trying to hear voices over a roaring wind (but it isn't wind noise, because if I pull in the clutch and let the bike idle at speed, the reception becomes crystal clear). The interference is very clearly linked directly to my engine's RPM.

I have tried 2 different firestik NGP antennas and coax (36" european whip, and a regular 36" Firestik II), and have carefully routed the NGP coax away from other looms, and without looping it. I have a regular ground plane antenna which I can try, but I'm looking for input into things I have overlooked... I don't believe it to be the antenna. I have played with + adjusted the SWR with both antenna setups, and have got decent results (1.9 or so on 1 and 40, and 1.4 on 20).

Power is run to the unit directly from the battery (no relay), so it can be powered without the ignition on.

Weather radio reception is fine at all speeds/rpm, as is the aux input, although I did install an RF filter on the auxilliary input to kill the ignition noise that was only mildly present, but annoying. It is only the CB portion that is affected.

What have I missed? What should I be looking for?

Any help appreciated.

Kent

[Mellow]

Kent, I belive the J&M CB ships with a power noise filter... is it possible that is bad? I don't know much about the or if they can be bad but you might try to see if J&M will send you another one... I had one on my ST13 last year sometime and it never had the symptoms you mention. I did have a very faint alternator whine but it was so low it didn't bother me. It definitely sounds like alternator whine.

[scherminator]

Thanks for the reply. Yes, there is a noise filter in the power line. Is it possible to test it in-situ?

[Mellow]

I have no idea how to test one... maybe take it out if possible and see if there is a difference in how the CB acts. If it does the same with or without it, maybe it's not doing it's job.

[scherminator]

Well, I just tried RC's advice and went with another noise filter in the power line. No joy, same problem.

Well, I'll try the ground plane antenna next. In the meantime, if anyone has any ideas please chime in...

^$#*# (Kent, garbled)

[CruisingDog]

It sounds like you are getting a load of EFI (electronic fuel injection) noise through the power or ground cables. There are a few ways this can happen:

1) directly injected through the power or ground. To solve this you need to get an RF-choke and put it in the power or ground or get a common-mode choke and put this in the power & ground. (this filters both ground and power at the same time). Caution: Your antenna ground must be after the choke (ie on the radio/cb side of things). Probably not an issue since you'll have a seperate co-ax cable.

2) You are getting EFI noise coupling into the antenna. Possible solution is have a second shield arounf the co-ax cable and bond it to the chassis ground.

3) You are getting noise coupling into the radio set. Bond the radio to chassis ground with a good multi cored wire.

4) You are getting spark noise. Try a spark-arrestor in the power and/or antenna. This might remove the high frequency crap in the airwaves.

5) Your power cables are badly layed out. Try twisting them and running them close to the metal fram (chassis). Twisting cancels E/H fields since every twist is anti-phase with the last twist.

Anyway, there's some thoughts for you. Hope they help you isolate the problem.

[duSTy]

You probably already did this, but disconnect the aux input if you are using one. I had to put in a ground isolator between the J&M and my XM. Also make sure you route your wires right down the center of the gas tank. I had noise problems when I put things on the left side of the bike.

Also, where are getting your power from?

Tom

[Dorian]

All you JMCB-2003 users, I would also like to know where you elected to take your power from.

[Mellow]

All you JMCB-2003 users, I would also like to know where you elected to take your power from.

Dorian, when I had mine I pulled power from the rear running light but that's just because I was too lazy to take the plastic off to get to switched power in the harness.

[crazykz]

I've read through some of this but disconnect the aux input. If you're using that you're going to have to isolate that input. Electrical Connections sells one that you can drop right in that has 1/8" stereo M to F connectors.

Two, you have the exact issue I had when I pinched a cable and injected RF from the shield of the cable into the signal line on the cable and I have GLI's all over the place to eliminate the spark plug ticking or EFI ticking. Not saying you have a pinched cable but you are picking up the same RF I was picking up because my cables run between the airbox and the frame to get up to the handlebars which means going near the coils even though they are on the outside of the frame.

I guess look for pinched wires and also consider grounding the shield of the cable to bike ground to try and pull any RF to ground. Right now even with a good shielded cable the RF you pick up is probably going to end up in the CB if it doesn't have a way to shun it to ground. You could try something as simple as wrapping some copper wire around the outside of the connector for the antenna (if it is connected to the shield) and then running the wire to a ground point somewhere.

Just a suggestion. I'm really pulling this out of my *** to try and give you something that might help find the issue.

I know Brett Donahue is having a similar issue but he's picking it up from his heattroller setup.

I use the N-500 from www.davidnavone.com ($17) to clean up the power source but in your case I'm not sure that's what you need.

Curt

[Rob Hephner]

Power is not the issue for noise, never is. As a professional in the Mobile Electronics Industry I have a great depth of knowledge in this area (Ask David Navonne, he knows me personally). The "noise" filters that you guys get sold are really only a band-aid to fix bad isolation and do not really get rid of the noise as much as they reduce power to do so, in any event let me take you through a process to get rid of the engine noise.

First of all, where did you ground the main power unit? My suggestion would be to not go all the way back to the battery, in fact find a spot on the frame near the unit to attach.If the unit is in the left pocket I would suggest that you attach the ground under one of the bolts that attach the farring support rails (black) to the frame. Do you follow me?

I have my XM unit grounded there with zero noise issues.

[Fireball18]

Both my wife and I have the JMCB units on our ST's and we love them. So far no problems, and both transmission and reception have been very clear. I did have one occasion in which I noticed some pretty loud ignition noise with the CB. Sounded like someone firing a machine gun. Anyway, I pulled the left side fairing loose and found that both my antenna and power leads were resting on the ignition coil. I lifted them off and repositioned them below the coil and since then no noise.

