Talk:RF modulator

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Why can't 3 and 4 work together?

I have always wondered why if you try and use two RF modulators to encode channels 3 and 4 onto the same cable, they interfere with each other despite being discrete. Is it because the RF modulators are poor quality and they don't care about splattering channels for consumer grade devices since they figure only 1 channel will be used? Or is there some other reasonable technical explanation? Reswobslc 02:39, 8 November 2006 (UTC)[reply]

The RF modulator produces a tremendous amount of power next to the amount a tv would receive from an antenna, thus it overpowers the tv tuner on all channels. It is like walking into the bright sun from a dark room. Grock2 23:32, 18 December 2006 (UTC)

The tv channels needs to have a certain space between them in order to prevent them leaking into each other, it is a common issue that also exists in things like wireless networking --213.66.131.204 19:52, 19 April 2007 (UTC)[reply]

Yes, but isn't that built into the TV channel frequency allocation scheme? — Gwalla | Talk 20:46, 20 September 2007 (UTC)[reply]

True, and RF modulators that do allow many channels together do exist, they're used for cable TV for example, but the ones used in consumer electronics need to output a very powerful signal to completely overcome the other signals being received by the television, either from the cable or from the antenna. Its sort of like having to scream to a friend next to you in a crowded gymnasium, you need to be very loud in order to overcome the ambient "signal". Hope that helps explain it. Grock2 17:06, 11 October 2007 (UTC) —Preceding unsigned comment added by Grock2 (talk • contribs)

Most likely the issue is that of vestigal sideband removal not being handled properly by the RF modulator. Normally, the amplitude modulation of a signal produces an RF carrier and two sets of frequencies at the output, an upper sideband carrying the signal information (just above the carrier frequency) and a lower sideband effectively duplicating the same information. This inefficient use of frequencies is tolerable for an AM radio, but in TV it would waste a lot of spectrum. TV stations therefore remove most of the duplicate lower-sideband information before the signal goes on-air. If a cheap RF modulator removes this extra out-of-band signal far less effectively, part of the lower-sideband information from channel 4 will interfere with channel 3. It's not simply a question of an RF modulator putting out a powerful signal - it's that an RF modulator output also has a very poorly-filtered signal that does not prevent lower sideband from the channel 4 signal from occupying part of channel 3's assigned bandwidth. Manufacturers could fix the problem, but that would slightly increase the cost of making RF modulators. --66.102.80.212 (talk) 22:12, 9 March 2009 (UTC)[reply]

Modulator

Sir i want to know about types of modulator . how it work & and what is the procedure to convert the AV signal into the RF. —Preceding unsigned comment added by 59.182.144.168 (talk) 11:34, 29 January 2009 (UTC)[reply]

using rf modulator can we convert ntsc signal to pal signal

sir , using rf modulator can we convert ntsc signal to pal signal ......................? —Preceding unsigned comment added by 122.174.72.219 (talk) 06:13, 15 May 2009 (UTC)[reply]

Such converters do exist, and they are sometimes called "RF modulators", although they are a specific type of modulator and also include other format conversion electronics. You will need to make sure that you get the correct type of modulator for your conversion. Nimur (talk) 02:18, 17 May 2009 (UTC)[reply]

sata information

The "Design" section of this article states, "In order to display sata information..." What is "sata information"? Encyclopedia Blipvertica (talk) 13:30, 15 August 2011 (UTC)[reply]

BLAR

I blanked-and-redirected RF unit here. Brycehughes (talk) 07:02, 10 May 2014 (UTC)[reply]

Suggest merge October 2018

Channel 3/4 output discusses substantially the same topic as this article. Anything unique from that article could usefully be merged here. --Wtshymanski (talk) 21:19, 23 October 2018 (UTC)[reply]

vestigial sideband filtering

The article suggests that most don't do VSB filtering. The lower sideband of channel 4 would then overlap channel 3, which I would suspect could be enough of a problem to require the filter. Though mostly it depends on what the FCC says. The LM1889^[1] in one suggested use has a block labeled Vestigial Sideband Filter, but I don't see an indication of where to find one. If they were easily available, I would expect them to be used. Gah4 (talk) 20:05, 10 June 2019 (UTC)[reply]

References

^ "LM1889 TV Video Modulator" (PDF). rbsfm.org. National Semiconductor. Retrieved 10 June 2019.

[LM1889-1] "LM1889 TV Video Modulator" (PDF). rbsfm.org. National Semiconductor. Retrieved 10 June 2019.

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