Mystery signal at 141.540 MHz

[datainmotion]

I posted this originally in the Mil forum, but maybe the experts here are familiar with this...

http://www.radioreference.com/forums...56&postcount=1

FWIW - this was received on a BC780 fed from a simple mobile antenna (150/450/800) mounted 28' AGL

[radiowaves1]

What your more than likely hearing is RTTY or, Radio TeleType of the Amateur Radio kind! Nothing ETish here. Its a common and popular mode of communications. The link to the sample you provided sounds like it to me.

CW, RTTY, Data, MCW,
Test, SSB (Phone), Image



144.1 - 148.0 Mhz

[datainmotion]

Originally Posted by radiowaves1

What your more than likely hearing is RTTY or, Radio TeleType of the Amateur Radio kind! Nothing ETish here. Its a common and popular mode of communications. The link to the sample you provided sounds like it to me.

CW, RTTY, Data, MCW,
Test, SSB (Phone), Image



144.1 - 148.0 Mhz

Wasn't thinking "ET-ish"; more like ISS-ish

[Hooligan]

It sounds nothing at all like RTTY!

Anyone know what the tracking devices using the Orbcomm network sound like?

[radiowaves1]

Oh my, didn't mean to get your panties all in a uproar just because you think it does not sound like what it sounds like to me. So sorry. Forgive me for trying to help. I'll seek your all knowing RFish permission before attempting to try and help someone here with a radio related question again.

Mike / Extra class amateur operator / RTTY contest winner ARRL......

[LarryMax]

Originally Posted by radiowaves1

Mike / Extra class amateur operator......

Who isn't an extra?

Take a break guy, all he said was it didn't sound like rtty. No need to get all huffy puffy about it.

[TerryRR]

I don't usually respond to post that get a little "flaming", but both you guys probably have inteligence to offer to the community. Get over that, and share your thoughts, as professionals. Remember, the Amateur Community has contributed greatly to the advancement of Radio Communications. Having said that, shake hands and move on. The band that this signal resides http://www.rdrop.com/~billmc/freq_list.4
is unpublished. It's most likely government activity. However it apears to be a telemtry signal, possibly a comand and control for either something on the ground or in space. The best way to establish if it's in space is to use cw and track the frequency changes, albeit small, it would indicate a dopler shift, bearing out it is a rapidly moving target. Aircraft will also exhibit this phenomenon, so you can't be certain it is a satelite.

You would need a very sofisticated software / hardware setup to establish exactly what it is. Being non voice and insignificant, spending 5000.00 for a HOKA Electronic - The Netherlands - HF Data Decoder and Analyzer system is your option.
(I'm also an Extra, but my ears are open and my mouth is shut, when I'm learning)

[DaveNF2G]

Are there any MARS services using that frequency range? It seems a bit far from the 2 meter band, but the possibility seemed worth raising (and disposing of if needed).

[tyytor]

I have heard this type of signal used for water control on spinklers and water levels, gate monitors
turning on and off lights usually ....ect gov. related,
the uses are endless our city uses this type singal to regulate flow pumps, gas company's use it all so.
you can call it rtty, data, ...ect. different yes but some times sounds the same to some ears.
you could track it down just by driveing in the direction signal???

[Hooligan]

I think the signal is quite likely SCADA, but SCADA for WHAT is the main question -- building environmental control systems at Buckley AFB, or a satellite uplink/downlink??

I didn't notice any Doppler-shift in the signal so probably not a downlink.

In the USA, that spectrum is allocated for US Gov't Fixed & Mobile, but I think I have some old fact-sheets here somewhere that indicate the old Orbcomm satellite communications system used spectrum in the 140s too.

If that signal is there frequently, Datainmotion should make some motion to Buckley & see if he hears that data in his radio with no antenna on it...

[datainmotion]

I will be down in that area on Thursday. I'll get out on 6th or Jewell Aves. and if I get anything, I'll pull the antenna off the truck and post what happens.

[Hooligan]

By the way, in a 2004 VHF Spectrum Allocation document, the closest listing to 141.540 is 141.5375 -- a channel allocated for "Tactical & Training"

[datainmotion]

Originally Posted by Hooligan

By the way, in a 2004 VHF Spectrum Allocation document, the closest listing to 141.540 is 141.5375 -- a channel allocated for "Tactical & Training"

Generic to Fed?

[Buckskinner33]

Originally Posted by Hooligan

I think the signal is quite likely SCADA, but SCADA for WHAT is the main question

Just one question. What is SCADA?

[Hooligan]

SCADA = Supervisory Control & Data Acquisition -- one way or two-way RF link to remotely control something, possibly receiving feedback (data) from it. Could be something as mundane as a fast DTMF string on an itinerant channel used to remotely activate a sprinkler system in a park to something as cool/complex as remotely activating a store & forward eavesdropping device/sensor via satellite.

[poltergeisty]

Originally Posted by Buckskinner33

Just one question. What is SCADA?

SCADA - Wikipedia, the free encyclopedia


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