Birdies?
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_1_2 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7D11 Safari/528.16)
Hello everyone
I am in the southern part of Puerto Rico and my scanner is stoping constantly on the following frequencies. They are very strong all over the south.
The frequencies are:
410.8125
415.4750
417.6125
419.8125
408.6125
the carry a constant transmission, no voice or control channel data. Could it be telemetry?
There is a Tethered Aerostat Radar nearby, could this be the culprit?
Any info or insight will be gladly appreciated.
A birdie is a false, or phantom, signal that appears in a superheterodyne wireless receiver. Birdies are internally generated, resulting from the outputs of the oscillators that form part of the receiver circuit. They usually sound like unmodulated carriers -- signals with "dead air." Occasionally they are modulated by clicks, humming sounds, or audible tones.
Birdies can occur as a result of the receiver being tuned to a frequency that is a multiple of the output frequency of one of the internal oscillators. These signals are known as harmonics. A birdie might also be heard at a frequency corresponding to the sum or the difference of the internal oscillator frequencies. These signals are called mixing products. Birdies are inevitable in any superheterodyne wireless receiver. However, in a well-engineered receiver, most or all of the birdies occur at frequencies outside the normal range of operation, so they have little or no detrimental effect on receiver performance.
A birdie is not the same thing as a spurious response. If a receiver picks up a signal whose transmitter is operating at a frequency other than that to which the receiver is tuned, the modulation of the unwanted signal will be heard or decoded. In some cases, two or more strong external signals can combine in a receiver's radio-frequency amplifier, causing numerous spurious responses. This phenomenon, called intermodulation ("intermod"), can be a problem in downtown metropolitan areas where many wireless transmitters operate simultaneously.
