[opendtv] Re: Channel Master Digital STB question
- From: dan.grimes@xxxxxxxx
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 9 Sep 2010 13:18:22 -0700
From Cliff Benham:
"I'm currently using a Channel Master model CM-7000 STB
for LO-VHF digital reception because it seems to be the one least
susceptible to signal loss out of 6 different Mfgr's boxes.
"The output of this STB feeds the TiVo so I can watch at my convenience.
"There is one nagging problem:
About twice a month when I start the TiVo expecting the morning news,
I'm met with a black screen with one of two different messages:
1. Encrypted program
2. No program
"Apparently there is a loss of signal which confuses the box and it hangs
until I intervene with the remote control.
If I turn the box off with the remote, wait 10 seconds and then turn it
back on, the program from the correct 'channel' comes back in and all is
well for several weeks or so until the same problem occurs again,
exactly the same way with the same results."
Cliff:
I have the same problem with my Channel Master CM-7000. I did quite a bit
of troubleshooting on the problem.
First, there was only one channel that seemed to have a consistent problem
and it was in the upper UHF. I looked at the boxes' signal level for that
channel and it showed 100 percent most of the time but would drop to 85%
every 10 or so seconds. All other channels showed 100% all the time. So I
thought it might be an RF signal issue for that channel. I varied the RF
levels into the box but it didn't change much, just the overall percentage.
So I hooked up a modern spectrum analyzer and monitored the signal. It
seemed to be perfect: nice flat level (equivalent levels of each VSB), no
fluctuations with time, apparently no reflections, high SNR, extremely
small bit rate error, etc. So I have to think that it was not the RF
signal that was the problem.
I sent the broadcaster and email but never received a response. However,
before I could throw some ATSC transport streams into an analyzer, the
problem went away. Now it still happens once in a while with that channel
but not very often. I believe the broadcaster changed something.
Meanwhile, my Philips DVR did fine with all the channels including the
troubled one.
One other thing of interest to me is that the Philips DVR does not look at
the program guide while the CM-7000 does provide this service. And the
channel that has the problem does not provide data in the program guide.
So perhaps those bits in the data stream are creating havoc for the
CM-7000.
My conclusion is that it has to be something in the ATSC transport stream
that the CM-7000 does not like. And there must have originally been a
wrong setting in their ATSC multiplexer/encoder that was causing the
problem. But how this affects the signal quality indicator on the CM-7000
I don't know.
Does any of this correlate with your problem?
Dan
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