Issues with one channel

Reception, channel detection, network issues, CableCARD setup, etc.
yawlhoo
Posts: 19
Joined: Mon Aug 27, 2018 4:41 pm

Issues with one channel

Post by yawlhoo »

I live in the SF Bay area, and get my OTA TV with an antenna pointed at the nearby Sutro tower (I can see it from my living room window.)

All of the channels I watch broadcast from that tower come in great, but one, KGO-HD Channel 7.1, has issues wherein programs recorded with MythTV are listed in yellow, meaning they are damaged. For sure they are, when viewed the picture at points becomes pixellated, audio smears and there are jumps and elisions.

Looking at the signal quality on the backend with the app hdhomerun_config_gui shows signal strength and signal quality at about 80%, but symbol quality at 100%. From googling I gather this latter measurement is the important one and I should be getting good recordings.

Does this indicate some kind of interference? If so, is there any way to detect and/or eliminate the interference?

NedS
Silicondust
Posts: 1376
Joined: Mon Dec 10, 2018 12:38 pm

Re: Issues with one channel

Post by NedS »

We would like to get some diagnostic data:
  1. Please go to the http://my.hdhomerun.com/ site
  2. Click your HDHomeRun's device ID
  3. If it tells you that a firmware update is available, please install it
  4. Click System Status
  5. Check the Send diagnostic information box
  6. Go back one page
  7. Click Channel Lineup
  8. Click on Detect Channels

Reply back to this post and provide us the device ID of your HDHomeRun and we will check the logs. You can find the device ID at the top of the my.hdhomerun.com web page as well as on a label on the bottom of the HDHomeRun itself.

yawlhoo
Posts: 19
Joined: Mon Aug 27, 2018 4:41 pm

Re: Issues with one channel

Post by yawlhoo »

Device ID: 10725E04

Thanks for responding to my post.

NedS
Silicondust
Posts: 1376
Joined: Mon Dec 10, 2018 12:38 pm

Re: Issues with one channel

Post by NedS »

Signal levels in the log look great for KGO. How often do you see issues/pixelation/etc? It's possible that whatever interference is occurring simply hasn't been captured by the logs yet.

Billi23
Posts: 121
Joined: Mon Mar 20, 2017 8:08 pm
Device ID: 1323AADB

Re: Issues with one channel

Post by Billi23 »

Could be intermittent tower work.
https://www.avsforum.com/threads/san-fr ... t-59978382

See last page of the Sutro Tower newsletter https://sutrotower.com/
"To accommodate some final project cleanup work, some stations will broadcast from their auxiliary antennas intermittently between mid-July and mid-August."

yawlhoo
Posts: 19
Joined: Mon Aug 27, 2018 4:41 pm

Re: Issues with one channel

Post by yawlhoo »

I record the local news on KGO between 5 and 5:30P every night (their weather forecast is always spot on!) A couple of nights earlier this week (Monday and Tuesday?) that broadcast was very messed up. By Murphy's Law as soon as I decided to do something about it (looking up broadcast conditions on rabbitears.info, posting to this forum) things righted themselves.

Maybe it's simply as NedS says, the interference is intermittent.

Later one night when I got a damaged recording I checked the signal as mentioned in my original posting, finding all seemed well, but then a test program recording about this time was also damaged. I don't see how the station shifting to auxiliary antennas could give great signal, but damaged recordings, but who knows.

Thanks to NedS and Billi23 for taking the time to post.

ckwsp101_tv
Posts: 17
Joined: Fri Mar 13, 2015 4:46 pm
Location: marin county , ca

Re: Issues with one channel

Post by ckwsp101_tv »

Posted on another forum

Code: Select all

Weather has not been kind to our efforts. We have postponed the work scheduled for August and will move it into September. We will notify this list as the actual start date gets near. All stations are currently operating on their main antennas.

Cordially,

Raul A. Velez
VP & COO
Sutro Tower Inc.

yawlhoo
Posts: 19
Joined: Mon Aug 27, 2018 4:41 pm

Re: Issues with one channel

Post by yawlhoo »

Tonight (8/1/20) the KGO 7.1 local news from 5-5:30P showed definite pixelation and audio distortions during the recording. Apparently it was not so bad that MythTV marked the recording as damaged (coloring the recording listing yellow), but there definitely were problems.

