Single Channel Issue

Have Tablo connected to external antenna with splitter running to tv as well. Have done channel scan and got everything I was expecting with five “bars” showing on the channel lineup. However I have had repeated failed recordings on one channel. This channel also has five “bars” and shows up fine when tuned directly from tv. However I can’t get it to show the channel on live tv “player error unable to tune to channel . This is usually caused by poor reception”. When I rescan the channel disappears from lineup but again still tunes fine directly on tv outside tablo environment. This is one of my main channels and I have never had a live viewing issue with it before I got the box. Any suggestions?

@MelC If the you’re receiving a reception error from the Tablo on live TV, and it doesn’t show up on a Re-scan, it’s possible the Tablo can’t tune to it; the channel may be on the wrong side of the ‘cliff’ for the Tablo.


Could you try removing the splitter and giving the Tablo a direct connection to your antenna instead? Just to see if you can pick it up.

Removed splitter and plugged coax in directly. Still not picking it up although it is picking up another version of same station but with only one red “bar”. The channel I want and should get is 57-1. The channel that is now showing up but not with any quality is 56-257.

What do you mean by cliff?

@MelC 


There are a few conditions that can cause the Tablo not to receive a channel when the TV can. ATSC HD digital TV reception is not like the old analog TV whereby the picture gets gradually worse as the signal weakens. For digital, the relationship between the signal level and the picture quality is more like a cliff. The picture will look perfect until the signal weakens to a point where all of a sudden the video is virtually unwatchable (falls off a cliff). The difference in signal between a great picture and none at all can be very small. 

In engineering terms, we determine signal quality by measuring the ratio of the signal we want in relation to the noise. This is called the Signal to Noise Ratio (SNR). As you get more distant from the broadcast tower, the signal level drops and the noise increases and therefore the SNR declines. At a certain value (typically around 14db or so) the SNR is too low to extract the actual HD video from the noise and the bit error rates and packet error rates rise dramatically causing dropouts or break up of the video. This is where the cliff function comes in, at 15 db SNR the video may look great but at 13 db SNR the picture could be unwatchable. There is a very narrow range between good and bad. In this range you may see lots of drop outs and video corruption. 

The Tablo has two tuners, so we need to split the signal internally which causes a 3db drop to each individual tuner compared to a TV which only has one Tuner. We try to compensate for this with a low noise amplifier, so the drop in SNR is much less than 3db. However the amplifier also increases the noise which will degrade the SNR slightly. 

@MelC


I had the same issue on one of my VHF channels (local ABC affiliate) but it was very intermittent and almost time-of-day related.  I tried removing my splinter, scanning channels, everything I could think of and it would still sometimes come in poorly.  When i tried my TV tuner, the signal improved slightly but would still have problems at the same time as the Tablo.  I looked at the signal strength at these times and  it went from 5 bars all the way down to 1-2.  

I did some more research and found that the particular station is hard to pick up in my area of town.  I just purchased a 15dB preamp and installed a week ago to boost the signal and so far so good.  You might look into the same option if you are on the edge of picking up the signal.

It is not only the strench of the signal that count but the quality, it is possible that you get the signal from a direct path plus the signal that is reflected by object, in that case the signal can be strong, but it could come and go.

I remember watching TV with the small internal antenna when it was analog, the view would get better and worse as a plane was flying over. The difference with digital is that it goes on and off


@Informel Well said :slight_smile: