Copyright © Karl Dahlke, 2023
Pink Floyd says there are “13 channels of shit on the tv.” But why 13? 13 could have been a random number, or a large number of channels for its day, or a prime number, we don't know. I also don't know the tv broadcast system in England in 1980. But I do know the system here. The tv had a channel knob, and it went up to channel 13.
Everything was knobs and buttons then, mechanical knobs that you turned with a click, and buttons that you pushed in and out with a click. The top knob on our giant color tv set was a dial that selected the station, 2 to 13, and where there might have been 1, it said UHF. (ultra high frequency) That's how we got the higher channels. So if it was like that in England, he might have looked at the knob, UHF through 13, and simply said, 13 channels of shit on the tv.
Rewind to 1907, when the first practical vacuum tube was used to amplify electrical signals. Until then, electronics as we know it was not possible. It looks like a small capsule that you might swallow. Maybe a Contac pill. It's made of thin glass. Small is relative of course. It is a billion times larger than a modern transistor, drawing a billion times the current, and generating a billion times the waste heat, to perform the same function. That's billion with a b. I'll get to the transistor later. But in the 1910's we have the vacuum tube, and we can start to build radios.
The tube has a tiny electron gun in it, metal that gets hot and radiates electrons to the other end of the tube, and a voltage across the tube that changes the flow of those electrons. Air would get in the way, thus it is a vacuum inside. This was a descendant of the light bulb, another glass shape with no air inside. In fact Edison had some patents regarding the vacuum tube, but they were not practical in the 1880's. In science, one thing begets another begets another.
The vacuum tube can't work unless the anode is hot and radiates electrons. Heat is required for the functionality - no way around it. So they were never terribly efficient, but in 1912, they didn't have to be.
Because the tubes generated heat, they would drain a battery fast. Portable radios were not practical. The big deal in the 1950's was the transistor radio. People would say it almost as one word - transistor-radio. It could run on batteries, and you could take it to a picnic, or camping, or wherever. You could hear all your shows, and the news, and the weather.
So here I am growing up in the late 60's, and televisions were still vacuum tubes. Radios might be transistor, so they could run on batteries and you could carry them around, but telelvisions were giant things, they were never going to be portable anyways, so who cares. The picture element was a cathode ray tube, and it had to be as big as a microwave oven, couldn't really be much smaller.
We had a small black&white set in the den. My Dad couldn't afford anything else. My eyes were not good enough to resolve black&white. It looked like flickering shadows. I couldn't make out any images. I just looked down at my lego and ignored the tv. Then one day, glory be, Dad won a big color tv in some kind of raffle. In it came, big as life. It went into the den, and Eric got the small black&white set in his bedroom, lucky duck. I was amazed - For the first time my eyes were opened onto a new world. With the bright colors, I could see the pictures, the images, the people, the action. Still, I had to have my face right up against the screen. That did not go over well with my family. I learned to sit next to the tv, just off to the side, looking at the screen from the side, and still I could see most of the images, especially cartoons, which had exaggerated colors. Sometimes my head would wander closer, around to the front of the screen, and then Eric's voice would ring out. “Move your fat head!”
Let's talk about frequency. Starting in the 1910's, radio used amplitude modulation, with carrier waves from 0.75 to 1.6 megahertz, as described in the previous chapter. That is to say, the electrons in the antena at the radio station vibrated up and down between 0.75 and 1.6 million times a second, and the strength of this signal varied a few hundred times a second with the speech or the singer. It's the same today. Exactly the same system, though the transmitter and receiver are more efficient.
FM radio uses frequencies from 88 to 108 megahertz. Obviously these are higher frequencies than the AM band. In both AM and FM, the radio station identifies its frequency along with its call letters. That is an FCC law. WOMC 104.3, transmitting on 104.3 megahertz. Have you noticed that every FM station ends with an odd number? 104.3 ends in 3. This is separation. Stations will always be at least 0.2 megahertz apart. So you'll never hear a station with a frequency of 106.2.
tv uses higher frequencies still, in fact the band is called VHF or very high frequency. Well it was very high then, it doesn't seem that high now. Instead of using the hundreds of megahertz numbers, they just started assigning numbers 2 through 13. Somewhere somebody knows that channel 4 is 473.7 megahertz, etc.
Somebody decided that 13 channels of shit on the tv wasn't enough, so they made another band, called ultra high frequency, or UHF. This was so high it required a different antena. We had two antenas on our tv set, and on our roof, for VHF and UHF. It was combined into one unit, a straight antena for VHF and a circle antena for UHF. Someone who knows a lot more than I do about E&M knows why one antena works better for VHF and one for UHF.
UHF was channels 20 through 70. That top knob, 2 through 13, if I clicked it over to 1, it said UHF, and then there was another knob below for the UHF stations. It had lots of little clicks, so I could click around from 20 to 70. 56 was PBS, and 50 had all the kid shows that we liked to watch after school. On a good day we could get channel 62.
So what about the subject of this chapter, warming up the set? Remember that vacuum tubes have to get hot to work. When you first turned on the television, it could take 30 seconds for those tubes to warm up. You were literally warming up the set. Until the tubes were warm, there was no sound, no picture. You just waited.
If you looked close, just as the tubes reached operational temperature, a tiny picture appeared in the center of the screen. It was the tv show you were tuned to, but only a fraction of an inch across. The rest of the screen was still dark. In a flash, the picture expanded to fill the whole screen. You had to look carefully to see it. And when you turned off the tv, sometimes you could see the picture shrink to the center of the screen, then disappear.
One day the colors were all wrong. It looked like something from another planet. There were tiny knobs to adjust the overall brightness of the colors, but it looked awful no matter what adjustments we made. We called a repair man, who came to the house. You didn't lug these sets around in those days. He opened the back, I can remember watching him work. “Your red tube is broken.” he announced. He meant the tube that managed the red color on the set. The tv signal has separate signals for red green and blue, just like we have red green and blue dots on our computer screens today. These correspond to the red green and blue cones in our eyes - the colors we can see. Without red the colors were all wrong. When he said broken he didn't mean physically, the glass case was still intact. The electron gun inside was broken. He has all the spare parts he might need, so he replaced the red tube and left, after we paid him of course, and the colors were right again.
One day there was a problem with the vertical hold. The picture scrolled up and off the screen even as the same picture scrolled up from the bottom. If you could freeze frame it you might see the bottom of the picture on the top of the screen and the top of the picture at the bottom of the screen, and a big black line separating. But it just kept scrolling, sometimes slowly, sometimes at a dizzying pace.
A tv signal sends out a sync marker to say, this is the top of the picture. The electron gun goes to the top of the screen when it gets this marker. Then it starts painting across the screen, line by line, as directed by the signal from the tv station, then at the bottom of the screen it is done, and another sync marker, and back to the top of the screen for another picture. This happens 30 times a second, so fast it looks like continuous motion. There are also markers for end of line: sweep back to the left and paint the next line. If a tv gets out of sync, and isn't lining up with those markers, the picture can be off. This is what I was seeing. Our tv was painting the picture starting at the middle of the screen, or wherever. If the drift between our tv and the sync markers was slow, the scrolling would be slow. the picture slowly rode up the screen, to be replaced with the same picture below. But sometimes the tv was way off and the pictures would race by.
There was a vertical hold knob on the set to try to fix this. I don't remember if my Dad was able to fix it by adjusting this knob, or if we had to once again call in the repair man.
There you have it, state-of-the-art tube television in 1969.