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Radio
Broadcast Technical Consulting and Sales |
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AM Transmitter Filter Made in Minnesota |
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Here is a filter in the final stages of
being tuned and tested. This filter goes between an AM broadcast transmitter and an AM
antenna coupling network. The filter notches out a nearby AM radio station so that RF from
that station does not mix in the transmitter at the station with the filter. A mix product
could easily appear on another spot on the AM broadcast dial and cause interference to
another station. This filter is currently in use at WLFN Radio in La Crosse, WI. WLFN operates on 1490 KHz. Nearby WIZM-AM, on 1410 KHz, was getting into the WLFN transmitter. Without the filter there was interference to WKBH Radio on 1570 KHz. With the filter, the mixing product is down the required 73 DB below the WLFN carrier. The filter reduced the mix by about 20 DB. Shown, sitting on the filter, are an IFR A-7550 Spectrum Analyzer and a Delta RG-4 Receiver/Generator. On the floor are a Delta OIB-3 Operating Impedance Bridge, and a Potomac Instruments FIM-41 Field Intensity Meter. The FIM-41 makes an excellent RF voltmeter when it's loop antenna is switched off and an RF sample is brought in through a BNC input connector. |
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Questions?
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page last edited 05/11/2008
