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

23 cm ham band transmissions? Are some now using atsc??

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

Or perhaps just harmonics?

jr

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.

Is the digital reference carrier approx 0.310 mHz above the bottom edge of the transmission spectra, as per normal broadcast atsc tv?

jr

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

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

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.

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.

The 12 MHz bandwidth is still mysterious. I wonder if this is being done with some kind of software-defined radio now?

A google search for "ham atsc tv" will turn up a few hits, such as this:

http://www.tvtechnology.com/broadcast-engineering/0029/ham-tv-operators-go-high-definition/277772

Apparently there are no set standards yet, so 12 mHz width might be used in your area. :scratch2:

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

jr

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.

A simple converter to beat this down to low UHF might be fun to try.

Oh yea, I need to do that.

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.

Possibility of using the SDR to decode?

http://www.rtl-sdr.com/watching-atsc-tv-with-an-sdrplay-sdr-and-gnu-radio/

jr

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.

Will be interesting, but I suspect that the channel width will be a serious problem on a standard set... wonder what you will see. :scratch2:

I would suggest getting on a busy repeater and asking around... likely you will find somebody that knows all about these transmissions.

jr

Will be interesting, but I suspect that the channel width will be a serious problem on a standard set... wonder what you will see. :scratch2:

I would suggest getting on a busy repeater and asking around... likely you will find somebody that knows all about these transmissions.

jr

I'll do that tomorrow when I'm not buzzed from beer. ;) I have a sailors mouth when I drink, best I not get on the air.

What would ham radio enthusiasts want with video transmission?

I picture it as being like YouTube for old people.

I'd watch it.

And I ain't old, and am already interested in this.

A little help for a non-ham who is getting hit on my wireless cams at my ballpark. I looked farther down in the AARL list and found 5 Centimeters (5650.0-5925.0 MHz) which is in the unlicensed space my cams operate at. We are not broadcast so we cannot get a licensed space.

Occasionally I will get a pulsing (every 4 seconds or so) carrier that hits my rxs. At first I thought it was airport terminal radar but it comes and goes and they are lower anyway. My rx units can show me the spectrum on any given channel I use and I can see the pulse but have no idea what it is. Could it be something from the chart? I operate on 12 possible channels between 5700 and 5975. 25 meg per channel for HD-SDI video and audio. The pulse seems to cross several channels at a time.

Is this an unlicensed space for hams also? Mystified here.

If this needs a new thread please proceed. Dave A

If I'm reading this page correctly
https://en.wikipedia.org/wiki/U-NII

the table "5 GHz (802.11a/h/j/n)" says frequencies in this range are approved for 5 GHz wifi (your application), which says to me that someone else may be using it for a purpose other than your cameras. What that would be is hard to guess, but a regular pulsing sounds like maybe some sort of wireless link keep-alive. I once had a video repeater that shared the band with my cordless phone (2 Ghz? 2.5 GHz? don't remember now), and the phone would produce a repeating pulse in the video, making the video useless.

Wayne...I looked at that too. Sysco has a warehouse near me and they do use 5gig wifi. Amazingly they are 2000' away and the signal is strong here. I think 5gig can have a higher tx power. I can see it on my wifi sniffer on my phone. But they are 24/7 and this comes and goes and the signal is wide enough to cover several channels at 25meg each.

New wide channels in that range?

http://www.nhtsa.gov/DOT/NHTSA/NVS/Public%20Meetings/SAE/2016/SAE%20Government-Industry%202015%20(Fessmann).pdf

jr

I just didn't know hams were using ATSC now. I thought they still used NTSC.
I am a long-time operator of TV over ham radio (ATV, amateur television). One of the joys of ham radio is that we are not limited to specific standards for most of our transmissions, so in the case of TV signals, hams have used NTSC (AM-mode), as well as FM-mode NTSC, and several digital modes. ATSC is pretty rare in the ATV world, partly because transmitting equipment is expensive and/or hard to obtain. Other digital modes (DVB-S, DVB-T, even QAM "digital cable" mode but put on the air) are more common.

If that 12-MHz ATSC signal was indeed an ATV station, the bandwidth was probably not intentional; it may be a type of intermodulation problem that happens in the station's amplifier(s).

What would ham radio enthusiasts want with video transmission?

I picture it as being like YouTube for old people.
I had to laugh at that comment! (-:

ATV operators do things such as relaying video from a disaster site to an emergency operations center, or behind-the-scenes activity from the Rose Bowl parade. We also just show off our latest projects (such as when I linked my own signal into my restored RCA 8TS30, then pointed a camera at it on the air), or scenes of our ham stations, cats in the house, have "tie-dye shirt nights" and many other activities. Lots of fun.

I am a long-time operator of TV over ham radio (ATV, amateur television). One of the joys of ham radio is that we are not limited to specific standards for most of our transmissions, so in the case of TV signals, hams have used NTSC (AM-mode), as well as FM-mode NTSC, and several digital modes. ATSC is pretty rare in the ATV world, partly because transmitting equipment is expensive and/or hard to obtain. Other digital modes (DVB-S, DVB-T, even QAM "digital cable" mode but put on the air) are more common.

If that 12-MHz ATSC signal was indeed an ATV station, the bandwidth was probably not intentional; it may be a type of intermodulation problem that happens in the station's amplifier(s).

Yea the most I've done is AM mode NTSC at 70cm, because I can pick it up on any CATV ready set in CATV mode.

I actually didn't even know an FM mode existed for NTSC, now you have me more interested than ATSC, because I might be able to transmit this. *goes to research this*

FM TV can look much nicer than AM NTSC, and there are inexpensive synthesized transmitter and receiver boards available from a Web site called hampubs.com (under $100 each if I remember). They operate on the 900 MHz and higher bands; FM TV is too wide a signal to be used on the lower-frequency ham bands.

Also, when you need an amplifier for FM TV, any "class C" one will work fine, so things are less picky than when setting up an AM ATV station.

FM video is used for videotape, like that used in VCRs. Ham FM video might use chips intended for converting analog baseband video to FM to the tape head, and from the tape head back to analog baseband video.

I would think as a ham, we would naturally gravitate to DVB-S over 1.2 gig since all it takes is a fta satellite receiver and a pre-amp on the antenna, plus a lot of European hams are working on modulators, amps, etc.


It won't take long for DVB-ATV or some other digital format to come to prominence.

Indeed, DVB-S is being used for Digital ATV on the 23cm band (1240-1300 MHz) exactly as you described. No preamplifier needed, even, with the newer DVB ("MPEG FTA") satellite-TV tuners.