Saturday, 7 December 2013

Improvised DVB-T test instrumentation

Improvised DVB-T test instrumentation

My last post was on snooping on DVB-S signals from satellites. I found some useful software to do that, Crazyscan and Blindscan. However, the author of Crazyscan also wrote Crazyscan 2 for DVB-T but needs specific TV hardware:

I ordered a TBS 6220 (DVB-T) (~$100) as well a TBS 6925 (DVB-S) (~$300), both pci-e cards, direct from the manufacturer . With courier delivery, they arrived within a week.

Setting up the TBS 6220 is straight forward and works well as a TV card with DreamTV; mainly to confirm that the device works. I put both cards in and software for both, but things got messy. Removing the TBS-6925 and its software, including auto start programs, fixed everything. I need to walk before I run.

My interest is with Crazyscan2. Setting it up is easy, just putting all the needed files in the same directory.

The result is amazing: a scan over 1 GHz at 1 MHz increments, albeit for DVB-T stations and slow; well seconds! I am used to the BladeRF. But they are two different animals.

The screen shot the VHF/UHF spectrum from my TV antenna aimed at Mt Tamborine. The DVB-T stations can be seen the left side of the shot.

However, clicking in the middle of the peak of a DVB-T signal gives me what I have been chasing, the constellation diagram! It also gives other data for the signal down the bottom of the slot.

The constellation diagram gives an idea of the quality of the signal and any issues with modulation, amplifiers and antenna.

So for about $100 for the card and a modern computer, I finally have a means of checking my DVB-T TX, hopefully the subject of the next post.

No comments:

Post a Comment