VHF Radar in DC area

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dlwtrunked

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Transmissions from the tethered aerostat radar at Aberdeen, MD occur centered on 138.3125 and 149.4375 MHz. The system sends intervals of pulses that alternate between these two frequencies. At altitudes like 10,000 feet, the transmissions are easily heard at distances overt 100 miles. Due to the high pulse repetition rate, these have a bandwidth over 100 kHz (about 100 kHz @ -10 dB, 150 kHz @ -20 dB, and easily seen over a 400 kHz bandwidth). They can be heard in AM, FM, or WFM modes, but are best heard in AM mode. As the pulses are very short, when received this way, the audio will contain harmonics of the pulse repetition rates. This system's signal has been also heard generating weak signals in the 2-m band as well as in 150 MHz range clear into central Virginia.
 
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