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Radio
Broadcast Technical Consulting and Sales
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1-5/8" FM Harmonic Filter |
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Construction and tuning by Mark Persons Made in Minnesota |
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This is a view of Mark in the shop. The copper tube shown here is a second harmonic
trap for an FM broadcast transmitter. This trap was custom built and tuned in the
shop at a lower cost than one that is commercially manufactured. It is currently
being used on the KKCQ-FM Gates FM-10 Transmitter at Bagley, Minnesota. Attenuation
at the second harmonic exceeds 30 DB.
The instrument, on the bench, is an IFR A-7550 Spectrum Analyzer with tracking generator. The IFR works from 100 KHz to 1 GHz and is excellent for looking at RF emissions and RF circuits. Analysis is done in minutes rather than hours by previous methods. |
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The left plot is a return loss measurement of the filter. The operating frequency of the radio station is in the middle where the match is the best. The right hand plot shows return loss at both the station's frequency and at the second harmonic. The match is good at both frequencies. The exception is that the filter absorbs the second harmonic while passing the station's main signal. |
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Questions?
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page last edited 05/11/2008
