Las Vegas - Channel 29 or Channel 1?

[kingcoldcuts]

Kind of a weird, possibly niche issue...

Some time back I posted about intermittently receiving "Unable to Play Channel" messages when tuning Vegas ATSC 3.0 channels. I thought it had been worked out, but then the problem returned. I just decided to deal with it.

Last weekend I decided to mount my outdoor antenna in a different location. I downloaded a third party app (iphone) to help me monitor signal signal strength as I made adjustments to the direction. I noticed that when tuning in ATSC 3.0 channels, sometimes the tuner uses channel 29, and sometimes it displays as channel 1. When using channel 29, the signal constantly goes in and out. Most times it fails and displays the error message on the TV. However, when using channel 1, the signal is rock solid. I can't seem to force it to use one or the other, and I have no idea why it goes between the two.

It would be great if the tuner just used channel 1, but what is channel 1 anyway? Surely it's not actually channel 1? Hoping someone can enlighten me as to what is happening here.

Thanks!

KCC

[kyl416]

Since Vegas is the home of the NAB and CES shows several broadcasters occasionally get experimental licenses to test new technologies. i.e. From 10/8-11/17 KSNV has an experimental license to test mobile reception with Hyundai on UHF 33. And if KVCW's UHF 29 signal is like Sinclair's other ATSC 3.0 stations they're likely testing some radio channels on the more robust but lower bandwidth PLP layer while all the actual channels are on the less robust but higher bandwidth PLP layer.

There's no such thing as RF 1 for OTA, and no one in Vegas is listed as using virtual 1 officially, so Silicondust would need you to do a scan with diagnostic information enabled to figure out where that "1" is coming from. They could also map listings to it so you can record on "1", but if it's like Sinclair's previous tests, the content on it can change without notice and it will likely go away whenever they finish the test.

[kingcoldcuts]

Thanks!

I am aware of the tests. This isn't related to any of those. This has been going on for about 2 years with a brief respite right after CES last year. The difference is I wasn't using a third party tool to monitor the signals. I suspect it has something to do with the way the lighthouses are configured here, but I'll wait for someone from SD to jump in.

KCC

[jasonl]

I would assume that this is a bug in the third party app you're using, probably that it is parsing the "ch=atsc3:587000000:1" bit of the tuner status as channel 1 instead of PLP 1 on 587 MHz (channel 33).

[kingcoldcuts]

I have reached out to the developer.

However, when tuning an ATSC 3.0 channel, I can see that PLP0 fails and presents an error message. PLP1 successfully tunes the channel. It seems random as to which PLP the tuner attempts to use.

Is there a way to force the Flex 4K to tune only using PLP1?

Thanks,

KCC

[jasonl]

The HDHomeRun automatically tunes whichever PLP is required (including multiple PLPs simultaneously) for the particular virtual channel number being accessed.

[kingcoldcuts]

Except for when it doesn't...

This is something I worked on with @Nickk in December 2023. There used to be a forum thread. I assume there was a purge? I also no longer have access to the PMs that were sent.

So in lieu of the Flex 4k automatically tuning whichever PLP is required, is there a way to force it? Because at this time, the behavior is not as expected. At least, not with my particular unit.

Thanks!

KCC

[fri1038sd]

Use the Windows version of hdhomerun_config_gui to tune a particular PLP. It's in SD's support->downloads area. The linux version doesn't have the PLP check boxes, last I checked. Probably doable with the command line hdhomerun_config, too.

What you are chasing could be an unviewable data stream or some inactive demo if nothing shows up.

WNUV in Baltimore had a recent problem where it was necessary to manually tune PLP1 to see the program list. Fixed now.

[kingcoldcuts]

Use the Windows version of hdhomerun_config_gui to tune a particular PLP. It's in SD's support->downloads area. The linux version doesn't have the PLP check boxes, last I checked. Probably doable with the command line hdhomerun_config, too.

What you are chasing could be an unviewable data stream or some inactive demo if nothing shows up.

WNUV in Baltimore had a recent problem where it was necessary to manually tune PLP1 to see the program list. Fixed now.

Appreciate everyone's replies!

To clarify:

Example: When I try to tune in NBC - Channel 103.1, sometimes it gives me the "Unable to play channel: No Video Data" message. If I then tune in a different channel, ATSC 1.0 or 3.0 (it doesn't seem to matter), then return to 103.1, it *might* tune the channel properly. If it does not, I have to try the process again until it does. This is for all unencrypted ATSC 3.0 channels in Las Vegas.

The only discernible different I can see is when I use Signal GH - which is how this thread started. When I tune 103.1, and Signal GH shows Channel 29 is trying to tune, the Signal Quality bounces from 0-100 and then fails. But if the tuner tries to tune in Channel 1, everything works as expected.

