[HN Gopher] Lookup TV Signals by Address
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       Lookup TV Signals by Address
        
       Author : 1970-01-01
       Score  : 20 points
       Date   : 2022-09-27 20:24 UTC (1 days ago)
        
 (HTM) web link (www.tvfool.com)
 (TXT) w3m dump (www.tvfool.com)
        
       | bronco21016 wrote:
       | I used TVFool in the past to setup my current antenna. This post
       | and comment thread led me down the rabbit hole again though as
       | one of my VHF stations has always been a bit flakey and when the
       | wind blows UHF is an issue.
       | 
       | I learned about the difference between UHF and VHF and how
       | vegetation is likely making my UHF channels bumpy when the wind
       | howls. The VHF is likely just an aiming issue.
       | 
       | Anyway, one thing I've always looked for is a reliable way to see
       | how changes in alignment affect the signal in real-time. I
       | discovered Signal GH an app that will connect to your HDHomerun
       | device and provide signal statistics.
       | 
       | Just thought this might be useful for anyone attempting to fine
       | tune their setup.
        
       | naikrovek wrote:
       | This reminds me of a problem that I have yet to figure out - does
       | anyone know of any working GNURadio flowgraph which can decode
       | and display ATSC 1.0 television in real time? I don't want to
       | record now and watch later, for the purposes of this question.
        
         | drmpeg wrote:
         | It's built into GNU Radio. Look in
         | <install_dir>/share/gnuradio/examples/dtv/uhd_atsc_rx.grc
         | 
         | However, it requires quite a bit of cpu and it's performance is
         | terrible unless you're close to the transmitter(s) and have
         | high SNR signals.
        
           | dylan604 wrote:
           | How does that matter in digital transmissions? In analog,
           | with low SNR results, you'd get fuzzy images and other
           | similar issues. In digital broadcasts, you either receive the
           | data stream or not. If you do, you get a signal. If not, you
           | get nothing. I'm not an expert in TV broadcast engineering,
           | but I'm not aware of TCP/IP "did you get that? no? here it is
           | again" type of system as that doesn't work for realtime/live
           | very well.
        
             | supertrope wrote:
             | A radio baseband ASIC is much faster than a software one.
        
             | drmpeg wrote:
             | Performance compared to a hardware demodulator in a
             | television or set top box. A low SNR signal that the
             | hardware demodulator can easily handle may not work at all
             | with the GNU Radio software demodulator.
        
             | naikrovek wrote:
             | I think it has to do with the CPU usage of the error
             | correction. You're right that it either works or it does
             | not, but there is a small bit between working and not
             | working where there is a "can be made to work if the errors
             | can be corrected" region of the signal to noise ratio.
             | 
             | If there is enough CPU after decoding valid frames to error
             | correct invalid frames, and the error correction data is
             | intact enough, AND there is enough CPU to fix the error and
             | decode the frame before the next frame comes in, I imagine
             | that it would succeed. If any of those are not true, it
             | will fail, and require more processing on the subsequent
             | frames until a new I-frame is received.
             | 
             | This is half estimated guess; I don't know the nuts and
             | bolts of how ATSC works, really.
        
       | thakoppno wrote:
       | Any startups working in the OTA tv space?
       | 
       | I can't think of any free signal that is easily consumable as OTA
       | HDTV.
       | 
       | It seems to me like one could leverage the data available
       | nationally to discern developing trends regionally or perhaps
       | determine metro regions that are experiencing growth or
       | stagnation by mining the local news broadcasts or other data.
        
       | threemux wrote:
       | IIRC, TVFool was not kept up to date with the FCC repack station
       | moves. I wouldn't recommend using it as its predictions are
       | likely to be inaccurate. This is a better tool that is
       | continuously updated:
       | 
       | https://www.rabbitears.info/searchmap.php
        
         | brownindian wrote:
         | The source of all other tools:
         | https://www.fcc.gov/media/engineering/dtvmaps
        
       | aidenn0 wrote:
       | Many of these sites are laughably wrong about the high-VHF
       | signals. I lived on a hilltop with direct line of sight to a
       | station on another hilltop 5 miles away. An omnidirectional
       | antenna was worthless at pulling it in; I bought a Yagi
       | specifically for high-VHF, aligned it to the station and that
       | mostly worked.
        
       | graton wrote:
       | I've always used https://www.antennaweb.org/ in the past.
        
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       (page generated 2022-09-28 23:02 UTC)