Saturday, November 1, 2008

First ATSC transmission from N6QQQ!

I hooked up the stuff I got from Germany today and set it up... And it appears to work perfectly! In fact, the output waveform looks exceptionally clean - just like a real broadcaster! We'll have to see what happens after it gets run through an amp, of course...

The output is -10 dBm, which is less than I had hoped. I will need to boost that, somehow, before feeding it into a DEMI amp. But even so, it was enough to set it running at 420-426 MHz, feed it to my UHF vertical and receive it on the broadcast TV system at -60 dBm! Not only that, but the HDHomeRun actually was able to save the transport stream!

That, unfortunately, is where the good news stops. I don't have the software tools handy to decode that transport stream, probably because I didn't make any attempt to filter the transport stream by program ID or anything.

5 comments:

Anonymous said...

I was able to play it with free software from videolan.org.

Good work!

Nick said...

Thanks! The video you got out should have matched the YouTube clip in the next post. I made that post after I found MPEG Streamclip and was able to use that to get the video and audio out.

Mike said...

Nick,

I have been experimenting with DVB-T on 437MHz, mostly airborne for the past year. The results have been as expected, perfect picture at a 12 mile radius using dipole to 6 db omni on 1 Watt.

I now have an 8VSB setup on the same frequency for some comparison testing. What audio parameters are you using in the Minimod? I have Digital, Stereo, 48KHz sample rate, 256 kBps bitrate with no audio.

73,

KM7MH

Mike said...

Forget my last post, I found that ATSC uses AC3 Dolby audio and the Minimod outputs a standard MPEG2 stream.

73,

KM7MH

Nick said...

Yeah. Some tuners can handle the non-standard MPEG audio and some can't. You're more likely to have success with tuners that are cable ready, as QAM channels sometimes also have MPEG audio rather than AC3. In my experience, CECBs insist on AC3, but tuners built-in to TVs tend to work.