opposite of an RF Modulator?

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The opposite of a RF Modulator is a RF Demodulator. These take many forms depending on what you would like to recover from a modulated signal. A RF receiver is a form of a demodulator. It recovers the signal from the modulated RF signal and outputs it as whatever. Think AM and FM. These further come in types such as analog, digital, pulse and others. What detects this information is many faceted. The one that comes to mind is a simply diode detector that designed to a plethora of specifications is wide or narrow band, freauency sensitive and anything else you would like. I am sure Wikipedia has lots of discussion that would prove interesting to you.

Bob AZ

[snippety snip]

Some (many? most? all?) current generation U.S. flat-screen television receivers include both NTST (analog) and ATSC (digital) tuners. The NTSC tuners work the same way on the flat-screens as they do for the older, CRC-based models, so you may not need to make any changes to your distribution system at all.

Not easily or cheaply. The consumer-grade market for such a gizmo is very small. If you wanted to do the heavy lifting, the specs for each are available and it certainly could be done in principle. Some guy with a web page has probably already done it but you're not likely to find one on the shelf at WalMart.

--
Rich Webb     Norfolk, VA

it's called a tuner

I think this is a troll, but...

To make a long story short... Almost all TVs have inputs for analog audio and video. By that I mean "baseband" (not RF) signals, such as composite NTSC or component 1080p. With high-quality cabling, you should be able to run these signals to multiple sets.

I used to use a VCR as a tuner in my TV projection setup. Worked pretty well. I bet an old VCR with a busted tape transport can be had pretty cheaply these days.

"William Sommerwerck" wrote in news:ht3f3e$jpu$ snipped-for-privacy@news.eternal-september.org:

I don't know if those outputs are made to drive -multiple- sets. I believe they are only 1:1.

They still require impedance matching,too.

--
Jim Yanik
jyanik
at
localnet
dot com

Well, a RF *demodulator* takes analog RF and converts it to analog A/V. A A->D converter will convert that to digital.

A A->D converter will do the trick. $$ for video.

Question: For the digital TVs, why not just use the original digital signal?

On 5/20/2010 11:36 AM Jim Yanik spake thus:

Just curious: what *is* the impedance of such cables? I'm guessing it's not the 50 or 75 ohms of RF cabling.

--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

They have to be made to drive a 75 ohm load to work with a standard video input. If you can turn off the 75 ohm termination in all but the last monitor, you can drive multiple monitors. I used the tuner & power supply from a damaged VCR 20+ years ago as a secondary demodulator at the TV station I worked at. I looped it back into a spare input on the

3M video router so the director could see what our views saw, instead of our in hose video. That cost be $2, instead of over $3,000 for a commercial demodulator like the one we used at our transmitter site.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

I don't know. I guess I can. I didnt' think of it. Thanks.

I guess I would have to use a couple spitters to make a route around the RF modulator, and then I would be running analog and digital on the same co-ax, right?

Well that would be great. I'll keep my eyes open for that.

Okay.

Thanks to you and to Bob, AZ, David, William (even though he thinks I'm trolling!) Jim, David, Michael, and UCLAN.

There are some questions that -- to me, anyway -- have such obvious and simple answers, that it's easy to believe some posts are trolls.

Not easy, a quality real time MPEG coder takes a lot of computing power and the mass market does not request such device, so for now it is expensive. However I'm guessing you are thinking for the future when TVs are no longer equipped with analog tuners. At least a baseband video input is likely to be available in TVs for a long time so an easy option would be an external analog tuner. Yes, they exist and even have remote control just like digital tuners.

However chances are that MPEG coders and CODFM modulators become cheap enough for domestic use in the future or even DVDs, etc output a modulated digital RF signal just like old VCRs did with an analog RF channel. Yet I belive it is (and will be) cheaper to buy a DVD or other set top box for every TV than to distribute the signal from one.

If you split it off to the digital TVs *before* it goes into the D->A converter box, then it would be only digital - right?

Phrase your question properly and you will get better results.

Google 'ATSC Modulator'.

PlainBill

Probably unnecessary.

Almost all digital-cable TVs can receive and decode both ATSC (digital) and NTSC (analog broadcast/cable) signals. They can look at any proper 6 MHz slice of the broadcast spectrum, look at the signal in that range, determine whether it's NTSC or ATSC, and display it properly.

You can mix NTSC signals (e.g. the "channel 2/3" modulated output from a VCR or DVD player) with ATSC digital, as long as you don't try to put both on the same channel. The best way to do this is with a proper single-channel combiner.

You ought to be able to arrange a setup which takes your incoming antenna signal (which will consist almost entirely of ATSC signals), buffers/amplifies it, mixes in a modulated NTSC signal from the DVDR modulator (on a channel not used for ATSC), and distribues this out to all of the TVs. Tune to an ATSC channel and they'll detect and decode the corresponding digital signal. Tune to the channel you're using for NTSC analog from the DVDR, and that's what they'll show.

This will be *much* less expensive than trying to take the analog output of the DVDR, encode it into ATSC digital format, modulate it, and mix it onto the cable.

The best video quality from the DVDR would be via HDMI (or component, or S-Video, or composite, in that rough order) rather than via modulated RF (which is often soft and blurry looking) but you'd need home-run cables from the DVDR and some form of distribution amp to do these.

--
Dave Platt                                    AE6EO
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     boycott any company which has the gall to send me such ads!

Not around here. Digital only TVs are starting to proliferate since analog TV is no longer broadcast, it makes little sense to pay for obsolete technology any more. They only have Scart inputs, so if you want to tune to VHF/UHF you will need an external analog tuner.

Only if you are willing to settle for 'less than analog boradcast quality signals'. Recall that anyone who compared the quality of the RF signal output of a VCR to the composite signal quickly decided that it was worth buying the composite cables. And a component connection offers even better performance.

Also, unlike others, I do a little research. The last two DVD players I purchased don't even have RF outputs. One, a Toshiba, DOES have an HDMI output.

Doing a little research, the ZvBox® 170 appears to do exactly what the OP proposed. Not surprising, that's what it was designed for.

PlainBill

Well try reading what is posted instead. It was stated that the best quality video would be with HDMI, with component, S-Video, composite and RF trailing in descending order. Correct statement. Not sure how your "boradcast" signals would differ (if at all.)