RF Modulator with S-video line-in or composite line-in?

[Disco Makberto]

Dear e-readers,

I have a SD analog television that I am planning to use in conjunction with an RF modulator, for that television only has an RF-in connector. My question is simple. The line-in of the RF modulator will be either S-video or composite coming from the same source, but which one is better for my set up? Should I use the S-video line-in to the RF modulator or the composite line-in to the RF modulator?

I believe it is better to use composite than S-video. Technically, S-video is supposed to be better than composite, but in my set up, one or the other will be transformed into RF which means that the separate video as S-video will be combined into one causing degradation while the already-in-one video signal as composite will be used as it is in the transformation into RF. Of course, the final RF signal will also include audio, but the incorporation is the same for both S-video and composite.

Please be so kind to post your opinions on this issue, and I hope I am using the correct terms.

Carlos Albert
Disco Makberto

[lordsmurf]

I don't think it will really matter.

[Disco Makberto]

Hey, Lordsmurf!

Glad to see you here.

When you mean that it doesn't matter, do you mean that it doesn't matter because there won't be any degradation from S-video to RF or from composite to RF? Or do you mean that, even though there is degradation from S-video to RF like I suppose or from composite to RF, the degradation won't be noticeable at all. Technically speaking, I am not sure if there is degradation or not or up to what point there is such, but it seems to me that there is less degradation going from composite to RF.

Carlos "DM" Albert

[Number Six]

I don't think it will really matter.

I agree with lordsmurf - your final output to the TV will be RF, which is the lowest quality that you can send to the TV. If it were the other way around - splitting RF down to composite or S Video, S video going into the TV would be slightly better.

[edDV]

The weak point is the cheap RF modulator.

Composite NTSC gets modulated onto RF (vestigial AM sideband for video and FM for audio).

S-Video Y/C would first be added to make composite NTSC and then modulated onto RF.

The resulting Ch3 or Ch4 look like this.

[Disco Makberto]

Hey, fellows!

I agree that RF is the worse signal of all, but making it less worse is better than making it more worse.

EdDV says,

"Composite NTSC gets modulated onto RF (vestigial AM sideband for video and FM for audio).
S-Video Y/C would first be added to make composite NTSC and then modulated onto RF."

This proves my point, or so I hope. There is more conversion going from S-video to RF as opposed to going from composite to RF, and, by definition, there is more degradation by going from S-video to RF as opposed to going from composite to RF. Whether the final RF output will look the same to me via one way or via the other is not my point, but rather whether there is more degradation via one way or via the other, technically speaking.

Cheers,

CAL-DM

[Disco Makberto]

P.S.: Perhaps the degradation would be barely noticeable if I use a really big RF-only television.

[prouton]

The problem lies not in the conversion from either s-video or composite, but in the modulation into an RF signal. These days, RF modulators are hard enough to come by, because there's so little need for them. With so little demand, there's no reason to market a really good unit, i.e., one that creates a really clean signal. There just aren't very many people who'll shell out $100 or more for such a unit in order to get first rate components, design and construction. Instead, you get cheap to build $30 units that create a high profit margin (to cover spending months on the store shelf) -- and that deliver blurry results. They'll work in a pinch, but that's about all you can expect.

Got an old VCR laying about? Try running the composite signal through that to the RF input on your television. See if the results are acceptable, and if they are continue to use it. Seems like overkill, I know, but the electronics are apt to be better than a stand-alone converter.

[edDV]

No there is no advantage to using S-Video in this case. The consumer modulators are crap.

If you really want a quality RF modulator, many multi-thousand dollar broadcast units become available after the Jun12 broadcast analog shutdown.

Some TV stations might just give it to you. You will be ebay bidding against latin american and canadian TV stations.

[Disco Makberto]

Good points, so what pro or semi-pro RF modulator(s) do you recommend?

To set the record straight, if I use a pro or semi-pro RF modulator, it is better to use composite to RF instead of using S-video to RF because there is more degradation in S-video to RF.

