Any ideas on what this signal is?

[BM82557]

 

[ka3aaa]

dont hear anything and cant tell by looking at the screen, could be anything.

 

[kruser]

Do you have a sample of the actual audio?

 

[BM82557]

Do you have a sample of the actual audio?

No, was recording other activity at the time I noticed this.


Is air/ground radiotelephone still in use?

 

[nd5y]

Is there anything on 454.875?
I think the 454/459 air-to-ground spectrum was auctioned off. There is no telling what is there now.

 

[nd5y]

It looks like almost all the 454/459 MHz air-ground licenses belong to:

AURA

AURA (which stands for Advanced Ultra Reliable Aviation) is on a mission to deliver an FAA-compliant nationwide network utilizing unique, licensed aviation spectrum to enable advanced levels of autonomy in the National Airspace System.

auranetworksystems.com

AURA is currently testing technology that the aviation industry assumed was several years away. We have the only coast-to-coast network transcending state boundaries with coverage in Alaska and Hawaii, as well as Puerto Rico and substantial portions of offshore waters. As the exclusive operator of our 454/459MHz aviation band spectrum, our site locations ensure a nationwide, interference-free service over a secure, private network.

Our signal serves the National Airspace System (NAS), providing pilots with predictable, reliable command and control (C2) and air traffic control (ATC) voice services.

 

[trentbob]

Actually, could be, .. anything. So hard to pinpoint and identify.

 

[AB4BF]

View attachment 146347

Here in SC, Dominion Energy's smart meters run on 459.500 MHz. Could be a smart meter. We have verified the frequency many times using a spectrum analyzer.

 

[ecps92]

Is there anything on 454.875?
I think the 454/459 air-to-ground spectrum was auctioned off. There is no telling what is there now.

Altho auctioned off in the US, I have heard some in Northern New England - but could have been from Canada.

Being the ole A/G was going to be my first comment to post when I first saw the OPs thread

 

[nd5y]

Here in SC, Dominion Energy's smart meters run on 459.500 MHz. Could be a smart meter.

The band edge between air to ground and paging is 454.6625/459.6625.
459.500 is paging which is an entirely different discussion.

 

[BM82557]

Active again today but the signal was weaker --

 

[Ubbe]

It's a huge 75KHz modulation bandwidth, that could indicate analog HiFi audio. I know there are some headphones working in that frequency range. It would help listening to an audio clip and if it's digital there might be someone who recognize it and can match to a certain device.

/Ubbe

 

[nd5y]

It's a huge 75KHz modulation bandwidth, that could indicate analog HiFi audio.

If it was analog audio the waterfall would not have broken horizontal gaps at regular intervals.
If there were pauses in the audio the carrier would appear as a vertical line in the middle.

 

[Ubbe]

You're right. It's bursts of full modulated carrier with different time lengths and then a short silent carrier with no modulation between burst. It seems to be a single sideband pilot tone at around 50KHz to the left. Or it could be some artifact from a sampling rate, 44Khz or 48KHz perhaps.

This is from a Airspy R2 mini that doesn't have any additional bandpass filters for its R820/R860 receiver chip, so are prone to overload. It could be a mix of two signals and could probably be checked if it is strong enough to allow to lower the gain 10dB and see if the signal also goes 10dB down. If it goes down more it is intermodulation of several signals.

/Ubbe

 

[IC-R20]

Looks like an RTK signal but you keep failing to record audio of it. Honestly even just FM demodulated audio off the handheld radio would go to help a lot.

 

[Ubbe]

The RTK signals I've heard have been narrow FM but this is 75KHz and a pilot tone like it would be if it where a FM broadcast signal. In Europe there's a 57KHz RDS signal for road traffic information but in US I believe its used for other purposes and the interruption in the modulation could be that the other signal it mixes with are a transmitter that pulsate its carrier. It's probably not allowed to use 75KHz wide channels on that frequency in US, so it has to be intermodulation from other frequencies.

/Ubbe

 

[dlwtrunked]

The RTK signals I've heard have been narrow FM but this is 75KHz and a pilot tone like it would be if it where a FM broadcast signal. In Europe there's a 57KHz RDS signal for road traffic information but in US I believe its used for other purposes and the interruption in the modulation could be that the other signal it mixes with are a transmitter that pulsate its carrier. It's probably not allowed to use 75KHz wide channels on that frequency in US, so it has to be intermodulation from other frequencies.

/Ubbe

In the U.S., 57 kHz subcarrier is also used for RDS.

 

[dlwtrunked]

View attachment 146347

I can tell you that your gain is set too high and therefore what you see *may*I not really accurately represent actual signals.

 

[IC-R20]

I can tell you that your gain is set too high and therefore what you see *may*I not really accurately represent actual signals.

The gain is fine, that's normal for powerful signals to blow the doors off like that and look a lot wider than they really are on waterfall.

 

[Ubbe]

Airspy receivers usually has a noise floor of -100 to -110 and seems to be around that level but there's a strong signal at 460.160MHz that goes up to -35dBm that will usually create havocs in a normal receiver and certainly to a R820/860 chip without any front end filtering. If the OP get that 75KHz wide signal to be received strong again then he can try that suggested test to reduce the front RF gain by 10dB and check if the spectrum also where reduced by 10dB.

/Ubbe