Cable Channel 1 (Not to be Confused With B'cast Channel 1)

> [TELECOM Digest Editor's Note: [...]
> I wish we got WB here in Independence. [...]
> channel 1 and 4 are not occupied at all [...]
> One and Four are not [...]

The "Channel 1" on your TV set (or converter box) probably won't ever
be occupied because it isn't at the same frequency as the long-defunct
Broadcast Channel 1 recently discussed here on TD. Cable Channel 1
fills the blank space between Channels 4 and 5. But because that
space is only 4 MHz wide (unless Independence has an extremely unusual
cable system), it can't be used for a TV channel anyway.

Here's the history as I understand it:

In the early days of the cable TV industry, only Channels 2-13 were
used. Just as in the over-the-air broadcast world, second-harmonic
distortion was a potential problem; however, the fact that Channels
2-13 were split into two separate octaves rendered this problem moot:
all second harmonics fell outside of the bands of interest.

But as the industry grew, more channel space was needed, so channels
14-22 were added in the midband (120-174 MHz). Once those were used,
more channels were added in the superband (above channel 13).

These new channels were vulnerable to, and created, all sorts of
distortion products that fall in other channels. These products are
classified as follows:

SECOND ORDER DISTORTION: F1 +/- F2 (including second
harmonics). Example: the sum of the channels 3 and 4
visual carriers:

61.25 + 67.25 = 128.5 MHz.

This combination produces a spurious signal at 128.5
MHz, which falls 1.25 MHz above the visual carrier of
cable channel 15, right in the middle to the video
sidebands, where it causes rolling horizontal lines in
the picture.

THIRD ORDER DISTORTION: F1 +/- F2 +/- F3 Example:
channels 7, 8 and 9 visual carriers:

175.25 + 181.25 - 187.25 = 169.25 MHz

This combination produces a distortion product at 169.25
MHz, approximately at the visual carrier frequency of
cable channel 22. But (assuming that the three carriers
are generated by independent oscillators), this product
will not fall precisely on the visual carrier, so it
produces a "thumbprint" in the desired picture. If the
oscillators drift, the thumbprint dances around.

These problems became particularly severe as amplifier cascades became
longer: the more amplifiers in a cascade, the worse the distortion at
the end of the line. (The design goal for most cascades was a maximum
of 20 amplifiers, but I once heard of a cable system in California
that had a 67-amp cascade!)

To solve (or at least hide) these problems, various schemes were
developed for locking the visual carrier frequencies together at the
headend. The goal was to force the distortion products caused by the
interaction of visual carriers to fall precisely on top of other
visual carriers, effectively masking them.

Two schemes were developed:

- INCREMENTALLY RELATED CARRIERS (IRC)
(not to be confused with Internet Relay Chat)

This scheme phaselocks all visual carriers to a master oscillator
operating at F0 = 6.0000 MHz according to the formula

F = F0 * N + 1.2625

where N is an integer and 1.2625 is a constant (it was originally
1.25, but it was offset to 1.2625 to avoid conflict with aeronautical
communications -- but that's a different story).

Thus:

Channel 2 visual falls at 55.2625 N = 9
Channel 3 visual falls at 61.2625 N = 10
Channel 4 visual falls at 67.2625 N = 11
Channel 5 visual falls at 79.2625 N = 13
Channel 6 visual falls at 85.2625 N = 14

This scheme solves the third-order distortion problem, although it
doesn't solve the second-order problem.

Note that this scheme moves Channels 5 and 6 up by 2 MHz.
Consequently, this scheme only works if special arrangements are made
to accommodate this shift. Some cable operators provided special IRC
converters; others just left 5 and 6 vacant. Some "cable-ready" TV
sets were equipped with obscure little switches (or menu options) that
made the shift.

The converter that PAT described here several years ago was apparently
able to receive Channels 5 and 6 at both standard and IRC frequencies.
It received standard 5 and 6 on positions labeled 5 and 6, but it
received IRC 5 and 6 on positions labeled something else (55 and 56 as
I recall). Because the standard channels overlap the IRC channels,
it's not possible to use both. And that's why PAT was told that he
couldn't use Channels 55 and 56 if he used Channels 5 and 6.

Note that this scheme leaves a 6-MHz gap (72-78 MHz) between Channels
4 and 5. Which just happens to equal one television channel. And
that's cable Channel 1, with a visual carrier at 73.2625 MHz.

- HARMONICALLY RELATED CARRIERS (HRC)
(not to be confused with Hillary Rodham Clinton)

This scheme phaselocks all visual carriers to a master oscillator
operating at F0 = 6.0003 MHz +/- 1 Hz (that's right: plus-or-minus ONE
HERTZ) according to the formula

F = F0 * N

where N is an integer. The master oscillator frequency was originally
6.0000, but it was offset to 6.0003 to avoid conflict with
aeronautical communications -- again, that's a different story.

