Any ideas on why my FM is great but AM only works when I "unground" the power antenna. I have substituted a different radio and have the same problem. Thanks in advance for your help.
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Re: AM Radio
just a guess - there is an AM antenna tuning capacitor intergral with the am section ONLY. I think it is behind the tuning knob - did you mention the year.? in any event this must be adjusted as follows - tune to a LOW end of the dial - about 540 KHz. adjust the capacitor slot ( small flat head screwdriver ). The screw driver MUST be ceramic or plastic handled so as not to affect the capacitor) - your hands can have as much as 50 pico farads and this can completely de tune the set - TUNE FOR A WEAK STATION for the most volume. Now go to the high end of the dial about 1 MHz of more - retune on a weak station for best volume. Now go back to the low side and check again - life is a compromise .... The adjusment screwdrives are available at radio shack - good luck. ALSO -- MAKE SURE that the ground connection is good at the antenna _ unfortunately on some vetts this is located close to the gas tank and may be hard to see clearly let alone checking for corrosion which can also cause your problem. Just lossen the darn thing, spray with liquid wrench and retighten if in doubt. -
Re: AM Radio
Adjusting the impedance trim pot will only get you a significant performance difference in fringe reception areas (low signal strength). In a major metro area, the trim cap will make virtually no difference (that's why trim proceedure suggests finding a weak station to work with).
Symptoms poster reports are CLASSIC indication of faulty (open circuit) antenna and/or antenna lead-in cable. A number of threads on this are in the archieves.
Bottom line: go to K-Mark/WalMart, get a generic replacement radio antenna ($5-8), unplug the existing bannana plug antenna jack from the existing radio, plug in the known good replacement antenna, move it out of the cockpit toward the rear of the car as far as you can get it (assistant helps), and re-fire the radio. If SUDDENLY you get AM reception (odds are real good), it's telling you some 'buba' before you damaged the existing lead-in cable and/or the connection of the lead-in cable at the rear mount antenna is defective.Comment
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