March 1963 Radio-Electronics
[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Electronics,
published 1930-1988. All copyrights hereby acknowledged.
Your search is finally
over. That "TV Frequency & Marker Chart" you've been having such a hard time
finding is right here in black and white. That's right, now while you are tuning
that VHF / UHF television for the best possible reception of both audio and
video, simply cross reference the channel number with the corresponding audio
carrier and video carrier frequencies and you're good to go. Be sure to have
your test probe at the proper "looker point" in the circuit, or you might be
tuning for the wrong waveform. Thank Radio−Electronics magazine for the
favor. Of course I'm kidding; almost nobody needs this kind of information
anymore. But, there are still a few hobbyists who restore and service those old
sets. By the way, I don't ever recall hearing of the term "looker point" when
referring to a test point. You?
TV Frequency & Marker Chart
By Don Dudley
When making a quick check for TV tuner alignment, a list of channel frequencies
and their video and sound carriers will come in handy.
Each channel is 6 mc wide, and the video carrier in each is 1.25 mc above the
low limit. There is the standard 4.5 mc between video and sound carriers. This places
the sound carrier 0.25 mc below the high-frequency limit of the channel. The sweep
picture as seen at the looker point (rf test point) is shown in Fig. 1.
Those who doubt the accuracy of their markers can use the transmitted sound and
video carriers by using the hookup in Fig. 2. Use a resistance value that gives
a clear undistorted marker.
Fig. 1 - The waveform at the TV tuner looker point.
Fig. 2 - With this arrangement you can use TV station signals as markers.
Posted May 1, 2023