Wildly fluctuating Symbol Quality on some channels

Reception, channel detection, network issues, CableCARD setup, etc.
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bluescreenoftom
Posts: 7
Joined: Fri Sep 09, 2011 2:52 pm

Wildly fluctuating Symbol Quality on some channels

Post by bluescreenoftom » Tue Feb 18, 2020 5:37 pm

My HDHomerun PRIME (hooked up with a Comcast Cablecard) is working excellent for the vast majority of channels, but for a select few, things are occasionally (not always) very choppy. When it's happening and I look at the tuner status, I notice that the Signal Strength and Quality are both usually very good (Strength is usually around 95%, quality is usually 100%) but the "Symbol Quality" fluctuates wildly between 5% and 100%.

I did some searching on the forums and the best I can tell is that it's probably some kind of signal interference. I do have the Prime sitting very close to my Wifi router... could that have something to do with it? Any other suggestions for remediating this?

jasonl
Posts: 15171
Joined: Sun Oct 28, 2007 9:23 pm

Re: Wildly fluctuating Symbol Quality on some channels

Post by jasonl » Tue Feb 18, 2020 7:42 pm

Being too close could cause that. Moving it further away (2-3 feet) would help.

bluescreenoftom
Posts: 7
Joined: Fri Sep 09, 2011 2:52 pm

Re: Wildly fluctuating Symbol Quality on some channels

Post by bluescreenoftom » Thu Feb 20, 2020 4:03 pm

Thanks. Just moved the device about 3ft away from the router. Will check back in if the issue persists.

bluescreenoftom
Posts: 7
Joined: Fri Sep 09, 2011 2:52 pm

Re: Wildly fluctuating Symbol Quality on some channels

Post by bluescreenoftom » Mon Feb 24, 2020 8:04 pm

Update: sadly it's still happening, currently on EVERY channel. My Comcast STBs seem fine so I highly doubt it's a signal issue.

Other suggestions?

jasonl
Posts: 15171
Joined: Sun Oct 28, 2007 9:23 pm

Re: Wildly fluctuating Symbol Quality on some channels

Post by jasonl » Mon Feb 24, 2020 8:11 pm

Enable the sending of diagnostic data on the HDHomeRun and run a channel scan (https://info.hdhomerun.com/info/trouble ... iagnostics) then watch live TV on something for 10 minutes and reply back with the device ID for your HDHomeRun and we will check the logs.

bluescreenoftom
Posts: 7
Joined: Fri Sep 09, 2011 2:52 pm

Re: Wildly fluctuating Symbol Quality on some channels

Post by bluescreenoftom » Thu Feb 27, 2020 7:19 pm

Device ID: 131024A0
Tuned in around 9:09 PM Eastern Time, 2/27. Was experiencing the issue noticably on FXXHD, the channel I tuned to at that time. Other channels seemed to work fine.

As a side note, prior to this, I tried replacing the cable coming from the wall to the HDHR. This seemed to increase the Signal Strength from 95% to 97% but I'm still seeing this particular issue on certain channels at certain times.

Edit:
I scanned around a little bit and found two more channels that also exhibit this issue:
FXX 63 MHz
A&E 67 MHz
HLN 69 MHz

I notice all the channels with this problem seem clustered together (MHz wize, not channel number) so it seems very very likely to me that this is an interference issue. Can you recommend a ferrite choke or special type of coax cable I could/should use to minimize this? Also interested to hear the results from the logs.

jasonl
Posts: 15171
Joined: Sun Oct 28, 2007 9:23 pm

Re: Wildly fluctuating Symbol Quality on some channels

Post by jasonl » Thu Feb 27, 2020 7:41 pm

Unplug the coax cable from your cable modem and see if it clears up. If so, you may need to add a 54MHz high pass filter to the line that goes to the HDHomeRun.

bluescreenoftom
Posts: 7
Joined: Fri Sep 09, 2011 2:52 pm

Re: Wildly fluctuating Symbol Quality on some channels

Post by bluescreenoftom » Wed Mar 04, 2020 7:03 pm

You called it, @jasonl. It was the cable modem introducing noise into the line. It was easy to confirm -- when I had no internet activity going on, the picture on FXX was fine. Then I went to Speedtest.net on one of my PCs, started a Speedtest, and boom - the picture went garbled.

I should next note how I had everything plugged in: Coax Jack in wall > coax cable > two-way splitter > one line to HDHR, the other line to the cable modem. To attempt to fix, I first purchased the 54MHz high pass filter you suggested and plugged it in after the splitter but before the HDHR. That helped a little but did not completely fix the problem. Fortunately, I had another coax wall jack nearby (plugged directly from the wall into a Comcast set-top box). I plugged the splitter and HDHR into this jack instead of the one with the cable modem, and the problem went away completely.

So there you have it. Just closing the loop in case anyone else ever runs into this issue. Apparently cable modems can be noisy on the coax line. Who knew.

Thanks again for the awesome support. You guys rock.

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