Alternatives to BTSC/MTS for analog stereo? - AVS Forum
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post #1 of 7 Old 09-13-2012, 02:18 PM - Thread Starter
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I'm a newbie at this, but I'm surprised how few solutions exist for modulating stereo audio onto an RF signal to send through RG6 cable. BTSC/MTS would seem the obvious solution, but RF modulators with this option are rare and ridiculously expensive - like 4x the cost of an equivalent modulator without BTSC/MTS. I understand (from Wikipedia) there were patent issues until 2004, and that there are still a few patents regarding digital modulation, but it seems that some years ago, both BTSC modulators and BTSC converters for mono modulators were both less expensive and more widely available. I wish I'd bought back then, but apparently today it's too late. WTF happened? Did BTSC/MTS just fall out of favor because anyone that might have been interested now wants full-blown HD with DD 7.1 instead?

Anyway, we are where we are, I guess. Given that BTSC is out, what alternatives are there? The constraint is that I'd like to add SD video and stereo audio to an existing RG6 cable system which currently carries OTA digital TV; i.e., I don't want to rewire my home with additional cables. (If it weren't for the stereo requirement, an ordinary RF modulator would do the trick.) Also, the A/V needs to be sent to multiple rooms, so wireless devices are out unless they allow multiple receivers per transmitter.

I'm vaguely aware of HPNA and MoCA, although they seem like overkill for this. But if you think they're the best solution, let me know.

I also thought of a DIY solution: use FM stereo instead, a la those old cable/FM simulcasts from the 80's. But that'd require both an FM radio and a video tuner for each channel; things would quickly get pretty bulky at the receiving ends.

So; what do you all think?
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post #2 of 7 Old 09-13-2012, 09:16 PM
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There were some very inexpensive ch3/4 MTS modulators at RadioShack a while ago, but I suspect they're long gone from the lineup.

A ChannelPlus SVM22 would be the best bet - here's a site that claims to have some for cheap:

http://www.tselectronic.com/shop/product/Channel-Plus-SVM22-2-Channel-MTS-Stereo-Modulator/239

(I know nothing about this site other than it came up in Google...)

MTS was never a strong requirement for residential RF modulators, so I suspect it never made it into the low-end chips to get the price in-line with comparable non-stereo modulators. But then again, the whole market for residential modulators was never big to begin with... And of course, this stuff is now all functionally obsolete.

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post #3 of 7 Old 09-14-2012, 07:41 AM - Thread Starter
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Quote:
Originally Posted by jautor View Post

There were some very inexpensive ch3/4 MTS modulators at RadioShack a while ago, but I suspect they're long gone from the lineup.
A ChannelPlus SVM22 would be the best bet - here's a site that claims to have some for cheap:
http://www.tselectronic.com/shop/product/Channel-Plus-SVM22-2-Channel-MTS-Stereo-Modulator/239
(I know nothing about this site other than it came up in Google...)
MTS was never a strong requirement for residential RF modulators, so I suspect it never made it into the low-end chips to get the price in-line with comparable non-stereo modulators. But then again, the whole market for residential modulators was never big to begin with... And of course, this stuff is now all functionally obsolete.
Jeff
Thanks. I remember reading that RS briefly had an MTS stereo modulator circa 2003. That would've jumped the gun on the patents and they quickly jerked it off the market. It was gone before I even knew it was there. I wish they'd put it back in their lineup after the patents expired in 2004, though.

