I recently installed a radio in a 1968 beetle and it is having some problems with fm reception. I have been trying to find some information about improving the fm reception without much luck. Perhaps it is not possible but I wanted to check with the knowledgable people on this forum.
Aside from the "FM Sensitivity" of the deck, is there anything else that can be done to improve the fm signal? Have there been any recent (last 10-20 years) improvements in the design of automotive antenna's that would warrant the purchase of a newer one?
Thanks in advance, I appreciate any and all information.
Most of the newer vehicles now a days have coiled antenna's. My vehicle doesnt have one, but you can tell one when looking at it. The antenna rod is coiled with the reception lead which is wrapped from the top going down to the vehicle. I have heard from tons of people that a coiled antenna gets much better reception than a non coiled.
An antenna mast that is coiled is no better than most other antennae. There are a number of things you can check to insure that your antenna is wworking at 100%. The majority of antennae are optimized for the radio that comes with the car nowadays. In years past, the antenna mast was generally standardized at 31 inches long. The antenna mast only receives half of the FM signal though. The other half is received through the ground plain of the antenna. The ground plain is the body of the vehicle. Use a meter set on impedance (ohms scale) to measure the continuity of the antenna. From the center lead tip at the radio to the antenna mast you should have less than 0.5 ohms resistance to ground for leads up to 5 feet. If the lead is over 5 feet, the reading can be higher, but should not exceed 3.5 ohms at the 20 foot mark. The outer shield contact at the antenna lead tip should have less than 0.5 ohms resistance to ground, no matter how long the lead is. The reading between the center tip and the outer shield should be infinite. The radio should also have a good ground.
Antennae come in many forms. The reason that you know see many coiled antenna masts is for two reasons. One it reduces wind noise and two it allows for shorter antenna masts. If you uncoil the antenna wire, it will measure 31 inches.
Don't confuse poor reception with noise though. Try the radio station with and without the engine running. If you have noise then you need to rethink things and find what is causing the noise. Finally, all radio tuners aren't created equally. Some are better designed than others.
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sparky
I appreciate the info sparky! I should have a chance to check the resistance of the antenna and the grounds tommorow. I found an "Electronic FM Booster" on ebay that claims 12db gain on FM and 10db on AM. Do you think that the booster would help if the antenna is good, and possibly even if it is not?
Thanks again!
FM boosters are junk. All they do is boost what you already have. So if you have a noisy signal, you will have a very noisy signal after adding the booster. The only time they may help is on boats that aren't near any radio stations. Save your money. A antenna that is in good shape and correctly installed and a good radio tuner is all you need. If all else fails, turn on the CD player.
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sparky