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Old 01-26-2013, 01:47 AM   #1
WPe
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How to Minimize Signal Loss with So Many Devices?

Picture quality using only a Tivo HD with cable card & tuning adapter works without issue if that is all that is connected. Channel meter lists the various channels at 80 something.

However, I also have a cable modem and a thingy for cable telephone service. If I use the splitter they installed, the Tivo signal meter can go down to the 40's, and the picture can become tiled and break up. Not always but enough for it to be annoying. Obviously, the internet connections drops too often when the signal is this low. I have another cable line on another floor and the signal loss is a little better. Channel meter might go to the 40's as well when split, but at least the picture does not break up as often.

Hence the question: How can I mimimize signal loss so that I can use the line for both tv and modem/telephone? I would be happy with one line getting tv + cable modem, while the other line gets the tv + telephone adapter. Am I going to have get the cable company to install a line for each device?

Thanks for reading this and for any advice that you can give me.
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Old 01-26-2013, 02:44 AM   #2
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Get a bidirectional amplifier - the signal comes to your house with a certain strength, and each split attenuates the signal sum. For best results, put the amplifier very early on - you want to amplify prior to the split.

The bidirectional is required for the upstream data connection. Some amplifiers don't amplify the upstream part, others do.

If you look at the splitters, you'll find markings on each output port like "-3db" or "-6db". That indicates how much the signal is attenuated through the splitter to that port as compared to the input port. Your amplifier should ideally be at least able to amplify the signal by roughly that much (so if it's a -6dB splitter, you should find an amp that can amplify by at least 5dB in the forward (54-1000MHz) direction).

Note that the upstream is also attenuated by that much going up and if your amplifier doesn't amplify the upstream, it will also attenuate anywhere from -3dB to -6dB. Depending on your telephone and modem specs, it may have no effect or big effect depending on if those devices can crank their output power to compensate.
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Old 01-26-2013, 03:18 AM   #3
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The other end of the line(s) is the locked cable box. There is no split before that. Will a bidirectional amplifier still help?
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Old 01-26-2013, 09:35 AM   #4
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I think the real answer here is your cable co needs to provide a stronger signal into your structure to begin with, and if they can't THEY should provide the amplifier (definitely bi-directional of course -- they should know that since their STB's and DVR's use the same signals as TiVo's).

It's quite common for homes to have several drops, splitters, etc. The incoming cable signal should be strong enough to support this.

Apply maximum pressure to your cable co to improve this, before you go to any trouble or expense.
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Old 01-26-2013, 07:28 PM   #5
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I got a whole house bi-directional cable amplifier from my cable company for $45 and have no problem driving six outlets, some with splitters on them.
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Old 01-26-2013, 11:28 PM   #6
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In my experience, TiVos need a cleaner, stronger signal that any cableco equipment, so I put a 1:2 splitter that feeds TiVo and then a 1:2 (or more) splitter that feeds my cable box, tuning adapter, and TV.
That way the TiVo only gets a single -3dB drop from the incoming line and the other equipment sees more but seems fine.
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Old 01-28-2013, 03:30 PM   #7
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As I said, there is no other split on the line until I reach the locked box. So it sounds like an amplifier will not be of much use.

As-is, the line is only split right next to the Tivo & cable modem. One split goes to the Tuning Adapter. The other split goes to the cable modem.

I have heard of some people with a Centon or whatever cablecard solution splitting the cable where one split goes to the Tuning Adapter, and one split going to the Centon. Is that possible with a Tivo HD? Meaning, will it work if I split the cable with one cable going to the Tivo, and one going to the Tuning Adapter with the USB cable connecting the two?

I am wondering if there is signal loss because the line first goes to the Tuning Adapter before it goes to the Tivo.
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Old 01-28-2013, 05:26 PM   #8
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Quote:
Originally Posted by WPe View Post
As I said, there is no other split on the line until I reach the locked box. So it sounds like an amplifier will not be of much use.

As-is, the line is only split right next to the Tivo & cable modem. One split goes to the Tuning Adapter. The other split goes to the cable modem.