That SVM-22 at the link looks like a good deal. Summit Source has it also, but it's over $200. TS Electronics has a surprisingly low price considering the (lack of) competition. I suppose the S-video inputs are merely for convenience, since once you modulate it, it's not going to look any different from composite. But the SVM-22's A/V cable pass-through and IR forwarding features are nice, and it's a 2-channel modulator, so each one is "really" under $100 wink.gif

MTS may be obsolete but it can't be beat when trying to get the most out of other obsolete equipment. My primary video source is an old Dish SD satellite receiver which I have no plans to upgrade, and I have an old Sharp 19" analog TV with only an RF input in the guest bedroom, so my only options for stereo in that room are MTS or a separate speaker system.
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post #4 of 7 Old 09-14-2012, 08:20 AM - Thread Starter
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One weird thing about Channel Plus modulators is that they go up to cable channel 125, but only to UHF channel 64. Apparently there's no UHF/Cable switch - it just assumes if you set a channel number over 64, you mean cable!

That's not a terribly big deal - it just means I have to set my receivers to cable instead of antenna if I want to use the top of the 700 MHz band. But it does make me wonder about low-pass filters.

I assume I'll need a low-pass filter to remove 700 MHz-band "noise" coming from my antenna; otherwise my new stereo channels will be snowy. But Channel Plus sells only 600 MHz (which would obliterate about 17 OTA channels) and 750 MHz, which they say makes room for UHF channels 65 & up (which the SVM-22 won't do) or cable channels 121 & up (which is what I'd use). But given the digital transition, why don't they make a 700 MHz filter? If it had a similar roll-off, that would open up about 8 more channels. Heck, even a 720 MHz filter would open up 5 more channels.

Pico-Macom does make a Tru-Spec 700 MHz filter, but it claims to have a slow roll-off that only partially blocks frequencies below 800 MHz. (Also I'm concerned it might start rolling off a bit too soon and screw up channel 51.) Has anyone tried either filter? Do they work better/worse than advertised?
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post #5 of 7 Old 09-21-2012, 07:23 AM - Thread Starter
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Quote:
Originally Posted by JHBrandt View Post

MTS may be obsolete but it can't be beat when trying to get the most out of other obsolete equipment. My primary video source is an old Dish SD satellite receiver which I have no plans to upgrade, and I have an old Sharp 19" analog TV with only an RF input in the guest bedroom, so my only options for stereo in that room are MTS or a separate speaker system.

They shipped my SVM-22 the day before yesterday. As a test, I hooked it up in the guest bedroom between an ordinary converter box and that Sharp TV with only an RF input. Works great. It was nice to see the "stereo" indicator light come on for the first time since 2009 biggrin.gif

I also noticed something I didn't expect: the picture quality seemed better too. Specifically there seems to be more color saturation, and boundaries (as between color bars) seem sharper & clearer with less bleeding, than with the previous RF modulator (a UHF modulator Radio Shack used to sell).

Maybe that's just my imagination. After all, picture quality is subjective, and I did pay a lot for the SVM-22, so maybe I'm just seeing what I want to see. But could a better RF modulator really make a noticeable difference?
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post #6 of 7 Old 09-21-2012, 09:19 AM
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Originally Posted by JHBrandt View Post

I also noticed something I didn't expect: the picture quality seemed better too. Specifically there seems to be more color saturation, and boundaries (as between color bars) seem sharper & clearer with less bleeding, than with the previous RF modulator (a UHF modulator Radio Shack used to sell).
Maybe that's just my imagination. After all, picture quality is subjective, and I did pay a lot for the SVM-22, so maybe I'm just seeing what I want to see. But could a better RF modulator really make a noticeable difference?

Yes, it most certainly will make a noticeable difference in quality. The filters and insertion circuits are back in the black art of analog - there was a big swing between cheap consumer-grade modulators and the broadcast-grade frequency-agile (or dedicated freq) gear. The ChannelPlus stuff is much closer to the "right" end of that spectrum! biggrin.gif


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post #7 of 7 Old 09-21-2012, 12:45 PM
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You'll love your SVM-22. I have a couple of MTS modulators (5615, 5625 -- pre-SVM models). Still going strong after all of these years. One thing I sometimes forget, though: if video is lost, the audio is muted. It's a good thing, but you can go crazy troubleshooting no audio if you forget that. wink.gif

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