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Old 12-12-2013, 09:19 PM   #1
kbmb
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Question about signal and the Roamio

Trying to figure out if this is a Roamio issue or a cable amp issue.

I've mentioned in the past I have a 4 port amp that boosts the cable signal in the house. One of those runs is to a Roamio Plus. Generally I have 100% signal strength and 43 SNR. I don't care what Tivo says about those numbers, I had them for 8 years with the Tivo HD and so far with the Roamio and have not had any issues with picture quality, or tuning and all 6 tuners work great (no tuning adapter here).

Anyway....I've had some random Roamio reboots like others have had. So occasionally I check the DVR diagnostics to see what the uptime is on the cable card to see if it rebooted....just because I'm nosey ;-) Tonight I went to check and noticed that my signal levels were down.....some channels into the 70% range with 36 SNR. Now for me on some cable channels like FOOD and A&E, these lower numbers mean I get pixelation.

Now when this happened in the past it was when I was setting things up, and to fix it before I simply unplugged the feed into the cable amp and plugged it back in.

Well tonight when the numbers were down, I did just that. I simply unplugged the incoming coax to the cable amp for a second and plugged it back in. I did nothing else. Well, all signal levels in the Roamio returned to 100% and 43 SNR.

Anyone have any ideas....is this a cable amp issue or a Roamio issue.

BTW, it's been months since this last happened.

I'm just trying to figure out if for some reason the Roamio starts to pull in weaker signals and the unplugging/replugging resets the tuners? Or does this indicate the amp going bad?

-Kevin
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Old 12-13-2013, 01:33 AM   #2
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Which cable provider do you have? I heard that FIOS is not compatible with booster amp.
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Old 12-13-2013, 06:22 AM   #3
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Which cable provider do you have? I heard that FIOS is not compatible with booster amp.
Comcast.

-Kevin
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Old 12-15-2013, 08:43 PM   #4
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Comcast.

-Kevin
My vote is that the Tivo is doing it. I am on OTA with a PCT distribution amp. When I disconnect and reconnect a cable and watch the signal level, it looks like the tivo is making adjustments over several seconds to see what signal level range it likes on that channel. When it enters a new range and makes the adjustment, the signal level jumps (usually higher).

When I had a Premiere, it couldn't handle the amped up signal. But some channels were too weak. My 1st solution was to use the distr amp but not plug its power cord in. My 2nd solution was to get a Roamio.

Edit: Also note, my amp only amplifies a little bit. But, I wish I would have gotten a unity gain amp. I don't need more signal, I just need the original signal level on 8 outputs.

Last edited by gfgray : 12-15-2013 at 08:50 PM.
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Old 01-03-2014, 10:04 PM   #5
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So a weird update on this......noticed tonight where ESPN was showing some slight pixelation. So I did my standard of tuning the channels where I see the lower signals and get pixelation when this happens: FOOD, A&E.

I tuned to those tonight and noticed they weren't in there normal 100 signal and 40-43 SNR.....they were down in the lower 90's dipping into the 80's.

So this time I tried restarting the Tivo to see whether that would help. Well it didn't. It fact, when it came back it was worse. A&E was almost completely locked up with signals into the 60-70's.

So again, I went down to the amp in the basement.....unplugged the coax going to that outlet, counted to 10, and plugged it back in. Sure enough, all signal levels on the Tivo back to 100 and all channels coming in perfectly.

Now I have two cable runs to that outlet.....tonight I decided to switch to the other run and I'll see how that goes.

But can anyone explain.....why over time does my Tivo see the signal levels drop.....this time I restarted and the levels dropped even more.....but every time I simply unplug and replug the line back in.....everything is fixed?!?

Could it be the cabling it self doing something over time? I tighten everything with a wrench, so I know the connection isn't getting loose.

Weirdest thing.

BTW - I now have a Roamio Basic in the bedroom, that is fed off the same amp, different output. I went and checked when my Plus started having issues and it was fine....signal levels normal.

-Kevin
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Old 01-03-2014, 10:12 PM   #6
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I see lower readings on my OTA Roamio sometimes but it is not correlated with pixelation or other signal flaws. I concluded that the Roamio shows lower signal levels while working fine.
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Old 01-03-2014, 10:27 PM   #7
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Lower readings for me typically mean pixelation.

I'm more hoping someone can explain why simply unplugging and replugging the coax from the amp causes the issue to go away. Is it the cable/amp or tivo? I'm leaning toward it's not the tivo since restarting it didn't fix the issue.

-Kevin
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Old 01-03-2014, 10:39 PM   #8
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It almost sounds to me like there's some sort of AGC (Automatic Gain Control) circuit in the TiVo and that's whacked out. That's a loop back circuit that's used to regulate the output of things like amplifiers. Maybe they use something similar on the internal amp of the Roamio plus/pro?

One thing I noticed when I had a Roamio basic here along with my pro is that the basic had significantly lower signal levels (80's vs high 90-100's), even when attached to the exact same line as the pro was. I'm thinking they use a completely different RF input stage for the plus/pro to compensate for the extra tuners.
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Old 01-03-2014, 11:04 PM   #9
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It almost sounds to me like there's some sort of AGC (Automatic Gain Control) circuit in the TiVo and that's whacked out. That's a loop back circuit that's used to regulate the output of things like amplifiers. Maybe they use something similar on the internal amp of the Roamio plus/pro?

One thing I noticed when I had a Roamio basic here along with my pro is that the basic had significantly lower signal levels (80's vs high 90-100's), even when attached to the exact same line as the pro was. I'm thinking they use a completely different RF input stage for the plus/pro to compensate for the extra tuners.
So do you think by unplugging the coax and plugging it back in again, that causes the tivo to readjust that AGC?

