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After many years without it, the original Wonderbar is back in my '62. I'm trying to remember how good and bad the reception on these radios was. It's been 30-40 years since I listened to AM radio. The antenna is new and extended all the way. All the shielding and capacitors are in place. The generator capacitor looks bad though. The reception in the city is great - lots of stations, static in between stations. However, 40 miles out of the city, all I get is static and the stations come in faintly. The intensity of the static increases with engine rpm. Is this normal? I'm wondering about my shielding. Shouldn't the shielding take care of all the static? I understand the faintness of the station at a distance. But I'm surprised about the amount of static. Has there been any filters invented since 1962 that'll cut down on the static?
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Re: C1 Radio Reception
Chris...
Sounds like a 43 year old radio...All you have is the Front wheel static collectors, ignition shielding and capacitors. Good thing the antenna is on the rear, far from the engine!!! -
Re: C1 Radio Reception
There are two ways for interference to couple with radio reception: conducted and radiated. The strategically placed radio RF capacitors were basically designed to thwart conducted radiation (nip it at its source and prevent it from traveling down the car's electrical system to the radio). The sheilding was designed to reduce (not eliminate) interference radiated from the ignition system.
AM reception is quite sensitive to interference because the audio information is derived from the amplitude of the received signal vs. FM where the information is derived from the frequency of the received signal. Something is DEAD wrong if you're getting objectionable interference only 40 miles away from a major metro transmitting antenna. At 75 miles or more, maybe yes...
AM radios are VERY sensitive to the integrity of the antenna while FM receivers are pretty tolerant of antenna integrity. Quite frequently I see the problem to lie in the radio antenna's lead-in wire. It's a human-hair, thin, wire traveling inside a shielded cable that's pretty easy to fatigue fracture. This susceptibilty is easy to compound if the lead-in is 'abused' by handling.
In order to restore an interior, old carpet has to be torn out and fresh carpet laid/glued in place. Plus, just pulling the banana plug out of the radio chassis without reasonable care and due diligence can 'kink/break' the lead wire where it's soldered to the plug tip...
If the antenna lead-in wire is factured, recieved signal strength drops like a rock and the radio's front end amplifier goes to its rails trying to recover sufficient signal to demodulate. Unfortunately, when you amplify a signal laden with noise, you blow up BOTH the signal and the noise! The quality of reception comes from the signal to noise RATIO (how much larger is the signal compared to surrounding noise interference).
A cheap and easy test is simple. Listen to the radio with the engine not running and compare that to what you hear with the engine running. If there's a whinning noise that runs in lock-step to engine RPM, start looking at the generator as your source. Now, take another step.
Trot on down to WalMart and buy yourself an el-cheapo replacement radio antenna pre-packaged with captive lead-in cable. Expect to spend $8-10, cheap, eh?
Now, carefully disconnect the lead-in wire from your car's built-in antenna at the rear of the radio and substitute the known good, new, antenna from WalMart and re-run the test. When you come to the point of firing the engine, have an assistant walk the antenna mast out of the cockpit toward the rear of the car (mimic the factory distance between antenna mast and engine compartment).
If you see a SIGNIFICANT difference in the quality of radio reception, you can pretty much bet your existing lead-in cable is damaged and it's time to replace it! T******* the radio to the cable (a variable capacitor you turn with a miniature screw driver) can also help to get the receiver-antenna impedance coupling characteristics dead nuts on.
BUT, the advantage of being 'tweaked' will only show up with any real degree of notice when you're driving in the 'boondocks' under bona fide fringe reception conditions. Still, if you do have to replace the antenna lead-in cable OR if the radio's recently been out for service (it was on somebody's tech bench and tweaked for THEIR antenna), it's a good thing to re-adjust the chassis for your car/antenna....Comment
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What sorta plus and wires
do you have? I have ordinary 7mm wires, and 43R plugs, all the factory shielding and capacitors, and no increase in static with rpm. Resistor plugs are OE on my car.Comment
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