Make sure you don't hook up to the battery for ground or your hot lead. I wired into the taillight for power and connected the ground lead directly to the frame. I routed the power and antenna wires down from the handlebar, along the left frame rail (making sure they didn't come close to the ignition coil) and up, under the seat next to the frame. I ran the wires down through the area where your owner's manual sits, and directly below I drilled a small hole in the plastic and ran the power lead through it so I could connect to the taillight power wire. I used one of the chromed bolts on the seat support rail for my ground.

I currently have the antenna that comes with the kit, but I'm not wild about it, as it doesn't provide for very much range. I'm thinking about getting a CB antenna available at most of the larger truck stops, that has a brass screw in the top of it for easy adjustment of the SWR. Once you start cutting the wires in the stock antenna, you can't undo it if that's not the direction you needed to go.

When J&M is contacted, their stock answer for nearly all radio problems is "you need to properly tune your antenna." I don't agree. While I'm no electronics expert, I've been around and used electronics of different sorts over the years, and I can tell you, tuning the antenna doesn't solve anything but poor transmission or reception. If you're experiencing noisy reception, etc., it most likely is something drastically different. It could be in the wiring or it could be a defective radio unit itself. Good luck in tracking this down.

[ST090]

My experience with CB radios on both the ST1100 and ST1300 as well as other bikes is that a weak ground could be the problem so try using a frame ground rather than the battery post ground.

I don't have the theory for the next statement and it goes counter to what others may say but the battery, in my opinion, is not the place to take your power for a CB on the ST1300. I have always taken power from an auxilary switched source and had good results with 2 J&M 2003 CBs--one on a 2003 ST1300A and a second unit on a 2004 ST1300A.

These kind of issues will drive you crazy!

[Rob Hephner]

Fireball is on it.

You should not have an issue going directly to the battery for power, that is the only thing I would not agree with. The ground is very important. Never go to the battery.

[scherminator]

Thanks for the discussion and food for thought. For clarification, the unit is grounded to the frame. Based on some further suggestions from John at J&M I've tried sourcing the power from the tailight, and also grounded the antenna bracket to the same ground as the CB. These changes were made independently for testing. The power source made no difference. Grounding the bracket made a small improvement, but not enough to render the CB useable.

Ah well, I think I've exhausted just about every combination & permutation available to me... other than sacrificing some livestock and drinking chicken's blood.

On J&M's suggestion I'll be sending the unit back to them for testing.

[Rob Hephner]

And sometimes...the unit is bad.

[Fireball18]

I thought I'd pass this on FWIW. My father-in-law also has the JMCB unit and has been experiencing some audio problems. His was with the aux. audio, and the sound kept cutting out in the right earphone. We eventually tracked it down to the 9-pin power plug that was defective. The female part of the plug has 9 wires going into it, coming down from the radio unit in a wire bundle. What we found was that three of the brass prongs weren't seated in their slots properly, so when the male half of the plug was plugged in, it merely pushed these pins away and only made sporadic contact.

We contacted J&M and I asked for a technician who advised me that he had absolutely no idea what I was talking about. I then asked for a "real" technician who informed me of the same thing and merely stated I needed to pack it up and send it in for him to repair. Not to be put off, I determined to investigate further and solved the problem. All is crystal clear now.

You might want to check out that 9-pin plug and make sure all the contacts are properly seated and locked into their slots. There is a small locking tab that locks against a plastic tab inside the slot. There is also a 3-pin plug that bears checking out, as well. I don't know if this will help at all, but I just thought I'd toss it in for info.

[Bikerjoe]

Putting a J&M CB on and am not quite sure which wire (color/colors) going to tail light do I want to use for power? I will use the frame as ground as suggested. Thanks in advance!

[STPilot]

Putting a J&M CB on and am not quite sure which wire (color/colors) going to tail light do I want to use for power? I will use the frame as ground as suggested. Thanks in advance!

I installed my J&M about a month ago. I pulled power from the tail light assy. Black wire-with brown stipe is acc power to the tail lights. :D

[Fireball18]

BikerJoe,
Good morning. By which color wire to use for the power lead, I am assuming you know that the red wire that comes with the CB radio is the power lead for the radio itself. To get to the taillight/brakelight wiring, you need to remove the black plastic rear fender. If you lie down on the floor underneath the rear of the bike, you will see the wires. On my '03, the wire furnishing power to the taillights was a multi colored brown and green wire. I don't recall which one was the brake light wire. On my wife's '04, the wire was a different color, going to the taillights. So it depends on which year your bike is. If you have the shop manual, it should tell you which one is which, otherwise, a quick call to you STealer ought to get the right (hopefully) info. It's a bit tight getting in there to attach the wires, but should only take a few minutes once you have determined which is the correct wire.

A bit of important advice here--make sure you have a SOLID ground connection. I used a chromed bolt on the frame (see my post above) and have had no problems. While I see no technical problems with attaching to your battery for power, it poses a practical problem, in that you must remember to turn off your radio every time you shut the bike off, then turn it back on again when you restart, otherwise, your battery will eventually run down. The instructions from J&M specifically state not to tie into the battery for either power or ground. Good luck.

[STPilot]

Greg has a good point, I didn't realize different year models have different colors, my install is on my 04, so I guess your 05 could be different. Find a shop manual, that way you know for sure. :)

[Biddyman]

Out of curiousity, where did you guys mount the antenna? I'm asking for purposes of installing not the original problem.

[STPilot]

Out of curiousity, where did you guys mount the antenna? I'm asking for purposes of installing not the original problem.
I used a custom (read home made) bracket for the luggage rack. works great.:D

[joeseedoo]

I just went thru the same thing on a st1300.
What kind of head set are you using???? Is it a J&M It will make a difference.