Halifax area transmissions spanning 132-144 MHz

[isuse]

I was testing a real-time spectrum analyzer the other day and noticed that somebody seems to be hogging 12 MHz of premium VHF real estate in the area. Given the continuous and uninterrupted levels it would seem to be a broadcast from a stationary transmitter.

I haven't had any luck using google or Industry Canada's Spectrum Direct tools to find users or even equipment that fits this full band. Anyone know the purpose and nature of these transmissions?

The only RR hit I get is for the general designation of that block:

"132–144 MHz: Auxiliary civil services, satellite, space research, and other miscellaneous services"

 

[k1agh]

Well do you have anything in that area that would fit that range? Isnt there a military communications station somewhere in NB or NS?

 

[mmckenna]

Not sure about Canada, but here in the states it's assigned to mostly satellite uses. Could be some broad band uplinks in your area? Lot's of stuff going on there in Halifax.... University research, perhaps?

 

[isuse]

My guess would be terrestrial civil, industrial, or unlicensed/illegal use -- not sat and not mil.

VHF tends to be used for terrestrial broadcast or intermittent applications, and it isn't great for directive antennas, so it's a waste of power for long range broadband comms. LEO satellite command links would be limited duration, so I wouldn't expect to see transmissions droning on for more than 15 minutes.

The navy has local HF TX & RX stations

https://en.m.wikipedia.org/wiki/Naval_Radio_Section_Newport_Corner

https://en.m.wikipedia.org/wiki/CFS_Mill_Cove

and there's a fairly new but smallish igloo on military property in the Halifax area, but it seems hard to imagine it would be operating on VHF let alone spraying energy across the entire 132-144 MHz band.

 

[KevinC]

Or you sure this isn't an image from somewhere else in the spectrum?

 

[isuse]

The Tektronix RSA306 has some spurs but I don't think it's that much of a mess. One clue would be the signal extending across the entirety of a well known band.

 

[KevinC]

The Tektronix RSA306 has some spurs but I don't think it's that much of a mess. One clue would be the signal extending across the entirety of a well known band.

Ok, didn't know what you were using.

How do you like it so far?

 

[isuse]

The user interface on the software doesn't seem particularly efficient, but for the price it's a great tool for my application. 40 MHz of real-time bandwidth is very nice.

 

[ecps92]

There is more use than Sat's in that band here in the US, both LMR and AM for Air

Just looking at Notes, for confirmations from MAINE (could be band opennings) we have in
136-144 Mhz
CBP, FEMA, USN, NCIS, ME-ARNG, CAP, USAF, ME-ANG, USCG, USCG Aux

What is the Signal ? Audio?, Carrier ?, Telem/Data ??

Not sure about Canada, but here in the states it's assigned to mostly satellite uses. Could be some broad band uplinks in your area? Lot's of stuff going on there in Halifax.... University research, perhaps?

 

[mmckenna]

There is more use than Sat's in that band here in the US, both LMR and AM for Air

Just looking at Notes, for confirmations from MAINE (could be band opennings) we have in
136-144 Mhz
CBP, FEMA, USN, NCIS, ME-ARNG, CAP, USAF, ME-ANG, USCG, USCG Aux

What is the Signal ? Audio?, Carrier ?, Telem/Data ??

I agree, but that's a really broad signal for AM air band and LMR. That's some broadband data, which made me thing of the satellites.

Would be interesting to know what it is. If it's continuous (been going on for days), I'd be looking at terrestrial sources. If it isn't something in your house, I'd be looking at either the University or a government user.

 

[mmckenna]

... or cable TV leakage. Channel 16, 17, 18 would span this chunk of frequency.

 

[ecps92]

Ahh, I was only looking at the Spikes vs the underlying Noise ....
True - Cable TV leakage is another source

http://eaglecomtronics.com/Cable_Television_Channel_-_Frequency_Chart.pdf

I agree, but that's a really broad signal for AM air band and LMR. That's some broadband data, which made me thing of the satellites.

Would be interesting to know what it is. If it's continuous (been going on for days), I'd be looking at terrestrial sources. If it isn't something in your house, I'd be looking at either the University or a government user.

 

[isuse]

So the "DPXogram" display on Tek's SignalVu-PC software provides faster updates than the "Spectrogram" display, and it seems to do a better job of documenting the variability in the levels. There are a lot of abrupt fluctuations in power levels, happening over various time scales. The gram in the attachment here shows some spectrum level variations in a 0.5 second snapshot of time, but the fluctuations are quite random - they can be less frequent, more frequent, and exhibit higher or lower levels.

It seems like it might be a communications network.

 

[isuse]

Non-local signal, same spectrum about 5 km away from the first site.

 

[mmckenna]

Time to grab a directional antenna and do some hunting. Unlikely a simple cable TV leakage issue if it's covering that sort of area. Still seems like a data stream/broadband emission.

 

[hfxChris]

Is this constant? I'm not seeing anything at all right now. I am also just using an RTL-SDR I dug out of the drawer, but if it's that noisy I should see something.

 

[isuse]

Is this constant? I'm not seeing anything at all right now. I am also just using an RTL-SDR I dug out of the drawer, but if it's that noisy I should see something.

Yes, it has been constant. It was showing up yesterday but I don't have the equipment with me today.

You could struggle to perceive it with the limited bandwidth on the RTL-SDR but, assuming that receiver isn't self-noise limited in that band, you should be able to make relative power measurements of the "noise" floor at a series of frequencies (tuning it from 125-150 MHz in 1 MHz steps) and be able to obtain the same general conclusion as you might reach with the broaband spectral display on the RSA306.

I shot some video (sorry about the quality) the other day which might give you a better idea of what this stuff sounds like when tuning up on a narrowband voice channel.

https://www.youtube.com/watch?v=ETMn_T_lnWQ

 

[hfxChris]

Yes, it has been constant. It was showing up yesterday but I don't have the equipment with me today.

You could struggle to perceive it with the limited bandwidth on the RTL-SDR but, assuming that receiver isn't self-noise limited in that band, you should be able to make relative power measurements of the "noise" floor at a series of frequencies (tuning it from 125-150 MHz in 1 MHz steps) and be able to obtain the same general conclusion as you might reach with the broaband spectral display on the RSA306.

I shot some video (sorry about the quality) the other day which might give you a better idea of what this stuff sounds like when tuning up on a narrowband voice channel.

https://www.youtube.com/watch?v=ETMn_T_lnWQ

Yeah it samples about 2 MHz of spectrum, so stepping up and down the band I should see something... but I don't.

 

[isuse]

I'll try evaluating noise floor at my location with FCDP+ and RTL-SDR.