Thus:

Channel 2 visual falls at 54.0027 N = 9
Channel 3 visual falls at 60.0030 N = 10
Channel 4 visual falls at 66.0033 N = 11
Channel 5 visual falls at 78.0039 N = 13
Channel 6 visual falls at 84.0042 N = 14

This scheme solves both the second order and the third-order
distortion problems.

Note that this scheme moves everything down by (about) 1.25 MHz,
except for Channels 5 and 6 which move up by 0.75 MHz. Like IRC, this
system only works if special arrangements are made to accommodate the
shift. Some cable operators provided special HRC converters, and some
cable-ready TV sets were equipped with switches or menu options.

This scheme also leaves a 6-MHz gap (approximately 70.75- 76.75 MHz)
between Channels 4 and 5. So again, we have cable Channel 1, this
time at 72.0036.

In recent years, the use of fiber optics in cable TV networks has
dramatically reduced the need for long amplifier cascades (some
networks now have cascades as short as two amplifiers). This in turn
has virtually eliminated the need for IRC and HRC frequency schemes.
So most cable TV systems now use the "standard" frequency allocation
scheme: cable channels 2-13 fall at the same frequencies as broadcast
channels 2-13. And "cable channel 1" has been relegated to the
dustbin of ancient history.

So, unless your cable system in Independence uses either IRC or HRC,
there is no cable Channel 1.

Neal McLain
nmc...@annsgarden.com

[TELECOM Digest Editor's Note: I think I said before that regards
broadcast over the air channels, all we can get so far out here from
nowhere is Channel 6 from Pittsburg, Kansas, and not very clearly.
Thus, when Time-Warner offered a little cable service several years
ago people jumped at it. The *original* cable was 22 channels, of
which 3 were CBS affiliates in KC, Joplin, MO and Tulsa, OK, 2 were
NBC affiliates, etc. In other words, the same program many times on
different cable channels, plus a channel each for municipal, the
high school and Independence Community College. The few left-overs
were TBN, two PBS affiliates (Topeka and Tulsa) and I think they had
the weather channel. The cost was eighteen dollars per month. Long
before any cable at all -- in the 1970's -- Indepedence had a very
low-power TV channel which all the time was focused on some weather
gauges somewhere, with classical music in the background. I think
that was some UHF broadcast channel.

Then Time-Warner added about 30 more channels, some of which were in
what was called 'extended basic' (the original was renamed 'basic')
and this 'extended basic' included things like AMC, Discovery, History
and similar. The price for those became $34.95 per month which
included the original 22 channels. In addition, a few new channels
were 'premium service' including HBO and Cinemax. Then they came along
last year and expanded the 'extended basic' to include at no extra
charge (above $34.95) channels like Disney, FX, Women's Entertainment,
Black Entertainment, both C-SPANS, etc. We are now up to 60 channels
in 'extended basic', with a couple dozen pay per view and/or premium
channels at additional cost, and radio musical background on a few
others. 'They' say they are going to add cable-modem service 'soon'.

Two weeks ago in the Independence Reporter a story said Time-Warner
was going to split -- leave town -- and that some other cable company
was taking over. I asked the woman in the office what was going to
become of them; she said that she and her husband (the technical and
field repair guy) were being hired by the new company. She told me
the company name which I have forgotten. The idea is apparently that
Time-Warner wants to get out of small, rural markets like this one,
and traded S.E. Kansas and another small market to some cable company
in exchange for taking over some large city TWC wanted. She asked me
again, 'do you wanna bring me that dish off your roof and turn it
in here so I can tell DISH to come and get it? I can give you a great
deal on some premium stuff, if you turn in the dish here in our
office. Three months free and no installation charges.'

The *old* original 'basic' apparently left the original broadcasters
in the same place on the dial where they were over the air when
possible. Cable 2 was b'cast 2 and CBS. Cable 11 was b'cast 11 and
PBS, etc. But imagine having the same show on cable 2, 8 and 9 all
the time because of them each being CBS, other than local news, etc.

On the radio, there are umpty-zillion AM stations of course,
especially at night when I can even get WGN from Chicago sometimes
and WHO from Des Des Moines and KMOX in St. Louis. But I do not listen
to AM radio. KOA in Denver comes in like gang-busters all the time
at night. The four local-area radio stations are KIND (1010 AM) and
KIND-FM (102.7 FM) both owned by Bill Curtis of A&E fame (he is a
native of Independence; they have his pictures all over at the radio
station, even though the FM side is mostly satellite from Los Angeles
and the Clear Channel Company), and KGGF (690 AM) and KGGF-FM both of
Coffeyville, owned by the Coffeyville Journal newspaper. I don't
listen to them either. I mostly listen to the public radio station
from the state university in Pittsburg, Kansas 89.9 FM which comes
in pretty well. Public Radio in Tulsa 88.9 does not come in very well
at all. Fortunatly my computers keep me busy. PAT]

