Carrier only signals ?

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focaton

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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.
 

signal500

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Birdies?

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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.
 

focaton

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I doubt them to be birdies. They are not unmodulated. You can clearly discern a data signal of some kind. The winradio signal classifier shows It to be data. Also verified each frequency with a DJX10t and a BCD396XT. I doubt that the three radios have birdies in the same frequencies.
 

signal500

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I doubt them to be birdies. They are not unmodulated. You can clearly discern a data signal of some kind. The winradio signal classifier shows It to be data. Also verified each frequency with a DJX10t and a BCD396XT. I doubt that the three radios have birdies in the same frequencies.
Well, with the further information you provided, I would say they are not birdies. Maybe it is coming from the Tethered Aerostat Radar, though I doubt it at those frequencies. I do know of an encrypted radio system that has a data carrier only while transmitting without the usually "open squelch" sound from a typical DES/DES-XL system. Sorry that I couldn't be of more help.
 
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focaton

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Just to be absolutely sure I changed the IF freq on my bcd396xt and I still get the signals.

I don't hear any mic unkey, it's just a constant signal. It is kind of similar to the remote tv broadcast pickup signals on UHF
 

CqDx

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A while back we have the exact same situation you described, one frequency in 416MHz was constantly transmitting, but no PL/DPL or modulation. It is as simple as that, just a constant carrier.
 

focaton

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