# Improving Roamio OTA Reception - Strength, SNR, RS Uncorrected



## Ronj007 (Jan 3, 2016)

I have a Tivo Roamio (OTA & Cable model) unit and I just switched from Cable to OTA transmission. Overall I'm impressed with OTA offerings. That said, I have a few channels that I need to improve. It's not that they don't come in, they do for long periods of time and then show some pixelation. I've aimed the antenna with slight adjustments and improved the signal strength that way the best I can...but I have some questions about some of the posts Ive seen across the net. BTW, I peg out on 72% like most folks are saying is the maximum signal. I wish Tivo would fix this so that it would go 0 - 100%! Their support staff act like there's something wrong with your setup when you call in.

*Attenuator*
I saw a post about installing an inline attenuator to improve reception. I'm trying that, my first attempt was with a -12dB attenuator and I'm very confused by my results. First, it's obviously too much because now a few of my channels are below the threshold and Tivo won't show them. However, to my surprise, although every channel that dropped down at all, dropped down into the 40's, but the signal is far more stable. What I mean by that is that the strength reading and the peak strength meeting are now usually the same and I get absolutely no pixelation. On the same channel without the attenuator I'm getting somewhere in the 50's but the signal flips around and eventually drops down and I get pixelation. When I do get pixelation, I start to get RS Uncorrected errors and my SNR drops to around 15. Interestingly, with the attenuator in place, the signal is at 40-42% and my SNR is at 16-17db.

So my questions are, what in the world is going on? Why does the attenuator stabilize the signal? Why is the Roamio pixelating on a channel with a higher but varying signal, but not pixelating on a channel with a lower more stable signal? Can someone point me to an explanation for RS Uncorrected/Corrected?

I have a 3db and 6db attenuator on the way that I'll try next.

Any suggestions on what I should do to get the best outcome would be appreciated!


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## JoeKustra (Dec 7, 2012)

RS: https://en.wikipedia.org/wiki/Reed–Solomon_error_correction

For everything else, sorry.


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## NoNose (Nov 27, 2015)

Ronj007 said:


> I have a 3db and 6db attenuator on the way that I'll try next.
> 
> Any suggestions on what I should do to get the best outcome would be appreciated!


So, here's what a commercial antenna installer told me:

*An attenuator lowers amplitude of an OTA signal.* It is best used if you are close to a signal source that may be overloading your tuner(s), and therefore causing the quality of the signal to vary.

*An amplifier raises the amplitude of a distant signal.* Note however, an amplifier may also raise unrelated/unwelcome video noise right along with the target signal.

Back in the day of analog tv transmission, you could get away with some twiddling of the signal amplitude. However, a digital signal does not respond the same way. As much as professional installers would love to sell you a product off the shelf, they also realize that if they do recommend something, you are very likely to be disappointed. That's not good for their business.


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## Ronj007 (Jan 3, 2016)

Thanks. The signals in question were only in the 50's before adding the attenuators, so I don't think they were maxing out. I'm wondering why the roamio tuners detect the signal as more stable with thenattenuator attached. Does the attenuator act as a signal filter too...effectively filtering out noise?


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## Nickipedia (Jul 18, 2015)

This sounds like a multipath problem. The signal propagation from certain broadcast towers are causing your pixelation. You may want to try a variable attenuator like this: https://www.antennasdirect.com/store/Variable-Attenuator.html

Multipath can be a big problem in areas where you're close to one tower and farther away from others much farther from the others (like most minor cities.) What is your zip code? That would help diagnose if you have a signal that is too strong and is causing these problems.

The variable attenuator will help you find the sweet spot to keep your SNR high enough to minimize uncorrected errors on most channels, while letting you bring down the signal on your problem channel. If this doesn't work you may need a frequency specific attenuator for the channel or channels that are causing the problem.