Carlos Al "D-Mak"

[Disco Makberto]

P.S.: If I connect a video signal by going S-video to VCR or composite to VCR which in turn creates an RF signal, I still can use the RF modulator. When connecting an RF signal to an RF modulator, the signal just passes through without any conversion, in other words, it goes RF to RF. Thanks!

[samijubal]

If you're talking about using a DVD player you probably can't connect through a VCR without copy protection problems.

[yoda313]

@disco makberto - I'm not sure if I was following right but if you were to use a vcr as suggested you would just connect the coax (rf) directly to the tv without an intermediate converting device. That is assuming that the destination is the tv itself. If there is an intermediate destination than that would be correct.

Also point of warning on using a vcr as a modulator you may get macrovision issues depending on the vcr. It may not like a dvd signal for instance. it could pass it through but some models will present an alternating dark and light pattern making it very difficult to watch (the original signal being ok but the playback will go from bright to dark and back again).

Just fyi.......

EDit samijub beat me to it - however I know there are some brands and models (won't name them in the open) that don't have macrovision issues. PLus there are devices that can defeat them but again I won't get into details. Doing a net search on it will reveal solutions....

[Disco Makberto]

No, the original source would be a computer that can output as S-video or composite. But your point is well taken. As a matter of fact, now that I am thinking, if I use the DVD player of my computer and connect it through a VCR, I will surely have those copy protection problems you are mentioning. I think they are called macrosplat. So, I appreciate your help.

CAL

[yoda313]

think they are called macrosplat.

Actually its Macrovision - sorry if you're trying to be funny I don't mean to be too straight on it....

EDIT - don't forget macrovision will only affect commercial dvds. If you're trying to computer gaming that doesn't have copy protection and would pass through all right - at least I've never heard of a video game with macrovision - at least not a computer game....

[Disco Makberto]

Yoda 313 says,

"@disco makberto - I'm not sure if I was following right but if you were to use a vcr as suggested you would just connect the coax (rf) directly to the tv without an intermediate converting device."

And RF modulator is not a converting device when is fed with an RF signal. It just passes the RF signal as if it were connected directly to a television.

"That is assuming that the destination is the tv itself. If there is an intermediate destination than that would be correct."

The destination is the television itself, but I want to use an RF modulator because I can mix different sources, for instance, one source can be a computer, another source can be a cable TV feed (already converted to analog after June 12), still another one can be a DVD player, etc.

"Also point of warning on using a vcr as a modulator you may get macrovision issues depending on the vcr. It may not like a dvd signal for instance. it could pass it through but some models will present an alternating dark and light pattern making it very difficult to watch (the original signal being ok but the playback will go from bright to dark and back again)."

Indeed, and I hadn't thought of that.

"Just fyi.......
EDit samijub beat me to it - however I know there are some brands and models (won't name them in the open) that don't have macrovision issues. PLus there are devices that can defeat them but again I won't get into details. Doing a net search on it will reveal solutions...."

Thanks for the info.

I hope that edDV or another reader can advise me on some professional or semi-professional RF modulators that perhaps I can get for a cheap price on auction sites.

Carlos Albert L.
Disco Makberto

[Disco Makberto]

Hey, Yoda313!

"Actually its Macrovision - sorry if you're trying to be funny I don't mean to be too straight on it...."

Macrosplash is the term used on a site that sells converter boxes and alike.

I am familiar with the term macrovision, but I thought that that was applied to VHS tapes only, and not to the process itself.

"EDIT - don't forget macrovision will only affect commercial dvds. If you're trying to computer gaming that doesn't have copy protection and would pass through all right - at least I've never heard of a video game with macrovision - at least not a computer game...."

I didn't know that computer games on DVD's were not macrovision-protected.

Carlos Albert
D-M

[edDV]

I can only think of two reasons to ever use NTSC RF as an output.

1. Yout grandma's old TV only has RF in.

2. You want to feed video to the other side of the house on coax but don't want to use WiFi, Ethernet or separate A/V cables.

[olyteddy]

Some of the CATV modulators I've worked with define 'Composite Video' as Video with the Audio alraedy muxed onto it. The full 6 MHz.

[edDV]

Some of the CATV modulators I've worked with define 'Composite Video' as Video with the Audio alraedy muxed onto it. The full 6 MHz.

