Unknown (V.29 fax machine) modem

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Possible backhaul from an ITU V series type modem for trunked voice control from a leased line
Unknown fax machine modem 454.425 MHz.PNG
Frequencies 406 MHzMegaHertz (MHz) 10^6 Hz406,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
406,000 kHzKiloHertz (kHz) 10^3 Hz
,455 MHzMegaHertz (MHz) 10^6 Hz455,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
455,000 kHzKiloHertz (kHz) 10^3 Hz
Frequency Range 406000000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).406,000 kHzKiloHertz (kHz) 10^3 Hz
406 MHzMegaHertz (MHz) 10^6 Hz
455000000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).455,000 kHzKiloHertz (kHz) 10^3 Hz
455 MHzMegaHertz (MHz) 10^6 Hz
Mode FMFrequency Modulation
Modulation QAMQuadrature Amplitude Modulation
Bandwidth 8 KHzKiloHertz (kHz) 10^3 Hz8,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
0.008 MHzMegaHertz (MHz) 10^6 Hz
kHzKiloHertz (kHz) 10^3 Hz
0.008 MHzMegaHertz (MHz) 10^6 Hz
kHzKiloHertz (kHz) 10^3 Hz
0.008 MHzMegaHertz (MHz) 10^6 Hz
Location unknown
Short Description Here is a signal that had popped onto my SDR earlier this summer, and it sounds like a typical fax machine modem using regular 9,600 baudBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second.. Reasons I will describe below, and with audio samples coming in the future, I have never seen such oddity around here. Even stranger this signal is on 24/7 365 days a year. Only difference, it transmits a morse identifier I have yet to capture, but due to it being so far away, I cant capture it anymore. Also, apologies if the quality of the audio file is bad, as antenna was not good enough.
I/Q Raw Recording
Audio Sample

There are also some that are currently active in a fellow user's State (CA), in which his signals have appeared in part of the government band, 400-420 Mhz. Audio will also follow.

Samples[edit]

Here is a typical V29 standard QAMQuadrature Amplitude Modulation fax modem that was posted by a person named Lui Gough: https://goughlui.com/wp-content/uploads/2013/02/V29-9600bps-ECM.wav


And here is an audio clip of a stranger one, some of which have actual preambles inside it. Images will follow later.



Waterfall Images[edit]


Alright. MORE news/updates.

The fellows on our discord server have actually found a **possible**, this doesnt mean 100% true fact, ties to ITU v series modems, including this v.29, that is not being used for fax. It is instead being used for trunking voice channels, that are being used over *leased lines*, which then front-end to RFRadio Frequency transmitters spanning the UHFUltra High Frequency (300-3000 MHz) band by backhauling.

Once again, this is only a possibility.


To prove this, or at most provide an example, here is a PDF of how it would work aside from Canada's Moose Jaw Police Service that operates such an oddity infrastructure in a similar fashion.

https://moosejaw.ca/wp-content/uploads/tenders/RFP%20MJPS%20Radiocommunication%20Infrastructure%20Technical.pdf

There is also a RadioReference forum topic that has talks about v.32 with ASTRO voice transfer using 14,400 baudBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second. with ASTRO's 9600/4800 baudBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second. voice controls, as both sum up to the modem's baudBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second. speed.

Also, this modem usage could act as a medium for better quality with quite possibly narrower bandwith too, as leased lines are always active and have a fixed monthly fee. Hence the reason why these modems are constant carriers that sound like their "faxing nonsense" over the airwaves. But in reality, its trunking data and voice being transmitted on an FMFrequency Modulation carrier with narrower bandwith and quality.