[mythtv-users] reception problem on just one channel

Joseph Fry joe at thefrys.com
Tue Jan 11 02:47:29 UTC 2011


> Mary Strimel <mary.strimel at gmail.com> says:
> > I have great HD OTA reception on all my local channels here in
> > Washington, D.C. but the CBS affiliate, WUSA-HD, does not record
> > correctly even though it reports 100% signal strength. The channel
> > behaves as if it has poor reception ... unwatchable stuttering and
> > blockiness ... but I have a feeling that it may be some other issue.
> > I am using an HD Homerun.
>
> The HDHomeRun's single strength indicator is more or less meaningless
> in and of itself; see
> <URL:http://www.gossamer-threads.com/lists/mythtv/users/308176#308176>.
>

As mentioned signal strength is a worthless measure by itself.  I could
create a white noise generator that plugs in to any antenna feed and
guarantees 200% signal strength on any channel (hmm new product to sell to
suckers).  Of course that signal would be strong but worthless (but
profitable?).  Most likely you will find low signal quality if you fire up
"HDHomeRun Config GUI" and tune to that channel.

The most common cause for issues like this in your area is probably the
unnecessary use of an amplifier or amplified antenna of some sort, or just a
bad amplifier/amplified antenna.  All amplifiers will amplify noise and
cause noise themselves (much like the noise generator above).  While great
for overcoming cable loss when you have a long cable run, the noise they
generate will often turn a noisy-but-usable signal into complete crap.  So
essentially, all of those amplified indoor antennas are usually a waste of
money; a good amplified antenna should put out a higher QUALITY signal than
an amplified one.

Another common cause are multipath signals, where your antenna is picking up
the same signal from a second reflective source.  The early HDHRs had
horrible multipath rejection (but I still love mine).   This source can be
most anything reflective at that channel frequency.  Try adjusting your
antenna, or switching to a more directional antenna (which will not receive
the reflected signal so strongly if it comes from a different direction)

Check tvfool and report the details about the channel you are trying to
receive; channel,  distance, path (los, 1 or 2 edge), nm (noise margin), and
power.  And let me know more about your TV setup (antenna, amplifiers, and
splitters).

Probably best respond directly rather than to the list, this is way off
topic.
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