I have heard of some people with a Centon or whatever cablecard solution splitting the cable where one split goes to the Tuning Adapter, and one split going to the Centon. Is that possible with a Tivo HD? Meaning, will it work if I split the cable with one cable going to the Tivo, and one going to the Tuning Adapter with the USB cable connecting the two?

I am wondering if there is signal loss because the line first goes to the Tuning Adapter before it goes to the Tivo.
That is actually the preferred solution. There is signal loss going through the TA. You only need the USB to communicate between the TA and the TIvo.

You still may want to or need to put an amplifier in. Or as suggested, get the cable co. to put one in. Should be free, they are responsible to give you a good signal.
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Old 01-28-2013, 07:13 PM   #9
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That is actually the preferred solution. There is signal loss going through the TA. You only need the USB to communicate between the TA and the TIvo.

You still may want to or need to put an amplifier in. Or as suggested, get the cable co. to put one in. Should be free, they are responsible to give you a good signal.
Actually Cisco TA's (STA1520) provide a small gain for the signal going through them, while Motorola TA's have a small loss. In either case, splitting the signal between TA and TiVo is not going to give you stronger signal into the TiVo. I know some people prefer the splitter configuration but it's not because it gives you a stronger signal into the TiVo -- actually I've never understood what the expected advantage is.
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Old 01-29-2013, 01:51 AM   #10
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Yeah, the splitter method just consumes more coax cable - after all, you need two pieces of coax extra - the one from the wall goes tot he splitter, then one goes to the TA, the other to the TiVo. The passthrough is far cleaner and less messy - the cable from the wall goes to the TA, then another one goes from the TA to the TiVo.

The expected advantage may be a slightly stronger signal - a splitter with two ports normally gives a 3dB loss through each port. If the TA you have provides a loss greater than 3dB, then it will have a stronger signal. If it has less, or the TA has an amplifier, then the advantage is nil.
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Old 01-29-2013, 09:19 AM   #11
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IIRC neither TA type has anything close to a 3 dB insertion loss.
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Old 01-29-2013, 07:36 PM   #12
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I think the advantage of splitting before the TA is supposed to be that you can still watch non SDV channels if the TA is off. If you don't split you lose all channels if the TA is unplugged.

I don't have mine set up that way (been too lazy to change it) but that's what I understand to be the case.
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Old 01-29-2013, 07:49 PM   #13
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According to a TiVo tech that I dealt with a few months ago the signal should be between 90 and 95 on the channels. Any higher and it can cause problems as would a signal lower than 90. You might want to check the cables you are using and upgrade to quad 6. Also check the connectors. If one of them isn't crimped correctly you will also get a loss.
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Old 01-30-2013, 10:28 AM   #14
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That TiVo tech's advice is in major conflict with what tivo says on their support pages:
http://support.tivo.com/app/answers/.../150/kw/signal
If you expand at the right point there, you find a chart showing minimum and recommended sig strengths for S3, HD and Premiere Tivos. The recommended range is 80-99 while the minimum is 50, except 70 for the S3. (This is for QAM256, the most common modulation format.)

I've experimented with different inline attenuators. There is no way I can get all my channels in the recommended range. About half of them are saturated at 100 and still some of them are around 80 and one or two are lower. I see major pixellation if the sig strength is below 50, in agreement with TiVo's chart. I believe there are no problems if the sig strength is only slightly above 100, but you have to experiment with attenuation to know they are only slightly above 100. For example, if a channel is 97 with a 6 dB attenuator then you can reason it will only be slightly above 100 with no attenuator. Signals way in excess of 100 can cause video dropouts due to protection mechanisms in the TiVo's circuitry (this also from their support page).

In principle I should demand my cable co remove the excess "tilt" from my signals (so I could get them all between 80 and 99). But my confidence level with TWC support is if I request this I am much more likely to get either no response or a response that makes things worse. As long as I can work around their tilt I will leave it alone. It has often been said on this forum that TiVo tuners are more sensitive to varying signal levels than TV's and cable co STB's and DVR's. Based on that, the tilt I experience may be within what TWC considers as acceptable limits -- just not optimum for TiVo.
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