What I never did before was restart the tivo. I always unplugged the cable. So tonight I remembered to try restarting first. What really puzzled me was after the restart things were worse.

-Kevin
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Old 01-04-2014, 12:56 PM   #10
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So do you think by unplugging the coax and plugging it back in again, that causes the tivo to readjust that AGC?

What I never did before was restart the tivo. I always unplugged the cable. So tonight I remembered to try restarting first. What really puzzled me was after the restart things were worse.

-Kevin
Yes that's exactly what it's designed to do. In a nutshell, It's basically a tap off of the output that sends a signal back to the preamp stage to monitor the output level. If it goes low, it tells the amp to boost the output. If it goes high it does the inverse and drops the level.
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Old 01-04-2014, 11:33 PM   #11
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Yes that's exactly what it's designed to do. In a nutshell, It's basically a tap off of the output that sends a signal back to the preamp stage to monitor the output level. If it goes low, it tells the amp to boost the output. If it goes high it does the inverse and drops the level.
Dave,

Do you think maybe my amp is/was causing issues with the Tivo?

Reason I ask is tonight on both I was finding some weird signal levels. Now normally this 4 out amp only really has the 2 live outlets active....the other 2 go to empty drops.

The run to my Roamio Plus is usually with a signal of 100% and an SNR of 40-43.....this is amped. Yeah I know Tivo doesn't like those numbers but generally, I've never had a tuning issue and most of the time with 100% signal the picture is great.

The run to the upstairs Roamio Basic is usually with a signal around 90-95 and an SNR around 36-38.....this is also amped.

Tonight I decided to bypass the amp to test things. So now the main line into the house goes into a 3 way splitter:

-7dB - cable modem
-7dB - downstairs roamio plus
-3.5dB - upstairs roamio basic

The reason I put the basic on the 3.5dB out was it's a longer run....probably around 100ft.

So on the plus, those 100% and 40-43 SNR levels went down to what Tivo likes: 92-99% and 36-39SNR.

Ok, what's really weird is the upstairs basic either stayed the same or got better without the amp. So on A&E with the amp I was getting 90 signal.....without the amp I'm getting 92-95%. Most channels are 92-95% with 36-38 SNR.

Any ideas why the amp doesn't seems to effect the basic on the longer run? And do you think in the end it could be a bad amp or even the Tivo doesn't like to be fed from an amp? Could it have been the AGC in the Tivo that was acting whacky from the amp feed?


-Kevin
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Old 01-05-2014, 12:20 AM   #12
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Dave,

Do you think maybe my amp is/was causing issues with the Tivo?

Reason I ask is tonight on both I was finding some weird signal levels. Now normally this 4 out amp only really has the 2 live outlets active....the other 2 go to empty drops.

The run to my Roamio Plus is usually with a signal of 100% and an SNR of 40-43.....this is amped. Yeah I know Tivo doesn't like those numbers but generally, I've never had a tuning issue and most of the time with 100% signal the picture is great.

The run to the upstairs Roamio Basic is usually with a signal around 90-95 and an SNR around 36-38.....this is also amped.

Tonight I decided to bypass the amp to test things. So now the main line into the house goes into a 3 way splitter:

-7dB - cable modem
-7dB - downstairs roamio plus
-3.5dB - upstairs roamio basic

The reason I put the basic on the 3.5dB out was it's a longer run....probably around 100ft.

So on the plus, those 100% and 40-43 SNR levels went down to what Tivo likes: 92-99% and 36-39SNR.

Ok, what's really weird is the upstairs basic either stayed the same or got better without the amp. So on A&E with the amp I was getting 90 signal.....without the amp I'm getting 92-95%. Most channels are 92-95% with 36-38 SNR.

Any ideas why the amp doesn't seems to effect the basic on the longer run? And do you think in the end it could be a bad amp or even the Tivo doesn't like to be fed from an amp? Could it have been the AGC in the Tivo that was acting whacky from the amp feed?

-Kevin
Could be. What amp is it? Is it fixed or variable output? Some variable ones have the zero/null point at mid setting and increase when turned up and decrease (attenuate) when turned below midpoint.

What I was alluding to was maybe TiVo has a bad implementation of AGC. Maybe it's cascading the amps that's causing issues.

Does it seem like your issues are resolved by removing the amp and using the 3 output tap/splitter?
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Old 01-05-2014, 12:27 AM   #13
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Could be. What amp is it? Is it fixed or variable output? Some variable ones have the zero/null point at mid setting and increase when turned up and decrease (attenuate) when turned below midpoint.

What I was alluding to was maybe TiVo has a bad implementation of AGC. Maybe it's cascading the amps that's causing issues.

Does it seem like your issues are resolved by removing the amp and using the 3 output tap/splitter?
I think it's an Electroline EDA 2400. Each out is +7dB. No dials or settings for it, so I think it's fixed.

Hard to tell if issue solved as it didn't happen all the time. Will have to wait and see if levels stay consistent and I don't start seeing any weird level drops where pixelation is introduced.

Still can't fathom why without the amp to the basic on the longer run, the signal is same or better.

Thanks for taking the time.

-Kevin
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Old 01-05-2014, 12:41 AM   #14
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I think it's an Electroline EDA 2400. Each out is +7dB. No dials or settings for it, so I think it's fixed.

Hard to tell if issue solved as it didn't happen all the time. Will have to wait and see if levels stay consistent and I don't start seeing any weird level drops where pixelation is introduced.

Still can't fathom why without the amp to the basic on the longer run, the signal is same or better.

Thanks for taking the time.

-Kevin
Bad amp maybe? The TiVo Roamio could have an active RF input (similar to AGC) whereas if the signal is low on the input, it engages an amp to increase the levels. See how it responds over time with the splitter and the amp removed.
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