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## Ronj007 (Jan 3, 2016)

94041

Channels are 5-1 & 4-1. These come from Sutro tower in San Francisco according to:

http://www.choisser.com/sfonair.html


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## Nickipedia (Jul 18, 2015)

This chart from tvfool might help you:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=51343ba59c26b3

Also take a look at the stations and their power on this map. Just type in your address:

http://www.tvfool.com/index.php?option=com_wrapper&Itemid=90

In your area a variable attenuator should help given your signal levels. You'll have to play with amount of attenuation once it's installed to find a good level.


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## ClearToLand (Jul 10, 2001)

NoNose said:


> So, here's what a commercial antenna installer told me:
> 
> ...*An amplifier raises the amplitude of a distant signal.* Note however, an amplifier may also raise unrelated/unwelcome video noise right along with the target signal...


I always have a problem when I read this type of statement (bold quote).

An amplifier DOES NOT raise the amplitude of a distant signal. If the signal is not present at the antenna, or at the insertion point of the amplifier, no amount of amplification is going to magically pull it out of the muck. What an amplifier will do is compensate for the losses (cables, splitters, connectors) between the amplifier and the receiving device(s).

My advice to someone considering the purchase of an amplifier is to first temporarily setup a TV (back in the NTSC analog days I had a 12" Zenith Black and White that was easy to carry around; now I have a 19" Sylvania LCD for ATSC digital) at the point where you intend to install the amplifier. If the TV gets all the channels you desire at the quality you desire, than an amplifier of the appropriate gain to negate the losses will solve the problem. If the TV doesn't work properly you need to investigate / troubleshoot the problem. You may need to turn the antenna, raise the antenna, lower the antenna, move the antenna horizontally, replace the antenna with one with a higher gain. Once you have a good signal feeding one TV close to the antenna, you can determine how much amplification you need.


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## ClearToLand (Jul 10, 2001)

Ronj007 said:


> ...*Any suggestions on what I should do to get the best outcome* would be appreciated!





Nickipedia said:


> *This sounds like a multipath problem*. The signal propagation from certain broadcast towers are causing your pixelation...
> 
> ...The variable attenuator will help you find the sweet spot to keep your SNR high enough to minimize uncorrected errors on most channels, while letting you bring down the signal on your problem channel. *If this doesn't work you may need a frequency specific attenuator for the channel or channels that are causing the problem*.


@Ronj007,

What type of antenna do you have (Make & Model) and where is it located / what direction is it aimed / how high is it AGL?

From the first TV Fool LINK graciously posted by @Nickipedia, IANAE, but possibly KICU-TV(36) @ 13.4 miles may be interfering with KRON-TV(38) @ 32.8 miles. I'd read:
*TV Fool / Signal Analysis FAQ: What are co-channel and adjacent channel warnings?*​
and I'd SCAN / SEARCH through:
*AVS Forum / Local HDTV Info and Reception: San Francisco, CA - OTA*​
to see if anyone else in your area (San Francisco, CA) is experiencing a similar problem.

Depending on the 'lobes' of your current antenna, if it's now aimed at ~320 degrees for KRON-TV, KICU-TV is ~120 degrees clockwise at ~60 degrees. If you rotate your antenna to 350 degrees you might still get enough of KRON-TV and reject more of KICU-TV since it will now be directly 90 degrees off your aim point where reception should be at a minimum (i.e. you're lowering the signal strength of KICU-TV *WITHOUT* using an attenuator which would lower the signal strength of ALL of your channels).

Just thinking out loud - again, IANAE, so you'll need to read the AVS Forum LINK and do some GOOGLE'ng but @Nickipedia may be onto something.

Good Luck!


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## Ronj007 (Jan 3, 2016)

Thanks everyone for the help and especially for the calculations.

