Fine Tuners - What Was That All About

[Markxxx]

I remember seeing them as a kid on TVs that had dials, but I never had call to use it. I can't remember was it for both UHF and VHF or just one. I know in 1980 we got our first color TV that had no dials and of course no fine tuner.

Anyone want to fill me in about this? I am assuming some stations in some areas didn't come in well so you had to turn the fine tuner dial a bit?

 

[CTListener]

Just a guess, as I don't remember seeing that specific term used for a TV feature, but maybe it was an auxiliary knob or dial used to focus in on a UHF station. Older UHF-capable TVs ('60s and early '70s) didn't have the clicking channel selectors for UHF, just a rotatable dial with channel positions marked on it, and continuous tuning. Multiband radios sometimes had a "fine tuning" knob that would help when trying to separate amateur radio or utility signals on crowded shortwave bands. Maybe what you remember is the same sort of thing, adapted for TV.

 

[Weiserguy]

I remember those old TV's from my childhood apartment and my grandparents' homes. There was a coarse tuning knob to get you to approximately the channel you were trying to tune in on UHF (the VHF channels had those loud click-detent tuner dials), and then a fine tune knob that made it easier to zero in on the exact frequency of the station.

For example only, say the coarse knob moved the dial up (or down) 6 megahertz for each quarter turn, and then once you were in the desired target range the fine tuning knob moved up (or down) by 1 mhz for each full turn, so you had more precision in reaching the exact spot on the spectrum. It's sort of like using an old-fashioned analog radio dial, like on the GE Superradios, to get the exact zero spot for a station you wanted to acquire. Only the Superradio lacks that secondary fine tuning dial that the TV's (and some of the really old console radios of the 30's and 40's) did.

You should also keep in mind that circuitry wasn't as frequency-stable back then, there was no Auto Frequency Control circuit built in, and keeping that exact location on the dial often required repeated fussing as the channels drifted. The fine tune allowed the viewer/listener to readjust the TV tuner back to the exact station centerpoint after reception had started deteriorating.

 

[KeithE4]

The older VHF tuners also had a fine tuning knob concentric with the click-tuner. Some of those tuners weren't exactly stable, either, and that control was necessary. I remember one older set we had where the fine tuning could tune +/- one channel. A bit too excessive, but that's how they built them.

 

[Markxxx]

If I recall correctly both UHF tuners that were dial tuners (like radio) and click tuners (like regular VHF tuners) had fine tuners.

I remember them but I don't recall every using one or needing to use one. Just like the horizontal and vertical controls in the back of TVs. We'd play with them as kids but I never needed to use one.

Thanks for the info

 

[CTListener]

Just like the horizontal and vertical controls in the back of TVs. We'd play with them as kids but I never needed to use one.

The black and white, early '60s TV I watched at home as a kid required frequent twiddling of that vertical hold shaft. The picture "flipping" was a frequent problem. I always figured it had something to do with the vacuum tubes, as the tube radio I used for SWLing had a drifting problem, and sure enough it disappeared as a problem on solid state sets.

 

[Mark Roberts]

UHF tuners with detents weren't common until the 1970s. UHF converters tended to be continuous-tuning models. We got one, made by Channel Master, in 1971 when my hometown market finally became a three-station market with the third station being an ABC affiliate on UHF.

VHF tuners required fine-tuning controls due to positive and negative offsets, which altered slightly the center of the channel. I believe this was done to reduce co-channel and adjacent channel interference. This isn't an issue with digital broadcasting.

I bought a Zenith TV set in 1976 with detents on both VHF and UHF tuners. It had the most sensitive UHF tuner I ever had, and was a big step up from that converter-based set-up.

 

[KeithE4]

VHF tuners required fine-tuning controls due to positive and negative offsets, which altered slightly the center of the channel. I believe this was done to reduce co-channel and adjacent channel interference. This isn't an issue with digital broadcasting.

As I said earlier, the VHF fine tuning controls worked way past the +/- 10 kHz of the channel offsets. At least the ones my family had were good for +/- 6 MHz (aka, one channel either way).

I bought a Zenith TV set in 1976 with detents on both VHF and UHF tuners. It had the most sensitive UHF tuner I ever had, and was a big step up from that converter-based set-up.

The big problem with the old "radio tuning" UHF tuners were that they were designed to be as cheap as possible: A diode mixer and one transistor for the local oscillator. They were one notch above useless, even with a high-gain UHF yagi connected.

 

[TexasTom]

The purpose of the fine tuning control on older TVs was to compensate for the fact that at higher frequencies, electronics circuits tended to drift a lot. And if you go back to the fifties and sixties, even the VHF TV frequencies (54 MHz to 216 MHz) were high frequencies where the circuits were subject to drifting -- at UHF TV frequencies (470 MHz to 890 MHz), the drift was even worse.

So the fine tuning control let you compensate for drift in the tuner section of your television. As time went by, electronics improved and drift was less of a problem. When we eventually got to the direct access tuning (where you just type in the channel number), the problem essentially went away since the tuner frequencies were tied to a crystal reference and were rock stable. And so the need for fine tuning went away.

 

[Markxxx]

Thanks Texas Tom, now, is that what happened to the horizontal and vertical hold as well?

 

[TexasTom]

Thanks Texas Tom, now, is that what happened to the horizontal and vertical hold as well?