That's common in areas with poor over-the-air reception, but in places
close to VHF stations it's common to put those stations on different
channels -- to avoid ghosting caused by those stations' strong signals
leaking into the cable -- and use their "normal" channels for
lesser-used stuff such as access channels. In Louisville, where we
have only two full-power VHF stations -- NBC on channel 3 and ABC on
11 -- the cable company puts them on channels 2 and 4 respectively and
uses 3 for The Weather Channel and 11 for C-SPAN. This isn't possible
in New York or Los Angeles, where there are seven local VHF stations
(and only five blank spots on the VHF dial), and impractical in places
like Chicago where so many channels would have to be left fallow, so
some viewers there have to use converters if their TV sets or VCRs are
inadequately shielded. (In fact the first cable converter, Oak
Industries' Focus-12 introduced in the late 1960s, only covered
channels 2-13 and was built specifically to fix the "ingress" problem
in Manhattan.)

Channel 1 exists on both cable systems here in Sacramento (SureWest
and AT&T). On SureWest it is a menu of optional features, on AT&T it
is Home Shopping Network.

Both systems require the use of the company's converter box to tune
channels except those in the Economy Basic range. (I've always
assumed that is because the rest are scrambled.) The EB range does
not include channel 1 but does include all of 2 through 13.

So wherever channel 1 is located, it is not 72-76 MHz unless they've
found some way of compressing a full cable channel into that range.
My guess is that it is the original 48-54 MHz channel. This should
not cause a conflict with anybody if the cable signal is prevented
from radiating over-the-air; and I'm sure it is, or thousands of
people would start getting "free rides" by putting up antennas.

Here's what I have seen over the years:

Columbia, Mo.: KOMU/8 placed on cable 7; cable 8 used for weather
radar for a long time, now blank; KRCG/13 on cable 12; cable 13 used
for municipal access. Ingress a MAJOR problem on 8; relatively minor
on 13 but the builders of the system took no chances and that's been
carried down through the successor companies.

Kansas City: WDAF/4 on cable 6; KCTV/5 on cable 3; KMBC/9 on cable
12. Kansas City has most of its TV towers in the center city area.
Ingress is a major problem and the Kansas City cable system was old
and creaking (couldn't go up past cable 37) until about 1997. Oddly
enough, then-KYFC/50 was shunted off to cable 9 where it suffered
interference from KMBC if you lived in the urban core (as I did, just
five miles from most of the sites). Cable 4 became a leased-access
channel. Cable 5 has been used for various things over the years.

Chicago: The TCI/AT&T system put WBBM/2 on cable 3 (cable 2 was blank)
but left the other channels alone. The quality of the system varied
tremendously. At my first Chicago location, ingress and ghosting were
a big problem on the other V's. Then I moved five blocks away to the
other side of Broadway. The quality suddenly became much better. I
suspect that, at my first location near Sheridan Road, there may have
been quite a bit of leakage due to theft of service. The 21st Century
(now RCN) system was brand-new, did not move any channels, and there
was no ingress or ghosting.

San Francisco: No changes. Likewise in Oakland, a problem for us
because we live at a location whose elevation is above the elevation
of the main antenna on Mt. Sutro. -- the house is as line-of-sight as
it can be! We can't use our cable upstairs -- I've tried several
strategies for shielding and and attentuating -- and none has
worked. This was true even after AT&T installed new lines with better
signal strength in our neighborhood. Yet downstairs there are no
problems. Either there's something in the house wiring or we have
enough natural shielding from the hillside to make it work there.

We do see some minor interference, I believe from UHF 26, on cable 71
(the Travel Channel, woohoo). I haven't compared the two sets of
frequency to see what the precise overlap is. There's something
similar on our cable 77 which is used as a preview channel for AT&T to
flog its digital-cable channels.

Of course, upstairs, rabbit ears are sufficient for the channels
transmitting from Sutro and San Bruno -- the two U's from San Bruno
hardly even need that.

Mark Roberts | "This is local television. Get off your high horse!"
Oakland, Cal.| -- Gary Radnich to Wendy Tokuda on KRON-TV's
NO HTML MAIL | 9 pm newscast (said in jest), August 9, 2002

[TELECOM Digest Editor's Note: Something weird about our cable here.
We get channels 2 through 62 (channel 4 is skipped) and from 63
upward, I get a blue (no signal) blank screen the rest of the way
up to channel 125 on my television. Except 'channel' (or position)
70 on the VCR/TV combo I have. Channel 70 was picked up in the auto-
tuning process and is still there with a *black* (in use) screen.
Something somewhere is leaking through a bit I guess. Channel 70
never has anything on it, just that dark and occasional flickering
screen. I was hoping that maybe fine tuning of the set would get me
some hint of programming there, but no go. I get two channels for
the inputs on the VCR, known as L-1 and L-2 should I wish to plug in
a video camera, etc. PAT]