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First Intercarrier and Last Split-Sound
I was looking through Riders 1 recently and pretty well all the sets listed are split sound. That is, the sound take off point is before the second video detector. This means that fine tuning is critical and must be optimized for best sound quality. Note that the 4.5 MHz intercarrier audio IF of US, Canada and Japan TV's are present in intercarrier sets only.
The RCA 630TS sound take off point is immediately after the tuner. Starting wih I believe the RCA KCS28 chassis, the sound take off was after the second video IF stage. RCA kept with the split sound design up to about 1952 when pretty well everyone else had moved to the intercarrier design. Is anyone aware of any of any manufacturer brand sets of this or later vintage which remained split sound? The earliest intercarrier set I have seen I think may have been a 1947 or 1948 Belmont. Most of the GE's from about 1948 appear to be intercarrier. What is the earliest intercarrier set that you know of? Note that all TV's after the early fifties were intercarrier except for the UK and France. The UK 405 line and French 441, 819 and most recently 625 employ AM sound and hence are inherently split sound since they cannot use the intercarrier process. Incidently, the United States television listed on ebay right now I believe is split sound. Does anyone have details? |
#2
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I always thought it was Motorola that pioneered intercarrier sound with the introduction of the VT-71 in 1947.
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tvontheporch.com |
#3
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In 1982, I bought a high-end Sony Profeel separate monitor and tuner, and (way before I understood what the terms meant) the tuner (VTX-1000R) had a switch to select between intercarrier and split-carrier sound. I remember switching it to split carrier and being shocked that the background sound became nearly silent, with not even a bit of buzz.
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
#4
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Back when stereo audio for TV was developed, around 1984, RCA used, in addition to the regular video IF strip, a special video IF strip for the sound. One peak for the picture carrier, and another peak for the sound carrier. The "video" detector just beat these two carriers together to get the 4.5MHz sound IF, without incidental bandwidth tilt, which can cause that buzz, which will trash stereo decoding. There's no Nyquist slope at the picture carrier, like regular video IFs have.
That Sony with the choice of sound IFs sounds quite interesting. I suppose the tuner was a PLL based on a crystal to yield an accurate local oscillator frequency, so a split sound system would always work. They could have used the FM detector to provide some automatic frequency control correction (probably to induce a slight shift in frequency of the crystal reference oscillator, to shift the local oscillator as a result of the PLL). Oh, I see VK plants web page links and $ coins on words like "Sony". Well, if the money Sony and others pays for it helps keep VK on the air...
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#5
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I seem to recall reading that during WWII the US government developed intercarrier sound to reduce tube counnt and weight on special purpose TV equipment they were using, but I may be imagining some of the details.
Tom C. |
Audiokarma |
#6
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Somewhere I have a letter from George Fowler?? He was a GE engineer
in the pre war days then moved to Motorola. One of his accomplisments while at Motorola was the invention of inter-carrier sound. In the 50's he moved to Zenith. He had told me the first set to have the inter-carrier sound installed was his pre-war HM-225. I was hoping he still had that but all he had left at the time, early 1980's, was an a post war Motorola! |
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Quote:
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#8
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I wonder if Panasonic, Sanyo, Sharp or any other consumer manufacturer yields the "coin" similar to Sony? Last edited by Penthode; 05-29-2011 at 10:22 PM. |
#9
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That tuner was indeed PLL-based, with no fine-tuning controls available or needed. The newer version (VTX-1100R) did not have the split/inter switch, and I do not know which circuit it used. The '1100 tuned cable channels up to 125 versus the '1000 that only went to cable channel 36.
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
#10
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There was a separate IF amp and detector for the video signal, which did have the Nyquist slope. In 1984, that meant one extra chip and a SAW filter module.
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Audiokarma |
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