# Gr-atsc related question **URL:** \ **Category:** GNU Radio\ **Created:** [September 15, 2012, 12:02am UTC](https://www.ruby-forum.com/t/gr-atsc-related-question/222922 "2012-09-15T00:02:32Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\ **Post date:** [September 15, 2012, 12:02am UTC](https://www.ruby-forum.com/t/gr-atsc-related-question/222922/1 "2012-09-15T00:02:32Z")
Hi, I am new to gnu radio/usrp. I am trying out digitial TV application gr-atsc. I have a USRP N210 with a basic omnidirectional antenna. I checked local digital TV stations and found (from Internet) that there is one at 603.25 MHz (UHF channel 36) and the station is listed to be about 14 miles from here. When I run uhd\_fft to receive the channel, I do not see any signal. I used a hardware oscilloscope to scan the UHF band, but could not find signal anywhere. Could it be because I do not have a good antenna (I have only basic omnidirectional antenna which looks like a 0.75 foot rod; sorry I do not have much communication engg background). Now, even without any TV signal, should the gr-atsc application Work? It is ok if it shows me a black screen from the mpeg file. But when I run the five python scripts (interp\_short.py, xlate.py etc.), The mpeg file generated is of zero size. So I modified the python scripts to write to file (instead of fifo). What I found was that after runnin “btl-fsd-py”, its output file is of size zero (other scripts before it generate file of huge size). What is the problem here? Thanks. -Anirudh ---
**Author:** ![SahooS\_Anirudha](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a87d85/32.png) [@SahooS\_Anirudha](https://www.ruby-forum.com/u/SahooS_Anirudha)\ **Post date:** [September 15, 2012, 4:47pm UTC](https://www.ruby-forum.com/t/gr-atsc-related-question/222922/2 "2012-09-15T16:47:27Z")
On Fri, Sep 14, 2012 at 5:41 PM, Sahoo, Anirudha [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > there is one at 603.25 MHz (UHF channel 36) and the station is > > The mpeg file generated is of zero size. So I modified the python scripts > Thanks. > > -Anirudh Anirudh, If you can’t see a signal and there is nothing to demod, then the mpeg file size should be zero. ATSC has digital frames that are used in locking and syncing with the signal. If the receiver can’t find these bits, it has no idea how to frame the mpeg, so it doesn’t produce anything. What kind of daughter board are you using with your USRP? Have to adjusted the gain to see if that helps? Any other stations around you that you can try, instead? You should also be able to find a ATSC amplifier that you can put between your antenna and USRP if you are still having trouble getting a signal. Tom ---
**Author:** ![SahooS\_Anirudha](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a87d85/32.png) [@SahooS\_Anirudha](https://www.ruby-forum.com/u/SahooS_Anirudha)\ **Post date:** [September 17, 2012, 12:14am UTC](https://www.ruby-forum.com/t/gr-atsc-related-question/222922/3 "2012-09-17T00:14:53Z")
Thanks Tom for the prompt and helpful reply. I am using SBX 400-4400 MHz Rx/Tx daughterboard. * * * From: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [removed\_email\_address@domain.invalid] On Behalf Of Tom Rondeau [removed\_email\_address@domain.invalid] Sent: Saturday, September 15, 2012 10:46 AM To: Sahoo, Anirudha Cc: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Subject: Re: [Discuss-gnuradio] gr-atsc related question On Fri, Sep 14, 2012 at 5:41 PM, Sahoo, Anirudha [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > there is one at 603.25 MHz (UHF channel 36) and the station is > > The mpeg file generated is of zero size. So I modified the python scripts > Thanks. > > -Anirudh Anirudh, If you can’t see a signal and there is nothing to demod, then the mpeg file size should be zero. ATSC has digital frames that are used in locking and syncing with the signal. If the receiver can’t find these bits, it has no idea how to frame the mpeg, so it doesn’t produce anything. What kind of daughter board are you using with your USRP? Have to adjusted the gain to see if that helps? Any other stations around you that you can try, instead? You should also be able to find a ATSC amplifier that you can put between your antenna and USRP if you are still having trouble getting a signal. Tom