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You could do a reasonable simulation of 441i using a DTV converter box set to letterbox mode, and a TV set, and assuming that there's enough oomph in the vertical jack up the height to make the black bars at top and bottom disappear to vertically fill the screen with picture, and increase the horizontal width to make the picture look reasonably correct.
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I thought about this and you have to be careful here. Picture resolution is dependent on a number of factors.
An important factor which is being overlooked is the Kell Factor. Kell attempted to define the required channel bandwidth (affecting horizontal resolution) against the number of lines. He asserted that because of the gaps between the lines, vertical resolution is lost which means that the horizontal resolution hence video channel bandwidth can be reduced. The Kell factor is the ratio or vertical resolution against horizontal resolution and its maximum value is unity or "1".
When vestigial sideband transmission was introduced for 441 television in the late '30's, the same 6 MHz channel containing the same 4.2 MHz video channel was used for the later 525 line system. The only thing that changed was the reduction of the Kell Factor to about 0.6. This means that the horizontal resolution of 525 video was less than 441 line video to compensate for the increase in the number of lines. Even in those days, it was felt that artificial picture "sharpness" could help compensate for the loss of resolution with the switch from 441 to 525. And the the horizontal resolution of 525 was further reduced with the introduction of color. The Kell factor with color broadcasts on US sets made after 1953, color and monochrome was now less tthan 0.5. However 405 line had a Kell factor of unity hence had considerably higher than expected horizontal resolution.
This may explain why when CBS engineers went to England in the late 50's and examined 405 line pictures first hand, they exclaimed that in many instances the 405 line pictures looked sharper than 525 line pictures.