I wonder if the Silicon Dust staff can see anything in the device log which might reveal what is going on?

yawlhoo
Posts: 19
Joined: Mon Aug 27, 2018 4:41 pm

Re: Issues with one channel

Post by yawlhoo »

Tonight (8/3/20) the KGO 7.1 local news from 5-5:30P was marked in yellow by MythTV, meaning a significantly damaged recording, and it is that, pixelation, jumps, audio smeared out, the whole shebang.

Can the SD staff look at the logs and see whether there is any interference or see what is happening?

jasonl
Expert
Posts: 15302
Joined: Sun Oct 28, 2007 9:23 pm

Re: Issues with one channel

Post by jasonl »

KGO's Sutro Tower broadcast is on channel 7, the lowest frequency on the high VHF band. Any antenna you can fit in a window sucks balls on high VHF, and it generally gets worse the lower you go in frequency, so of course 7 is the worst. Fire up the HDHomeRun Config GUI program, tune to channel 7, and mess around with the coax cable until you find a better position for channel 7. Your typical crappy panel antenna is "designed" to get most of its VHF reception from the coax cable rather than the antenna itself, so how the coax is positioned makes a huge difference ("designed" because proper design is to minimize the impact of the cable). You probably want about a 32" length, and doubling that over might help too. Find something that works and tape it in the window, then run the rest back to the HDHomeRun.

yawlhoo
Posts: 19
Joined: Mon Aug 27, 2018 4:41 pm

Re: Issues with one channel

Post by yawlhoo »

Your post does not seem relevant to my situation: my antenna is a Terk FDTVO omnidirectional antenna mounted on the wall OUTside the window in my house. It gets great reception, most of the time I happily watch perfect recordings of Channel 7, EXCEPT under some circumstances which I attribute to interference. I was under the impression that by checking "send diagnostic information" on the HDHomerun interface, that the folks at SD could read from the logs any such possible interference.

jasonl
Expert
Posts: 15302
Joined: Sun Oct 28, 2007 9:23 pm

Re: Issues with one channel

Post by jasonl »

Nope, definitely relevant to the situation. Still the same old piece of crap antenna that's not properly sized for VHF reception and only mostly works because the signal is strong enough to overcome some of the deficiencies of the antenna. You can't change the laws of physics. Basic antenna design is that optimal performance is achieved with elements that are slightly less than 1/2 the wavelength of the frequency you are receiving. Channel 7 is centered at 177MHz, which is a wavelength of 66.68", meaning you need the antenna to be about 32" across for optimal reception. Specs on that Terk list it as 21"x10", so well below optimal. The coax picks up signals but that results in all sorts of reflections and standing waves and other issues that degrade reception compared to a proper antenna. Messing with the cable is often enough to get a better signal when you're close to the towers, so it's worth trying that vs. going out and buying an antenna that is actually designed for VHF (vs. one that the manufacturer lies and says is for VHF), but sometimes you just need a larger antenna.

NedS
Silicondust
Posts: 1376
Joined: Mon Dec 10, 2018 12:38 pm

Re: Issues with one channel

Post by NedS »

yawlhoo wrote:
Mon Aug 03, 2020 10:23 pm
Your post does not seem relevant to my situation: my antenna is a Terk FDTVO omnidirectional antenna mounted on the wall OUTside the window in my house. It gets great reception, most of the time I happily watch perfect recordings of Channel 7, EXCEPT under some circumstances which I attribute to interference. I was under the impression that by checking "send diagnostic information" on the HDHomerun interface, that the folks at SD could read from the logs any such possible interference.
The logs have been able to capture some more data, and it looks like KGO fluctuates fairly often. The logs don't tell us why the signal fluctuates, only that it does. It's not stable, and I would trust the analysis and advice Jason has mentioned regarding your antenna. It's a UHF antenna, and you can't break the laws of physics.

yawlhoo
Posts: 19
Joined: Mon Aug 27, 2018 4:41 pm

Re: Issues with one channel

Post by yawlhoo »

Well I am a physicist, so I bow to the laws of physics. I will look into the coax/better VHF antenna angle. It is true that Ch. 7 has been bugging me for quite a well, so maybe it's simply a marginal situation which occasionally moves over the margin.

Thanks to jasonl and NedS for taking the time to post their observations.

Billi23
Posts: 121
Joined: Mon Mar 20, 2017 8:08 pm
Device ID: 1323AADB

Re: Issues with one channel

Post by Billi23 »

Isn't KGO Sutro Tower transmitting on RF 12, Virtual 7?
VHF-HI 207 MHz
https://transition.fcc.gov/fcc-bin/tvq?call=KGO

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