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schroff

join:2003-08-28
San Antonio, TX

[TWC] 723-MHz interference?

I have three different computers with different PCI tuner cards (Ceton InfiniTV, Hauppauge 2250 & AverMedia 780) that all exhibit what I have seen described as macroblocking on the same channels at exactly the same points in time. The 8300HDC does not show this problem. The Samsung's internal tuner exhibits only a brief audio dropout at these points in the stream.

According to the Ceton diagnostics, the effected channels all use a base frequency of 723-MHz and I generally have a signal of +8dBmV with SNR of 36.2 dB.

In San Antonio, TX, the most effected channels are KENS 105 and KMYS 107. I have found other Ceton owners in both San Antonio and Austin discussing this same problems with their systems. Apparently this is not confined to the Ceton cards as there is evidence that other cablecard devices have this same issue in HDHR & TiVo devices as well.

All of this leads me to believe that there is some known susceptibility in that frequency range that is better filtered by the 8300HDC and other tuners than PC-connected devices. Is there any evidence of or further directions I may proceed in trying to resolve this issue?

I appreciate all input on the subject and thanks in advance.


File Quit
Mac Geek
Premium
join:2002-11-28
San Antonio, TX
I also am in San Antonio, and have a Hauppauge 1600 PCI tuner. The CBS ClearQAM channel (KENS if im not mistaken) is terrible! I receive the Macroblocking as well... but thought it was due to an older card. My SNR for the channel hovers between 30 - 33 dbm. The card does not give signal power levels, but my modem registers at 1 dBmV. I am located in 78257.

I have no idea how to proceed, but would be glad to assist in any troubleshooting efforts.

edit -

I should also note that this is not a cablecard tuner... i only have the analog cable through the bulk cable that timewarner negotiated with my apartment complex. i receive the OTA channels through ClearQAM.

--
Apple. Switch to Mac. »www.apple.com/getamac

schroff

join:2003-08-28
San Antonio, TX
reply to schroff
I am certain that I have reached the end of what may be accomplished, but what I have found is the higher the signal level I can provide (+18dBmV with >36dB SNR) to any of these tuners, the better those effected channels are BUT the signal is the too high for the tuning adapter to operate reliably. Adding attenuation to get get my low to high of mapped frequencies at +2.1 - +8.2dBmV, all greater than 36dB SNR is the most workable balance, but KENS is still often unwatchable through any PC tuner. I just do not see why internal screen tuners and TWC cable boxes are immune to this.

I have added a tilt compensator which reduced my low to high frequency level difference from 18dBmV to 8dBmV.

I have also added an 860mHZ Low-pass filter immediately in front of the tuner input. This seems to have lessened the occasional one-line screen disruption on other channels.

With all that TWC just sees the numbers and says I'm good.


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:17
The PCs could be generating a RF signal around 723 Mhz or some multiple (2.8 Ghz, 1.4 Ghz, 360 Mhz, etc.) of it that is interfering with the internal tuner...

schroff

join:2003-08-28
San Antonio, TX
That may not explain why this also seems to exist on ethernet or USB connected hardware.


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:17
723 Mhz should be limited to low power TV stations and translators. Got any of those around your neighborhood? FCC database searches don't bring up anything.

schroff

join:2003-08-28
San Antonio, TX
No, nothing near me and geographically, the others I have heard from in San Antonio are all over the place.

G0d

join:2012-11-29
reply to schroff
I might have skipped over it but have you tried just connecting up to a digital tv tuner directly from that outlet? See if you get the same picture quality. Does your ceton card diags show anything other than SNR for qam tuner quality? Your SNR might be good but you may have bit error counters that are high causing your issue.

schroff

join:2003-08-28
San Antonio, TX
Yes, the very first thing I did was connect the Ceton through the Cisco tuning adapter directly to my drop with nothing else connected. The rate of macroblocking occurrences was about the same. It varies widely from several times per minute to once in several minutes.

I am not seeing any errors through the Ceton diagnostics of the tuners, tuning adapter or cablecard.

magno101

join:2013-03-04
San Antonio, TX
reply to schroff
Howdy Schroff,

Just wanted to chime in here and say that I've got the same exact problem on my end as well. There's a long thread running at thegreenbutton »www.thegreenbutton.tv/forums/vie···8&t=3060 documenting a couple of us having the same issues.

Just wanted to chime in here as well to say that you're not the only one and that I hope we can get to the bottom of this.

G0d

join:2012-11-29
I notice you both are from San Antonio. Is the problem specific to people who are living there? I did a quick check for OTA frequencies in this range and this is what I found in that market. Looks like that spectrum OTA is in use for some LTE mobile tv. Just something to think about.

»assets.fiercemarkets.com/public/···fest.pdf

Expiration Date
06/13/2019
Market
BEA134 - San Antonio TX

Frequency Band (MHz)
722-728
Licensee FRN
0017173121
Radio Service
WY - 700 MHz Lower Band (Blocks A, B, E)
Licensee Details
Manifest Wireless L.L.C.
1110 Vermont Avenue, NW, Suite 750
Washington, DC 20005
Attn: Alison Minea
Phone:(202) 293-1216
Fax:(202) 293-0984
Email: Alison.Minea@dishnetwork.com
Contact Details
DISH Network L.L.C.
1110 Vermont Avenue, NW, Suite 750
Washington, DC 20005
Attn: Alison Minea
Phone:(202) 293-1216
Fax:(202) 293-0984
Email: Alison.Minea@dishnetwork.com

schroff

join:2003-08-28
San Antonio, TX
If our problems were attributable to an OTA signal, blocking the ingress of that signal would be a TWC problem. That brings up the point that we are seeing this in different areas served by different fiber to coax hubs. I would presume that feeds to TWC are not over coax and would be immune to such.

So, it is seeming less likely that interference is the cause and opens the possibility that the process of processing these stream feeds to QAM may be resulting in collisions, or exceeding the available bandwidth of that particular QAM channel's frequency.

Noting that there was a change from QAM-56 to QAM-256 for KENSDT, which consumes more bandwidth, some time ago, I suspect something else in play here. This is further supported by the problem of PC-connected clear QAM receivers even finding KENSDT through a scan and require it being manually added to a channel list by its major and minor frequencies.

Why this problem does not exist with most internal TV tuners and STB devices must have something to do with their differing sensitivity, filtering, or some processing TWC is not sharing properly with cablecard device manufacturers.

Since we are not seeing any error reporting during these events, the stream must be perceived as coherent by our receivers and passed on to the rendering processors.

Granted, much of this is my conjecture, but just what does it take to quantify it from here?