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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / March 2008radio antenna problem
My 1996 Jeep Cherokee Sport just developed a problem. Overnight the radio went from being pretty good to one that gets nothing but static. The tape player works fine. My first thought was the antenna came unplugged from the radio. I pulled off all the plastic crap and pulled the radio. The antenna was plugged in. I stuck a piece of insulated wire into the female antenna connection and got good FM but no AM reception. So, I assumed the radio is OK and there must be a problem with the coax going from radio to the antenna. I measured the resistance from the tip of the connector that goes to the radio to the outside antenna and got high resistance - several megohms. The resistance from the outside of the coax connector to ground is high as well. Is there any solution other than replacing the antenna coax? My guess is that the resistance for both should be only a few ohms. Right? Is it reasonable that the antenna coax would go bad like that overnight? Is the coax one piece from radio to antenna or could there be some connection that has come lose? How hard is it to replace the coax (without completely removing the entire dashboard)? Oh, there have been no accidents or traumatic jars to the car other than a few holes in the road. Right now I'm driving around with all the plastic in the back seat and my jerryrig antenna wire laying on the dash. That's OK with me but my bride doesn't like it. > My 1996 Jeep Cherokee Sport just developed a problem. Overnight the > radio went from being pretty good to one that gets nothing but static. [quoted text clipped - 17 lines] > in the back seat and my jerryrig antenna wire laying on the dash. > That's OK with me but my bride doesn't like it. Tearing the dash out versus getting a new bride? hmmmm... that's a tough one. >> My 1996 Jeep Cherokee Sport just developed a problem. Overnight the >> radio went from being pretty good to one that gets nothing but static. [quoted text clipped - 21 lines] > >hmmmm... that's a tough one. Here is a big issue: antenna lines are NOT made of coax. They are not actually operating as transmission lines at all, but are designed like scope probe cables with a super high-impedance source and load. (This is because the antenna is a stub much shorter than a quarter-wave, driving a high impedance input on the radio.) The cable is shielded, but it has a VERY thin center conductor in a loose internal tube. That center conductor can be easily broken at the connector on either end, and it can break in the center too. A "Fox and Hound" telecom cable tracer can help you find the break. Otherwise you will have to pull a whole new pre-terminated cable assembly from the dealer in there. --scott  Signature"C'est un Nagra. C'est suisse, et tres, tres precis." Thanks folks. I learned a lot. Since the only test equipment I have is a VOM it sounds like the only solution is to buy an new one and try to put it in. I'm guessing from Scott's post that the existing one is broken somewhere. Now I'm starting to wonder if there is any harm to the radio in just leaving the "wire" antenna in. That may be the easiest and most cost effective. This is my car not the wifes and I could care less if there is a wire hanging out on the dash. > In article <TEwFj.21218$Ch6.12...@newssvr11.news.prodigy.net>, > [quoted text clipped - 42 lines] > > - Show quoted text - There is something about Jeep Cherokees and radios... Very few older ones work well at all. Both ones we owned quit bringing in FM. AM and the tape still worked. I personally would be tempted to use your fix. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos: http://mikeromainjeeptrips.shutterfly.com > Thanks folks. I learned a lot. Since the only test equipment I have > is a VOM it sounds like the only solution is to buy an new one and try [quoted text clipped - 47 lines] >> >> - Show quoted text - >Thanks folks. I learned a lot. Since the only test equipment I have >is a VOM it sounds like the only solution is to buy an new one and try [quoted text clipped - 3 lines] >easiest and most cost effective. This is my car not the wifes and I >could care less if there is a wire hanging out on the dash. It's not hurting anything, but it would drive me up the wall, personally. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." > My 1996 Jeep Cherokee Sport just developed a problem. Overnight the > radio went from being pretty good to one that gets nothing but static. [quoted text clipped - 8 lines] > resistance from the outside of the coax connector to ground is high as > well. Is there any solution other than replacing the antenna coax? Depending of which antenna type is installed. Some wipe antennas could be equipped with an amplifier, in this case a high resistance between the tip and the wipe could be possible. If not it should be zero ohm, and in case with an amplifier it should be fed. Resistance between shield and chase should be zero in booth cases. Regards, Ralf
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