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Author Topic: What digital mode is this?  (Read 1720 times)
KE7IZL
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Posts: 47




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« on: August 02, 2011, 01:27:23 AM »

It seems to be a packet based digital mode. By its packet length it is definitely closer to Pactor ARQ, not Amtor ARQ. However it lasts a bit longer than Pactor. Also it it has an ACK waiting period that's much longer than ones like Amtor or Pactor who's waiting slot is barely wide enough to fit the ACK reply in. Several such reply packets could fit into the wait period in this mode. My first thought was maybe packet radio, but HF packet is 300 baud, but this sounded slower, like Pactor-1 ARQ in 100baud mode. So I took out MultiPSK and tried to decode it with it set to Pactor, but (as expected) it didn't decode it. The packet was just too long for a standard Pactor packet.

Also it wasn't in a ham band, but had a center audio frequency about 1.4kHz when my Icom PCR1000 was set to USB and tuned to 13.055MHz (putting it's center RF at 13.0564MHz, well outside any ham band). Thus it's likely to be for some professional communication equipment, and may not be a standard mode for ham operation.

Here I've posted a download link to a zip archive containing three MP3 files. One is a recording of the signal I am talking about, and the other 2 are Amtor ARQ and Pactor-1 ARQ (which I downloaded from a radio sounds site, and then trimmed to make a reasonable length). These 2 files are just a reference.
http://www.mediafire.com/?h1tn9xnbk58dco6

And here's a zip archive containing the spectrograms of each of the 3 signals that were in the above zip archive.
http://www.mediafire.com/?9lm5l9y0agx730t


If someone can tell me what this signal is, I'll be really happy. I've been hearing it now for years on my ICom PCR1000 receiver and have no clue what it is, and that's just driving me nuts.
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AD6KA
Member

Posts: 2232




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« Reply #1 on: August 02, 2011, 04:41:07 AM »

How often do you hear it? An particular days?
What UTC time(s)?
You might consider posting this on one of the SWL
UTE Monitoring Web Sites or blogs. Some of those guys
are very knowledgeable and love a challenge.
Google will help you find these groups.
GL ES 73, Ken  AD6KA
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KE7IZL
Member

Posts: 47




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« Reply #2 on: August 02, 2011, 12:09:10 PM »

How often do you hear it? An particular days?
What UTC time(s)?
You might consider posting this on one of the SWL
UTE Monitoring Web Sites or blogs. Some of those guys
are very knowledgeable and love a challenge.
Google will help you find these groups.
GL ES 73, Ken  AD6KA

I live in Seattle, Washington. I often here these transmissions. You can hear them every day.They often fade which suggests ionospheric distortion of the signal, which means I'm not receiving it line-of-sight, but rather on ionospheric bounce, which means the source of the signal is quite some distance away, not right here in Seattle. Anyone else on these forums ever hear this transmission before?
The specific instance of this transmission that I heard last night was at 12:20AM Pacific Daylight Time.

I just looked at this FCC frequency table http://transition.fcc.gov/oet/spectrum/table/fcctable.pdf (accurate as of June 2 of 2011) and it seems that signal is in a band that is used in the US and internationally as a "maritime mobile" band. I often find strange signals such as this in various HF maritime bands.

.:Update:.
I just tuned there again right now (13.055MHz on USB) and the signal is still there. Right now it's 12:18PM Pacific Daylight Time.
« Last Edit: August 02, 2011, 12:18:51 PM by KE7IZL » Logged
KE7IZL
Member

Posts: 47




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« Reply #3 on: August 05, 2011, 07:26:05 PM »

FINALLY figured it out from help at RadioReference.com
It's something called GW Dataplex (aka GW Pactor). It's transmitted by Global Wireless communication hardware.
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