Low Band shuts off Jeep Help

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flipped73

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Hi,
I'm not a ham operator. But I was hoping that someone here could help. I am a firefighter and investigator with our county J-Fire program. I am trying to use a Midland Syntec-1 on 46.44 for communications with our control center. However when I key the mic it kills the ignition in my Jeep Wrangler. In and effort to fix this I have installed a new antenna and rewired the power eliminating all the crimped connections in favor of soldered joints. I was told by the guy that did the programming that it benched at 110 watts. He also installed a pl board. Any suggestions would be appreciated.
Thanks in advance
Chris
 

N5TWB

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Ask your programmer to dial back your RF power. It will help the RF deck last longer and lower the amount of RF that can find its way into the vehicle electronics. You also did a good thing on going with soldered joints over crimped connections. Your next step is to confirm good grounding to the vehicle frame for the radio deck, control head, and antenna.
 

LtDoc

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... and after that, you get to find out exactly what's being interfered with and do the normal 'curing' of that! Not the simplest thing to do, but certainly do-able. By-passing, shielding, and grounding are the common 'cures'. I know nothing about a Jeep's electrical system and computer so won't even make a guess about how to go about all that finding and 'curing'. Yours isn't the only Jeep in the world being used like yours is, so there has to be a solution.
Good luck.
- 'Doc
 

zz0468

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In addition to all of the above, make sure that the antenna VSWR is low, and the antenna cable is routed away from existing vehicle wiring. There shouldn't be any excess coiled up, either. An antenna problem could cause the feedline to radiate into the vehicle and couple to the vehicle wiring.

You didn't mention what type of antenna it is, or where it's mounted, but that could be a factor. A roof mount loaded whip, or a ball mount on a rear fender should be pretty trouble free, if it's done right.

Reducing power could help, but there's no good reason in the world that you shouldn't be able to get a 110 watt radio to behave itself in a vehicle. I run 100+ watts on all bands from 3.5 MHz to 450 MHz, and have no interference to or from the vehicle at all. The key is proper installation.
 

rescue161

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I'd look into your alternator. It may not be putting out the proper amount of Amps. It may be just enough to keep the jeep running, but not enough for extra equipment, especially 110 Watts of extra equipment.
 

902

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How is the antenna and power wiring routed with respect to the Jeep's PCM computer? This sounds like you have stray RF being coupled back into the device through wiring more than a current draw issue, especially if you've wired directly to the battery. I'd also like to know more about your antenna. What kind is it? Base loaded? Ball and spring (the best for low band, as far as I'm concerned)? Hole or magnetic mount? Wire routing? Give us details! There are also some "great idea" installations, like placing a "L" shaped piece of metal with a 3/4" hole in one side for the antenna mount and a couple of self-tapping screws that go into the side of the cowling by the engine compartment. Those might not necessarily be such great ideas for a groundplane, or may be installed so that radiated energy is getting into the PCM (especially if you have that on the passenger's side... the alternative isn't any better because the thing that would soak the energy up would be YOU). You don't have many choices on a Wrangler. The other thing is how is the power cable routed? Considering the relatively small groundplane if you've got anything but a metal top, your cable may be acting as a counterpoise and carrying RF. If that's close to the PCM it might halt operation. Remember, that thing controls pretty much all your ignition, etc.

There's no reason you can't have a 110 Watt low band radio in your Jeep. The ultimate solution may involve changing some aspects of your install, like moving the power leads or snapping several ferrite cores around them, shielding in the affected device, and use ferrite beads and sometimes bypass capacitors to block RF. Antenna location, efficiency, and VSWR also play a role in this. Tell us more!
 

krokus

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Wirelessly posted (BlackBerry8530/5.0.0.973 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/105)

I would suggest having both of the radio's power leads wired directly to the battery. They both need to be fused, and you could install a power relay in the positive lead, controlled by ignition/accessory power, if you still have the radio switched by the keys.

What type of Jeep is this? There are major differences between the body styles and years.
 

zz0468

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As was stated earlier too much draw on electrical system. Need to lower the wattage a tad.
Really!? I suppose that would depend on where the power is coming from. A direct connection to the battery would have minimal impact if it's a reasonably healthy electrical system. A tap off the fuse block would likely blow a fuse somewhere before it killed the engine.

To the OP - This can easily be tested by putting the radio on a dummy load and seeing if the problem persists.
 

Confuzzled

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And if nothing else works, have you checked with a Jeep dealer? They may be able to point you to something that would be affected by radio.
 

smokeybehr

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Checklist:

Power leads run directly to the battery with fuses only in the positive lead.
Good quality coax used to connect to the mount.
Antenna mount properly installed as far from the ECU as possible.
Antenna cut for the proper frequency. (This is a big one)
Grounding straps run between the engine, body and frame.

If all of the above are done, then I'd dial back the power to about 75W. You don't want to dial it back too far, or some strange things might happen.
 

