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| Reviews Summary for Radio Shack FM Trap 75 ohm |
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Reviews: 1
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Average rating: 5.0/5
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MSRP: $8
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Description: Great device for removing the strong FM broadcast stations from intermoding Scanners or other recievers. The filter contains three notches that are spread out to remove most of the fm broadcast band. attn is from 30 to 40 db.
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More info: http://www.radioshack.com
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write your own review of the Radio Shack FM Trap 75 ohm.
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KF6CM
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Rating: 5/5
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Jul 10, 2007 16:59
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Needs to be adjusted.
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Time owned: 3 to 6 months
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I have purchased over ten of these filters and found that every one of them only attenuating 88 MHz by 6 db. They were all very consistant. By simply adding one turn to the low frequency notch I was able to knock 88 MHz down by 40 db. With two filters in series I was able to get 80 db of attenuation. Now my scanner will scan.
Scrape off the glue that holds the back plate. Then carefully pry off the back plate. locate the small coil that is on the INPUT terminal. It should have 5 turns. clip out only the coil leaving the parallel capacitor attached. Using 24 gage wire make a new coil with 6 turns. use a .125 dia shaft of a drill bit for a form. attach the new coil across the capacitor. I cheated and used a R&H Spectrum analyzer with a tracking generator to verify that it works. Now the entire FM band is gone! (The middle coil and the coil on the OUTPUT terminal needed no adjustment.) I use an outside diskcone antenna at 50 feet on my scanner.
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