[Discuss-gnuradio] No horizontal sync with ntsc tv reception

[Nirali Patel]

Hi,

 

I am working on ntsc tv reception as a precursor to hdtv reception. I am using usrp_rx_cfile.py to capture samples to a file from the TV_RX board and then playing back using usrp_tv_rcv_nogui.py. The picture displayed does not seem to have horizontal sync (picture keeps moving from left to right). I have tried setting different decimation factors, the best I can use without overruns is a factor of 8 and the picture still rolls in horizontal direction. My understanding was that the decimation factor would only affect the horizontal resolution not the ability to sync, but I could be wrong. The commands that I use for capture and playback are:

./usrp_rx_cfile.py –R B –d 16 –f 531.25M –s tv1.out

./usrp_tv_rcv_nogui.py –f 531.23M –n –i tv1.out sdl

 

where 531.25 Mhz is the picture carrier of the ntsc channel with lower band edge at 530Mhz.

I have also tried using –f 533M to set the tuning frequency to centre of the band but no significant change in picture sync.

If anyone has experienced similar problem I would appreciate the guidance. Does the antenna setting have any influence on h-sync? My office is in the interior of the building so would it help to move towards the exterior?

 

Thanks in advance for any help.

 

Nirali Patel