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RF modulator on digital cable?

post #1 of 9
Thread Starter 
I've searched the forums for similar ideas, but I think what I want to do are slightly different. Let me know if I'm wrong!

I'd like to RF modulate the output of a security DVR onto my OptimumOnline digital cable network. Ideally, the channel would be viewable via both the cable box (SA 8300HD in the family room) and my cable-ready TV (bedroom), but I'm fairly certain that the cable box won't see an analog channel. To overcome this, I thought I would use the old VCR still connected to an aux input to the family room TV.

My problem is that I can't find any definitive information about the digital cables frequency usage. Can I insert a channel using my HMM-10H RF mod (CH14-CH83 or CH65-CH139) with an RF dist amp (HVM-1308) and the appropriate notch filter, onto the digital cable without interfering with digital channels or the cable modem? And if this works, will it still work after the digital changeover in June?

Thanks.

tom
post #2 of 9
Without knowing exactly where the QAM channels are I would say you are asking for trouble.

Oh and digital cable has nothing to do with the digital TV conversion that was pushed back to June.
post #3 of 9
Do you have access to a spectrum analyzer?
post #4 of 9
Thread Starter 
Quote:
Originally Posted by 11001011 View Post

Oh and digital cable has nothing to do with the digital TV conversion that was pushed back to June.

True, but I read (somewhere on these forums) that after the changeover that some cable co's are planning to reshuffle the cable frequencies assigned to the analog channels and I thought that might impact what I'm trying to do.

RCbridge: Yes. I have an 8591E at work that I use for RF design. Tell me more...

tom
post #5 of 9
Your HMM-10H goes up to 860MHz, and more likely than not, your cable system goes up to 750MHz. You could get an LPF-750 and tune your HMM-10H to something above ~780MHz (~channel 122) or so and connect the modulator via a DC-12. The cable would go into the LPF, which connects to the DC-12's OUT leg. The HMM-10H connects to the TAP leg of the DC-12, and the IN leg goes to your distribution system.
post #6 of 9
Quote:
Originally Posted by embedded_tom View Post

True, but I read (somewhere on these forums) that after the changeover that some cable co's are planning to reshuffle the cable frequencies assigned to the analog channels and I thought that might impact what I'm trying to do.

Yes, no, maybe... That's sort of the problem. Cable systems are considered a private network and do not have to follow all same exact rules and regulations as broadcast TV.

Cable can go all digital anytime they want or never. But I do think the FCC has requested they keep the "lifeline basic service" (Ch2-Ch13) analog for a while longer.
post #7 of 9
Quote:
Originally Posted by 11001011 View Post


Cable can go all digital anytime they want or never. But I do think the FCC has requested they keep the "lifeline basic service" (Ch2-Ch13) analog for a while longer.

Unless a system is already all digital, they must transmit the locals in analog for until 2012.
post #8 of 9
Thread Starter 
Quote:
Originally Posted by egnlsn View Post

Your HMM-10H goes up to 860MHz, and more likely than not, your cable system goes up to 750MHz. You could get an LPF-750 and tune your HMM-10H to something above ~780MHz (~channel 122) or so and connect the modulator via a DC-12. The cable would go into the LPF, which connects to the DC-12's OUT leg. The HMM-10H connects to the TAP leg of the DC-12, and the IN leg goes to your distribution system.

Whoa! I was thinking that the RF mod would be inserting a channel before the cable frequencies, not after. Cool.

But do I really need a DC-12? My distribution box (it's amplified) has two auxiliary inputs just for this purpose (RF modulators).

Quote:
Originally Posted by 11001011 View Post

Yes, no, maybe... That's sort of the problem. Cable systems are considered a private network and do not have to follow all same exact rules and regulations as broadcast TV.

Cable can go all digital anytime they want or never. But I do think the FCC has requested they keep the "lifeline basic service" (Ch2-Ch13) analog for a while longer.

Hmmm. It sounds like I might be able to make something work for now, but not for the long term.

Thanks for the info everyone. I think I'll look to other means of accomplishing this idea.

tom
post #9 of 9
If your distribution amp has a couple of inputs for modulators, no, you would not need a DC-12. You may, however, need to pad down the output of the modulator. It puts out 25dBmV, and even with the internal combining network of the amp, that may still be too much.
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