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Old 09-01-2016, 04:23 PM
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ATSC video in 1GHz+

I was going through the spectrum last night, and noticed something odd. In 1GHz+, I'm finding ATSC video signals. I can identify them easily by the ATSC pilot tone. But here's the thing, here in America, ATSC is assigned to regular TV frequencies, mostly UHF. UHF ends at around 700MHz now (channel 51). Even then, UHF channel 83 would have been ending at around 890MHz. Not to mention, it's not using 6MHz bandwidth, it's using 12MHz.

So what ATSC signal is this? None of my TV's or converter boxes can tune up to this frequency to receive it, even though it's a nice and strong signal too.

Here's a picture of the beginning of the signal, showing the pilot tone visible.
http://i.imgur.com/CFLIAbL.png
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Old 09-01-2016, 04:30 PM
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23 cm ham band transmissions? Are some now using atsc??

https://en.m.wikipedia.org/wiki/23-centimeter_band

Or perhaps just harmonics?

jr
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Old 09-01-2016, 04:40 PM
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I was originally thinking harmonics, but I have ruled it out by carrying the radio outside and using a simple dipole. It's weaker, but there. Also, the signal comes and goes. Shows up on other frequencies at times, and it will do this even if nothing in the antenna alignment, or anything else change.

You bring up hams. I was thinking maybe? But, why 12MHz bandwidth? As of right now it's completely gone, and no longer on this frequency.
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Old 09-01-2016, 05:03 PM
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Is the digital reference carrier approx 0.310 mHz above the bottom edge of the transmission spectra, as per normal broadcast atsc tv?

jr

Last edited by jr_tech; 09-01-2016 at 05:12 PM.
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Old 09-01-2016, 05:28 PM
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Yep, it would appear that way, and the frequency moved somewhere else.

Lower Edge: http://i.imgur.com/Ym1GUji.png
Pilot Tone: http://i.imgur.com/5fdrOPq.png
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Old 09-01-2016, 05:44 PM
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That would appear to rule out 2nd harmonics of a broadcast atsc tv station, as I would expect the carrier to be 0.620 above the bottom edge.
For grins, I just tuned around the second harmonic region of several very strong local channels using my Icom 8500 and found nothing... I suspect that the broadcast channels are fairly clean.
This is a real head scratcher, but I am leaning toward ham experimental transmissions.

jr
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Old 09-01-2016, 05:51 PM
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I wish I was able to get a TV to tune to it, it would be real interesting to see what is actually being transmitted.

I'll have to go with experimental too then, especially since it's changing what frequency it's showing up on.
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Old 09-01-2016, 06:18 PM
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Well, looks like I should have checked with the ARRL first.

http://www.arrl.org/band-plan

"ATV Channel #1".

Well, looks like that solves that mystery. I just didn't know hams were using ATSC now. I thought they still used NTSC.
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Old 09-01-2016, 06:28 PM
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The 12 MHz bandwidth is still mysterious. I wonder if this is being done with some kind of software-defined radio now?
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Old 09-01-2016, 06:28 PM
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A google search for "ham atsc tv" will turn up a few hits, such as this:

http://www.tvtechnology.com/broadcas...inition/277772

Apparently there are no set standards yet, so 12 mHz width might be used in your area.

I am going to check 23 cm periodically to see if anything turns up in the west coast region.

jr
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Old 09-01-2016, 06:41 PM
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A simple converter to beat this down to low UHF might be fun to try. The article mentions relays from California to Arizona - I wonder if any of this gets into the Tucson area.
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Old 09-01-2016, 06:54 PM
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Quote:
Originally Posted by old_tv_nut View Post
A simple converter to beat this down to low UHF might be fun to try.
Oh yea, I need to do that.
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Old 09-01-2016, 06:59 PM
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Fascinating!

Two ways you may be able to receive it: 1.) find/modify/create software that takes the data from your SDR and converts it into A/V data your PC can handle. 2.) Try heterodyning the carrier down into the OTA DTV band and feeding it into a conventional DTV box.
EDIT: I see Old_TV _nut beat me to #2 while I was reading that article.
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Old 09-01-2016, 07:09 PM
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Possibility of using the SDR to decode?

http://www.rtl-sdr.com/watching-atsc...and-gnu-radio/

jr
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Old 09-01-2016, 07:43 PM
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My home made SDR only has a maximum of 3MHz bandwidth, but only 2MHz reliable without loosing information. I just don't have enough grunt on a home made SDR.

I'm gonna go with old_tv_nut's idea. Something like that I can easily interface to a DTA, and feed it right to my TV set in my bedroom, or even my portable ATSC TV.
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