It's probably time for some screenshots. Please see the following:
https://1drv.ms/i/c/844f4e8298117e6b/Eb ... Q?e=4j1pbp
https://1drv.ms/i/c/844f4e8298117e6b/ES ... g?e=QdhiHc
https://1drv.ms/i/c/844f4e8298117e6b/EY ... g?e=EgcnpU

I have set this file share to expire in 1 week.

I have seen the check boxes in the config-gui before, but if I remember correctly, making manual changes were not persistent, I believe by design.

Thanks again, all!

KCC

[kingcoldcuts]

I turned on diagnostic information, recreated the issue, and turned it off again.

Device ID: 10A64085

KCC

[fri1038sd]

Fair enough, though I think hdhomerun_config_gui could give you additional insights as to PLP configuration and reception levels.

In my experience, a slow home network can cause the 'no video data' message. Or when there is actually no data in the signal, as hdhomerun_config_gui would show in the Program pull down menu, if you tried to View a program/subchannel.

[signcarver]

Those pictures can be meaningless when it comes to atsc 3.0 and certain plp configurations as some may go up and down under normal conditions. What you need to do is look at it in config_gui check each plp individually (including looking at the channel list drop down and see which may have no data on a particular plp) and then see which ones can also work together. I also suggest for your own troubleshooting that you keep levels below 100% in strength as you don't know how much above 100 it is which can also cause the issue in question. I also suggest use of an lte filter (particularly when you have stations with a strength of 100%).

When you are viewing with the app, it is always from the same source "for days" unless you happen to run a scan inbetween (which will happen every few days) as when you request it, it tunes what is in its tuning table so would not just happen to come back working as you described of being from "1" vs "29". Check the lineup.json with the tuning parameter ( http://hdhomerun.local/lineup.json?tuning ) as that shows what the request is using.

The symptom for the app you described can have many causes many of which are not signal related at all, particularly if it keeps working for quite awhile once tuned (not saying the error won't/can't come up again after a few minutes signal related or not).

[kingcoldcuts]

UPDATE: I now think you were talking about the HDHomerun app, and not the 3rd party app. If that is the case, the next sentences lines do not apply....

Forget about the app for now. It was just something that tipped me off to investigate the PLPs used. I see your everyone's point about the app.

My LAN is hardwired and iperf reports a nearly fully satiated 1gbps connection. I have had an LTE filter and FM filter inline for years. The antenna is 21ft from the box. I am using quad-shielded, solid copper coax for the run. I am not having signal issues of any kind, whether above or below 100%. No attenuator makes a difference either. Hope that clears up some of the assumptions.

So I launched homerun_config_gui and tuned in channel 103.1 using the HDHomerun app on my Nvidia Shield (even though this happens regardless of device - STB, PC, Mac, Mobile). The tuner tried to tune using PLP0 qam16 (red in color), neither checkbox was filled, the Signal Quality bounced between 100 and 0 for about 5 seconds before failing to lock onto anything and falling back to Channel 0. The screen shows the No Video Data error.

I immediately tuned Channel 108.1 using the app on the Nvidia Shield. The channel immediately tunes using PLP1 qam256 (green box), the checkbox for PLP1 is checked (PLP0 is empty). I cannot change the state of the checkboxes (but also wouldn't want to as this is the behavior I want!). All stats are 100 across the board. The signal is perfect. The picture is perfect. The sound is as expected.

I immediately change back to 103.1 and it tunes in fine, but this time the PLP configuration is PLP1 qam256. So back to 108.1, and this time the tuner uses PLP0 qam16, and fails to tune - No Video Data error.

This all literally happened in a span of a few minutes, but has been going on for well over a year. As I mentioned above, I had a long thread regarding this last year, and worked with Nickk to try and resolve. Every time I try to tune an ATSC 3.0 channel it is seemingly random as to which PLP it chooses. Nickk mentioned last year that maybe the local area channels here are doing something funky. I just want it to always use PLP1 qam256 as that's the one that works without fail.

Now what?

Thanks!

KCC

[danieljlevine]

Is there a way for me to reproduce your results on ATSC 3.0 channels that report no video data in my area if I don’t have an Nvidia Shield? I have a FireTV 4K for the HD Homerun App. I also run HD Homerun and Channels on iOS and iPadOS.

[fri1038sd]

...
Now what?
...

Funky.

Using the View button in config_gui to tune the channel, instead of the Shield and App, do you see the odd PLP selection behavior?

Probably not relevant, but I wonder if this station is configured as LDM. Look for "layer=enhanced" and "ti=cti" in the PLP parameters shown in config_gui. If it's like WIAV-CD in DC, both PLPs need to be tuned in to view a channel.