Yeah, that is on the cable company side of the cable box. The modulators being discussed above are the Ch3/4 consumer models like these.

http://www.amazon.com/Philips-PH61159-RF-Modulator/dp/B0001GGXQI
http://www.walmart.com/catalog/product.do?product_id=2181628
http://www.provantage.com/belkin-f8v3063~7BELC15A.htm
http://www.amazon.com/RCA-CRF940-Modulator-Gold-Plated-Connectors/dp/B00008X5DD

[Disco Makberto]

EdDV says,

"I can only think of two reasons to ever use NTSC RF as an output.
1. Yout grandma's old TV only has RF in.
2. You want to feed video to the other side of the house on coax but don't want to use WiFi, Ethernet or separate A/V cables."

Bingo! Exactly those two reasons are why I want to use the set up I am describing. Just replace "grandmother" with "mother".

Carlos Albert
D-Makberto

[Disco Makberto]

Re: Cable TV boxes.

It is my understanding that cable TV boxes are not modulators but demodulators, at least the traditional ones. They take an RF signal and demodulate it into composite, for instance. One cable box that I have also demodulates into VGA which I find interesting.

Carlos Albert
Disco Makberto

[jagabo]

And then the Cable TV box remodulates back onto channel 3/4 when using the RF (coax) output.

[Disco Makberto]

Good point, Jagabo! So these "dual" boxes are actually modulators/demodulators or "modems" (:

[Disco Makberto]

Re: Pro or semi-pro RF modulators.

After some research, I have some some pro or semi-pro models by Pico Macom and Blonder-Tongue. Can anybody of you recommend me another one(s)? I will probably go for the semi-pro simply because they are usually cheaper.

Carlos Albert Lacaye
Disco Makerto

[edDV]

Re: Cable TV boxes.

It is my understanding that cable TV boxes are not modulators but demodulators, at least the traditional ones. They take an RF signal and demodulate it into composite, for instance. One cable box that I have also demodulates into VGA which I find interesting.

Carlos Albert
Disco Makberto

Analog cable boxes do the same job as TV tuners. Both tune 6MHz channels from RF spectrum (in NTSC land) and then demodulate the selected channel into composite NTSC, S-Video (Y/C) and separate stereo audio. TV sets also decode NTSC into RGB for display.

Consumer modulators convert separate composite or Y/C video and audio into modulated Ch3 or Ch 4. Pro modulators can convert to any channel in the spectrum. A cable company needs a modulator for each channel offered.

With broadcasting and most of cable going to digital modulation, many pro analog modulators are hitting the surplus market. Good time to build your own analog cable system :P

[lordsmurf]

Use RG6 cable instead of RG59, if you have the choice with the coax connection being made.

[Disco Makberto]

EdDV says,

"Analog cable boxes do the same job as TV tuners. Both tune 6MHz channels from RF spectrum (in NTSC land) and then demodulate the selected channel into composite NTSC, S-Video (Y/C) and separate stereo audio. TV sets also decode NTSC into RGB for display."

Interestingly, one analog Novavision cable box I have demodulates into VGA. I suppose that this is to watch cable televison on a computer monitor.

Carlos Albert L.
D-M

[Disco Makberto]

Lordsmurf says,

"Use RG6 cable instead of RG59, if you have the choice with the coax connection being made."

Thanks, Lordsmurf! I will do that.

Thumbs up,

Carlos Albert
Disco M.

[edDV]

EdDV says,

"Analog cable boxes do the same job as TV tuners. Both tune 6MHz channels from RF spectrum (in NTSC land) and then demodulate the selected channel into composite NTSC, S-Video (Y/C) and separate stereo audio. TV sets also decode NTSC into RGB for display."

Interestingly, one analog Novavision cable box I have demodulates into VGA. I suppose that this is to watch cable televison on a computer monitor.

Carlos Albert L.
D-M

Yes, that is rare. VGA is a form of analog RGB but is not locked to the TV line structure. Usually video is clocked into a frame buffer, then read out with a RAMDAC similar to a computer display card. There is quality compromise using this method.
http://en.wikipedia.org/wiki/RAMDAC