As I recall, the horizontal hold knob disappeared first, then vertical hold followed a number of years later. And I'm sure that it was again a case of improving technology and more stable circuitry. I remember that the 1970 Heathkit color TV my dad built would periodically lose horizontal hold and we'd need to adjust that particular knob, whereas I don't recall the subsequent TVs that we bought circa 1977/8 (from Toshiba, Panasonic, and Sony) ever losing horizontal hold. But even then, I do remember that those sets could lose vertical hold (the picture rolls vertically) and I remember needing to adjust the vertical hold occasionally well into the 1980s. By the time I bought an HD-ready set in 2001, both controls were gone and they weren't needed for any normal programming material.

As an aside, one benefit of having a vertical hold adjustment was the ability to get a picture from a non-NTSC signal. When I was in grade school, I had a small B&W portable Panasonic TV, and when we ended up in West Germany for a couple years in the early seventies, I was able to adjust the vertical hold to get a stable picture on the local PAL broadcasts. It was of limited use, though, since I still couldn't get sound from those broadcasts.

 

[landtuna]

As an aside, one benefit of having a vertical hold adjustment was the ability to get a picture from a non-NTSC signal. When I was in grade school, I had a small B&W portable Panasonic TV, and when we ended up in West Germany for a couple years in the early seventies, I was able to adjust the vertical hold to get a stable picture on the local PAL broadcasts. It was of limited use, though, since I still couldn't get sound from those broadcasts.

UHF was, for a time, a semi-good way to break into an early scrambled TV signal.

 

[KeithE4]

UHF was, for a time, a semi-good way to break into an early scrambled TV signal.

A VCR with thumbwheel tuning was able to decode the picture (not the sound) of ON-TV and other channels that used the same inverted-sine-wave scrambling method. Just turn the AFC off, diddle with the thumbwheel until the picture decoded. In Chicago, SportsVision used the same system. It was easy to get the picture this way, and listen to the sound on the radio with no delay. A homemade decoder wasn't even necessary for anything other than TV sound.

 

[Weiserguy]

When I worked at Gillcable in San Jose, early-mid 80's, one of my colleagues told me that the scrambling on their Oak converter boxes could be hacked by positioning a flat blade screwdriver at a certain place on the wood case and whacking it through with a hammer. Undocumented feature.

 

[tvnut]

A VCR with thumbwheel tuning was able to decode the picture (not the sound) of ON-TV and other channels that used the same inverted-sine-wave scrambling method. Just turn the AFC off, diddle with the thumbwheel until the picture decoded. In Chicago, SportsVision used the same system. It was easy to get the picture this way, and listen to the sound on the radio with no delay. A homemade decoder wasn't even necessary for anything other than TV sound.

This worked, but the picture didn’t stay stable, at least not on hockey, with so much white in the picture. Still better than nothing and radio filled in the gap.

 

[KeithE4]

This worked, but the picture didn’t stay stable, at least not on hockey, with so much white in the picture. Still better than nothing and radio filled in the gap.

Not by much. Dollar Bill Wirtz still wouldn't put Blackhawks home games on TV in any form, while the Sox and Bulls still aired some games on WFLD.

 

[IM42A]

As I recall, the horizontal hold knob disappeared first, then vertical hold followed a number of years later. And I'm sure that it was again a case of improving technology and more stable circuitry. I remember that the 1970 Heathkit color TV my dad built would periodically lose horizontal hold and we'd need to adjust that particular knob, whereas I don't recall the subsequent TVs that we bought circa 1977/8 (from Toshiba, Panasonic, and Sony) ever losing horizontal hold. But even then, I do remember that those sets could lose vertical hold (the picture rolls vertically) and I remember needing to adjust the vertical hold occasionally well into the 1980s. By the time I bought an HD-ready set in 2001, both controls were gone and they weren't needed for any normal programming material.

As an aside, one benefit of having a vertical hold adjustment was the ability to get a picture from a non-NTSC signal. When I was in grade school, I had a small B&W portable Panasonic TV, and when we ended up in West Germany for a couple years in the early seventies, I was able to adjust the vertical hold to get a stable picture on the local PAL broadcasts. It was of limited use, though, since I still couldn't get sound from those broadcasts.

Yes, agreed, that would be of pretty limited use indeed. Also, didn't it chop off part of the picture, in that NTSC is 525 lines and PAL is 625 lines?

 

[kevtronics]

Most vintage TVs pick off the audio signal from the same tuner used for the video, rather than having separate tuner circuitry for audio and video (which some TVs back in the '40s and early '50s did). As a result, especially as the TV's components drift with heat and age, it wasn't uncommon to have one tuning position that would give you a perfect picture but buzzy sound, and another position that would give you great sound but a snowy picture. A fine tuning control would let you find the best compromise between picture and sound.

 

[kevtronics]

Yes, agreed, that would be of pretty limited use indeed. Also, didn't it chop off part of the picture, in that NTSC is 525 lines and PAL is 625 lines?

No, because PAL has a refresh rate of only 50 Hz, versus NTSC's 60 Hz (well, 59.94 to be exact). So the electron beam is doing more sweeps across the picture tube, but more slowly, making the scan lines closer together.

 

[Negin]

The older VHF tuners also had a fine tuning knob concentric with the click-tuner. Some of those tuners weren't exactly stable, either, and that control was necessary. I remember one older set we had where the fine tuning could tune +/- one channel. A bit too excessive, but that's how they built them.

I remember those. We used to use that fine tuning knob to "fill" in the blank stations. Example you could fine-tune channel 3 so you could have either 2 or 4 on it. Results not seeing snow on the blank slots. Later on we restored 3 to normal when first got cable TV.