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Message |
    
Tech833
Moderator
Username: Tech833
Post Number: 2209
Registered: 8-2002
| | Posted on Wednesday, September 26, 2012 - 2:07 pm: | 
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Working on a super secret project.
Need to know, what affordable models of CB rados (legal ones only, no "export" radios, please) will work in a vehicle with a positive ground electrical system.
So far, have only found the Uniden Pro 505 XL and 510 XL that are compatible with positive or negative ground systems. There must be more. Anyone know of some current makes?
Thank you in advance.
Your radio 'Mythbuster' since 1998
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Milkman21218
Advanced Member
Username: Milkman21218
Post Number: 506
Registered: 1-2004
| | Posted on Wednesday, September 26, 2012 - 7:32 pm: |
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Years ago when I drove Big Rigs for a living. We had so Whites that had Pos ground. We just switched the Neg & Pos hookup. And my Cobra, Sears, Rat Shack and GE CB radios all worked just great.
Izzy
CEF#502
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Tech833
Moderator
Username: Tech833
Post Number: 2210
Registered: 8-2002
| | Posted on Thursday, September 27, 2012 - 1:07 am: |
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Yes, I am aware that some of the older rigs were compatible with positive OR negative ground systems.
My request was for current make radios available right now. Preferably, the "bargain" radios, those under $50.
I cannot tell you what this is for, but it will become apparent soon enough, if everything works out.
Your radio 'Mythbuster' since 1998
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Tech237
Moderator
Username: Tech237
Post Number: 1619
Registered: 4-2004
| | Posted on Friday, September 28, 2012 - 8:57 am: |
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Currently NONE, unless you take some extreme precautions. Such as - mouting the radio in a plastic box to isolate it from ground. Use a capacitor (arounf 100pF) in the coax ground lead.
Even then this is not 100% perfect - ask me how I know.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Milkman21218
Advanced Member
Username: Milkman21218
Post Number: 507
Registered: 1-2004
| | Posted on Friday, September 28, 2012 - 4:47 pm: |
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I still say just switch put the positive from the radio to the Negative on the battery. And negative from the radio to the positive on the battery should still work the same as it use too.
Izzy
CEF#502
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Tech237
Moderator
Username: Tech237
Post Number: 1621
Registered: 4-2004
| | Posted on Saturday, September 29, 2012 - 8:43 am: |
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Milkman - only if the radio is mounted above ground. The case on most radios is grounded to teh negative lead.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Unit199
Advanced Member
Username: Unit199
Post Number: 761
Registered: 8-2003
| | Posted on Sunday, September 30, 2012 - 8:42 pm: |
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If you reverse the polorization on these newer radioes you will either blow the fuse or the radio. Not a good idea at all.
HARVE
UNIT199
CEF0210/CVC#018/HAM#010
Midwest 10 Meter Net Controller
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Tech833
Moderator
Username: Tech833
Post Number: 2212
Registered: 8-2002
| | Posted on Thursday, October 04, 2012 - 3:37 pm: |
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Obviously, you never want to reverse the power cord polarity on ANY mobile radio.
The trick to finding a radio that will work with a positive ground vehicle electrical system has to do with the radio itself either having floating ground or ground independent.
If you hook up a negative ground only radio in a vehicle with a positive ground, assuming you ran the power cord directly to the battery, you are just fine until you connect the antenna. When the coax shield comes in contact with the chassis of the radio, you have a direct short, and usually no fuse on the negative side of the power cord, resulting in melted radio.
I suppose you could easily isolate the coax shield from the radio chassis ground with capacitive coupling. However, this isn't the intent of this project. Eventually, if Copper's papa likes what he sees, this project may eventually see the light of day, and I'll be the first to introduce you to it. If not, then we'll sweep it under the rug along with all my other bad ideas.
73,
Your radio 'Mythbuster' since 1998
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Chris142
Intermediate Member
Username: Chris142
Post Number: 128
Registered: 7-2002
| | Posted on Thursday, October 04, 2012 - 10:13 pm: |
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So use a magnet mount antenna and insulate the case and bracket from the body of the car.
I'd use a junk radio to make sure things are correct before plugging in my good one. |
Tech833
Moderator
Username: Tech833
Post Number: 2213
Registered: 8-2002
| | Posted on Friday, October 05, 2012 - 11:26 am: |
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Yes, that's one way to do it.
This particular project calls for a radio that is permanently mounted and an antenna mounted so that high-dollar paint is not damaged. So, the magnet is out. That was my first choice also. I spec.'ed a mag mount with an extra rubber or felt pad stuck to the bottom. No-go.
Your radio 'Mythbuster' since 1998
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Milkman21218
Advanced Member
Username: Milkman21218
Post Number: 508
Registered: 1-2004
| | Posted on Friday, October 05, 2012 - 12:23 pm: |
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I have not seen a Positive ground vehicle in the last 20 years. But I do know that the Semi's that I drove that had Pos ground we would hook the radios up backwards for them to work. The first time I hooked the radio up I went Pos to pos and neg to neg it blew the radio. Then I was told that rig had pos ground and to hook up radio pos to neg. And it worked for the next 2 years with any of my CB radios. And the mirrow mount antennas. So that must mean radios are not made the same today. I ran GE, RS, Cobra 29 LTD, and GTL148. All worked and still do! So I would like to know what was changed in the radios?
Izzy
CEF#502
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Tech833
Moderator
Username: Tech833
Post Number: 2216
Registered: 8-2002
| | Posted on Saturday, October 06, 2012 - 12:00 am: |
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The clue you just gave us is that you had mirror mount antennas, therefore grounded to the truck. When you connected your radio, it must have been a negative ground only unit, you essentially shorted the positive (ground) to the negative battery terminal (battery hot).
That is EXACTLY why I am asking this question here, searching for other current make radios that will work on positive ground systems.
Connecting any radio "backwards" regardless of the vehicle ground system, is a very bad idea. Connecting a radio with reverse polarity WILL damage something. You cannot connect a radio "backwards" and have it just work like normal, unless there's a bridge rectifier in there somewhere we don't know about. But that still doesn't make it positive or negative ground compatible.
For the sake of this ensuing discussion, let's not confuse "polarity" with "ground".
Your radio 'Mythbuster' since 1998
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