two tuners (set-top box and DVR) - AVS Forum
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post #1 of 5 Old 10-17-2010, 02:45 PM - Thread Starter
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I have some questions concerning the use of a cable set-top box and a DVR.

Early last year, we bought a Magnavox H2160MW9 DVR, after some very useful
discussions from this forum. The DVR has been great. Believe it or not, we
are just now going to upgrade to digital cable TV (Time-Warner, USA). As I
understand it, the antenna signal will still contain both the analog channels
(NTSC) and the digital ones (QAM, scrambled). The set-box will be needed for
unscrambling. I imagine using the RF connectors to pass the antenna signal
through the set-top box into the DVR. I haven't been able to see the set-box
yet or find its specs online.

Questions ...

1. I'm unclear on how the two tuners (set-top box, DVR) will function
together. Imagine wanting to see a scrambled channel. For that at least,
I imagine the set-top box will need to be on. Does the RF out of a
typical set-top box continue to send out a multiplex of all channels (now
all unscrambled), from which one is selected by the DVR tuner? If it
sends out just the channel selected by the box tuner, is the DVR tuner
ignored?

2. In the latter case, it seems that if I want to do a timer recording, I'll
need to leave the set-top box on and set to the desired channel. This
would preclude a run of several timer recordings on different channels.

3. In the DVR manual (connections, p. 17), it says to make component or S-
video connections between the set-top box and the DVR. I'm not sure what
signal comes from the set-top box on those lines. Maybe those just carry
the one channel selected by the box's tuner. Or maybe some boxes play
discs and use those outputs.

Thanks.
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post #2 of 5 Old 10-17-2010, 03:09 PM
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First off, DVRs are Digital Video Recorders, the non-DVD burning hard drive equipped set top boxes leased by cable companies. The Magnavox you own is a DVDR or DVD recorder. It's important to distinguish between the two.

Quote:
Originally Posted by kleene View Post

1. I'm unclear on how the two tuners (set-top box, DVR) will function
together. Imagine wanting to see a scrambled channel. For that at least,
I imagine the set-top box will need to be on. Does the RF out of a
typical set-top box continue to send out a multiplex of all channels (now
all unscrambled), from which one is selected by the DVR tuner? If it
sends out just the channel selected by the box tuner, is the DVR tuner
ignored?

The set top box does all the tuning. It's outputs are only the one channel it is currently set to. The DVD recorder's tuner is ignored.

Quote:



2. In the latter case, it seems that if I want to do a timer recording, I'll
need to leave the set-top box on and set to the desired channel. This
would preclude a run of several timer recordings on different channels.

Pretty much. Older recorders had what was called an IR blaster that allowed them to change a set top box's channels.

However, if the cable box has a program guide, you can set that to change the channels while the recorder records whatever it receives from the box.

Quote:


3. In the DVR manual (connections, p. 17), it says to make component or S-
video connections between the set-top box and the DVR. I'm not sure what
signal comes from the set-top box on those lines. Maybe those just carry
the one channel selected by the box's tuner. Or maybe some boxes play
discs and use those outputs.

It's the same one channel output that the RF should be outputting, but usually the picture is better. S-video is the top input for your recorder. Composite is next in line, RF dead last. I would use S-video if available.

Don't believe everything on the Interwebz! A duck's quack DOES echo!
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post #3 of 5 Old 10-17-2010, 03:29 PM
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If I understand you correctly, my setup might help you with yours. I have Cox digital cable, which means I have a set top box needed to unscramble the channels Cox includes with that package. These are the the higher numbered stations for me, but I guess that could vary depending on the cable system.

I have several Panasonic and one Magnavox dvd recorder in the room with the cable box. As was said earlier, if you use the cable box as the tuner, you have the choice of recording one station no matter how many recorders you have. And if you are going to record a scrambled station, for me something above channel 99, then you have to use the cable box as a tuner and set both it and the recorder's timers.

However, I found I also record a lot from stations that are on stations below 99, including the networks, USA, TNT, etc, so I simply split the coax feed coming from the wall into two. One I ran into the cable box. Then from the cable box I ran sound and video, using a S-video cable, to a Radio Shack signal distributor. That gave me four outputs which I then ran using a/v cables to the line inputs of the Panasonic recorders.

By doing that, I can still record only one scrambled station at a time, but I can control which machine I record on, since I like to use different units for different types of programming (sports on one machine; movies on another, that sort of thing).

The other split from the original wall coax I have going into the RF inputs of the recorders. This allows me to record DIFFERENT stations concurrently on different machines, using their tuners only, since I'm bypassing the cable box.

Finally, I also have a cheap antenna in the room that receives over the air HD signals from the networks (plus a few odd ball stations). These pictures are very good and I use that feed by splitting the signal coming in into a couple of newer Panasonic recorders with ATSC tuners, and into the Magnavox, which also has an ATSC tuner. Great picture quality.
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post #4 of 5 Old 10-17-2010, 03:48 PM
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Here's a help file for the Mag recorder on recording from a STB, followed by some TIPS from other users on how you can coordinate timer recordings between the two. Could be some "surprising" stuff for STB users.

See Sketch 3 here for a Basic and an Advanced connection scheme for the Mag with lots of text esplaining it all.
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post #5 of 5 Old 10-17-2010, 04:49 PM - Thread Starter
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Thanks to all of you for the quick responses. The posted help files look
terrific. I'll wade through them and see how it goes once we buy into
digital service.
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