We have a couple of old video cassette recorders that
still work just fine so we use them for time shifting until the
day that either a talking DVR comes out or I happen to get my
hands on a system good enough to install a video tuner card on
and run Linux as a DVR.
Our cable system still feeds several analog channels
down the line which are analog versions of the digital
transmissions of the local television stations as there is no
over-the-air analog TV any longer.
About August 1, we started noticing a raucous buzzing
sound on every single analog channel but 1, for some odd reason.
If you were monitoring through the VCr, the buzz was always
there and, of course any recordings made of the signal also
contained the buzz.
I recognized it as sync buzz, a problem that occurs
when the vertical sync pulse is too strong in relation to the
rest of the modulation envelope. Back in the analog TV days,
television stations actually got warnings from the FCC in the
United States and Industry Canada if spot checks showed the
vertical sync pulse out of spec, but cable systems are not
regulated in that manner so bad analog signals are a lot more
common than they used to be.
Anyway, I called our local cable provider to complain
and a technician came to our house. Fortunately, he appears to
be customer-oriented and observed the problem. He was even nice
enough to listen to my theory about the vertical sync, but I
could tell he was skeptical at first. I had said that I thought the
problem is at the head end and is system-wide. He said that they
would be getting calls from everywhere if that was so.
The thing about sync buzz is that different analog
television sets are not equally sensitive to it. Our Sony flat
screen can receive both analog and digital signals and had no
trouble at all. The two VCR's are made by Zenith and both
exhibited the buzz.
By the time he left, the technician thought I might be
on to something and said he'd check in to it. I was not holding
my breath.
This afternoon, he called us back and asked me to see if
the problems were still there. I checked and they were totally
cleared up.
He said that they did, in fact, discover an issue at the
front end and several more customers had called in today to
complain. They didn't have VCR's, but apparently did have TV's
that had the same problems with the signals. This is also called
AGC buzz and I won't bore you with the details of how it
happens, but that's sure one thing you will never see in digital
TV.
Anyway, the technician thanked me for helping them solve
a problem and essentially said I was right. How often does that
happen?
Martin
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