My Antenna: http://www.amazon.com/dp/B00WW7H9ZI/ref=sr_ph?ie=UTF8&qid=1452395881&sr=1&keywords=1byone

I've been up on my roof more times than I care to think about anymore...but this last trip was interesting. Using my iPhone compass I once again looked at the angles from the TVfool.com report... 316 degrees - 55 degrees. I moved my antenna up and over and the strength meter readout on my Tivo now registers 72 (the highest reading for OTA according to some) for what was the most troublesome channels, other channels dropped down but they come in clear. The only real challenge now is with NBC (11.1, 11.2, and 11.3)! Interestingly, it seems 11.3 (KSTSDT3) is a duplicate of 11.1 (KNTVDT) although I can't seem to find much information on that. All three of these channels come from Mt San Bruno but 11.3 registers 5% more signal than 11.1 and it isn't pixelating whereas 11.1 is... I'm going to try it like this for a while and see if this positioning and using 11.3 instead of 11.1 will do the trick.


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## ClearToLand (Jul 10, 2001)

Ronj007 said:


> ...Using my iPhone compass *I once again looked at the angles from the TVfool.com report... 316 degrees - 55 degrees. I moved my antenna up and over and the strength meter readout on my Tivo now registers 72* (the highest reading for OTA according to some) for what was the most troublesome channels, other channels dropped down but they come in clear...


So, in what direction, in degrees, is your antenna currently aimed?

Did you try ~350 degrees like I suggested?

*EDIT:* EEKK! 



Ronj007 said:


> ...My Antenna: http://www.amazon.com/dp/B00WW7H9ZI/ref=sr_ph?ie=UTF8&qid=1452395881&sr=1&keywords=1byone
> 
> *1byone® Omni-directional Amplified Outdoor Antenna* (_receiving signals from or transmitting in *all directions*_)​


Sadly, you cannot aim this antenna; it has no 'lobes'. It receives equally from all directions. 

Hang on - let me find you the LINK to build a UHF Bow-Tie antenna *CHEAP* to test with...

*EDIT 2:* *AVS Forum / HDTV Technical > How to build a UHF antenna...*

You could try temporarily taping some aluminum foil on the side of your antenna pointing to 55 degrees to block some of the KICU-TV signal. Otherwise, you'll either need to buy a DIRECTIONAL antenna since KICU-TV is so close in both mileage to your home and in frequency to KRON-TV - 36 vs 38...

Or you'll need to GOOGLE 'Notch Filter' (_a filter that attenuates signals within a very narrow band of frequencies_), IIRC; an attenuator tuned to reduce the signal ONLY for channel 36.

Looking forward to reading what @Nickipedia has to say about your antenna / situation.


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## Ronj007 (Jan 3, 2016)

I guess I'm not sure how to aim it since its omnidirectional. It's mounted so that signals from 270 to 90 should hit it.


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## ClearToLand (Jul 10, 2001)

Ronj007 said:


> I guess I'm not sure how to aim it since its omnidirectional. It's mounted so that signals from 270 to 90 should hit it.


I updated / edited Post 11...


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## Ronj007 (Jan 3, 2016)

Thanks for the updated instruction...I've never thought about a notch filter. That said, with the last adjustment I described, everything is coming in without pixelation. That includes KRON and KICU too. The only concession I'm making is that instead of 11.1 (KNTV) I'm using 11.3 (KSTS) but it looks like they're the same anyway. If I see any pixelation in the next few days I'll try what you've written in #11. Thanks again!


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## Ronj007 (Jan 3, 2016)

Btw, 11.1 KNTV is frequency 12 whereas 11.3 KSTS is frequency 49. Both are broadcast from the same location. Maybe the higher frequency has something to do with the better reception?


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## JoeKustra (Dec 7, 2012)

Ronj007 said:


> Btw, 11.1 KNTV is frequency 12 whereas 11.3 KSTS is frequency 49. Both are broadcast from the same location. Maybe the higher frequency has something to do with the better reception?


Perhaps since KSTS is twice the power and height compared to KNTV is a factor.
https://en.wikipedia.org/wiki/KNTV

https://en.wikipedia.org/wiki/KSTS


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## Ronj007 (Jan 3, 2016)

Maybe, but that would mean that KSTS would be broadcasting 11.3 from the higher transmitter along with its other stations 48.1 & 48.2, while 11.1 & 11.2 would come from the lower transmitter. 