OCO

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And if nothing else works, have you checked with a Jeep dealer? They may be able to point you to something that would be affected by radio.
Tell 'em to dig out their TSB's from the mid-late 70's, cross ref with "CB", "linear, lineeeeer, footwarmer" or "computer now toast"..
 

rescue161

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If the alternator is going bad, then it won't matter where power is coming from. Do as zz0468 suggests and put a dummy load on the output. If the engine still dies, then it's time for another alternator. They sell heavy duty alternators for pretty cheap.

Does your Jeep have air conditioning? Usually vehicles with AC will already have a larger alt. If yours does not have AC, then I'll bet that you have a standard alt. and it can't keep up with the demand that the 110 Watt radio is requiring.
 

ipfd320

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theres an easier way to see if the alternator is no goo--while the car is running pull off the positive sied battery lead--if the car shuts down then theres the problem (alt. output)--you can also check output voltage with a meter across the battery teminals 13.8-14.3 volts is the ideal range--then check the output with everything oh (heaters full blast-all lights-rear defroster-and whatever else you got) then check output again--if it drops below 12.3 its a done deal---suggestion is if its that is to have the alternator modified to higher output amperage---thats what i had to do to by old 79 blazer when i installed alot of lighting and radio accessories....good luck
 

rescue161

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theres an easier way to see if the alternator is no goo--while the car is running pull off the positive sied battery lead--if the car shuts down then theres the problem (alt. output)--you can also check output voltage with a meter across the battery teminals 13.8-14.3 volts is the ideal range--then check the output with everything oh (heaters full blast-all lights-rear defroster-and whatever else you got) then check output again--if it drops below 12.3 its a done deal---suggestion is if its that is to have the alternator modified to higher output amperage---thats what i had to do to by old 79 blazer when i installed alot of lighting and radio accessories....good luck
This, for the most part, is true. My trucks alternator was bad, but I didn't know it. I pulled the positive lead off while the truck was running and everything looked okay (truck didn't turn off). I reconnected the battery cable and had 13.8 volts read across battery when the truck was on and everything was running (AC, lights, radio, etc.), but it was not producing enough current to actually charge the battery when everything was running/on. As long as idle was high (driving), then everything was fine, but during an idle, it would fall below the norm. I went through several batteries before I finally took the alternator off and had it tested. It was bad. It put out the correct Voltage, but not the Amperage that it was suppose to.

A Voltage reading won't always tell you the problem, as mine was putting out 13.8 Volts.
 

OCO

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IF it was a bad alternator and a bad battery, turning on the headlights (110 watts on high beam) and the heater blower would kill it too (and it probably wouldn't start in the first place if the battery was that low). Even if the alternator is bad, the battery should handle the 110 watt transmitter for at least a 1/2 hour of continuous keydown - assume about a 45 amp/hour rating for an average 700 CCA battery. Unless the radio was wired directly to the line feeding the computer, this is highly unlikely to be a voltage drop issue - it's RF getting into the computer.
 

rescue161

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IF it was a bad alternator and a bad battery, turning on the headlights (110 watts on high beam) and the heater blower would kill it too (and it probably wouldn't start in the first place if the battery was that low). Even if the alternator is bad, the battery should handle the 110 watt transmitter for at least a 1/2 hour of continuous keydown - assume about a 45 amp/hour rating for an average 700 CCA battery. Unless the radio was wired directly to the line feeding the computer, this is highly unlikely to be a voltage drop issue - it's RF getting into the computer.
Not if that alternator is bad. If that alternator is bad (barely working to charge the battery), then it will not charge the battery to full capacity, so relying on a battery that isn't fully charged to compensate for a bad alternator is not going to happen.

We won't know if it's RF getting into the computer until he (OP) does as ipfd320 as well as I have suggested and do those simple tests. There is no sense in chasing an RF leak if there isn't enough power to run the system in the first place.

Troubleshoot in simple steps!

1) Turn on everything in the vehicle (heater, lights, etc.) and then disconnect the battery. If vehicle remains running, then the alternator is likely good. If the vehicle turns off, then the alternator needs to be replaced.
2) Put a dummy load on the antenna output of the radio and key it up. If the vehicle turns off, then it more than likely the alternator. If the vehicle remains on, then you have an RF leak problem.

Another note would be to not run the negative lead to the battery, but to make it as short as possible and terminate it to the frame. Be sure to check the resistance between your ground and the batteries negative terminal. If you have any resistance, then you need to change your ground location or you need to use grounding straps as someone else suggested to bring that resistance to zero.
 
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OCO

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So the battery can handle the 200- 300 amp or so draw from the starter cranking, but not the 30 amp load from the radio... :roll: Have at it, I'll keep my opinions out of this one....:D
 
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rescue161

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So the battery can handle the 200- 300 amp or so draw from the starter cranking, but not the 30 amp load from the radio... :roll: Have at it, I'll keep my opinions out of this one....:D
Yeah, it can happen. Especially if that 30 EXTRA Amps is just that, EXTRA.

Everyone is basing all of their suggestions on the vehicle having a healthy electrical system.

We won't know until the OP reports back his findings.
 
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