That's possible but is it likely?


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## JoeKustra (Dec 7, 2012)

Ronj007 said:


> Maybe, but that would mean that KSTS would be broadcasting 11.3 from the higher transmitter along with its other stations 48.1 & 48.2, while 11.1 & 11.2 would come from the lower transmitter.
> 
> That's possible but is it likely?


Just speculating here. The antenna specs seem to favor UHF. VHF, even high band, would be happier with a larger antenna.

The specs for UHF say 470MHz to 862MHz, which is logical. But the VHF specs indicate 87MHz to 230MHz, which doesn't make sense to me. Perhaps that's a European band?
https://en.wikipedia.org/wiki/North_American_television_frequencies#Broadcast_television


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## HairyHarry (Jan 24, 2020)

Albeit it this is an old thread, but the following information helped me with a similar situation:

*Problem:* if your multi-tuner TiVo is splitting-up your antenna signal so much that you can’t receive any or many TV channels, which is the problem I had with my 4 tuner Roamio-OTA, then I found a solution that works great in my location.

*Solution Attempt 1:* at first I spoke with the TiVo repair experts at weaknees.com and asked them if they could take out or otherwise cap-off 2 or 3 of my Roamio’s 4 tuners and thereby leave all or most of the antenna signal for the remaining tuner(s), but their technician said it wasn’t possible, although they said the old two-tuner Tivo Premier model does not have that problem. Also, I’ve read that the 6 tuner TiVo Roamio-OTA has a menu option to shut off some of its tuners.

I then tried the other logical solution of purchasing a pre-amplifier to boost the antenna’s signal and that worked great, but NOT well at all in the beginning. I started with an inexpensive antenna pre-amp purchased on eBay for around $20 and that helped boost just a few channels enough to tune them in reliably, but I should add here that my antenna is a ClearStream 2MAX UHF-VHF Indoor-Outdoor HDTV Antenna placed inside a ground floor apartment within a four story brick building.

Receiving a few channels is about 40 channels short of what my antenna-based TV can easily receive & display here when the antenna circumvents my TiVo Roamio-OTA and is hooked-up directly to the TV, so this first attempt was not a good solution.

*Solution Attempt 2:* then I moved from a suburb to lakeside downtown Milwaukee into the same size brick building and again on the ground floor. This address is five miles closer to the local TV broadcast towers, which are now only 7 miles away, but this address has two very tall buildings around it that might be blocking reception a little.

The result was that the Tivo will only display one channel here with the $20 pre-amp, while the TV with the antenna hooked-up directly to it (with the TiVo circumvented) receives & displays all 40+ local channels clearly & reliably.

Then I found two helpful pre-amp facts:

(1) an antenna needs a pre-amp to boost its signal when, of course, it has a low signal (as in my case) or if it is at one end of a long cable (i.e., a rooftop antenna 40 feet away from the TV). This is because cable length decreases signal strength as cable length increases...

(1.1) ...AND though this doesn’t apply to my indoor situation, it’s also very important for antennas with long cables to have the pre-amp located within a few feet of the antenna itself so that the pre-amp receives & amplifies a clear signal directly from the antenna before the signal is diminished by traveling along many feet of cable to the TV. BTW, the recommended pre-amp (see below) includes this capability, which is enabled by its power injection feature.

(2) an antenna signal pre-amp is most effective when it includes a good low-noise filter;

*The Successful Solution*: ...and then I found the *Channel Master Model #1 pre-amp for $65*. It has two signal boost levels: 18db & 30 db along with a good low-noise filter (and I believe it has an LTE filter too for preventing any local cell phone signal from crossing-over into any incoming local TV broadcast signal). BTW, Channel Master will accept a return for any reason for refund (I believe if returned within 30 days) if their amp doesn’t work for you.

I set up the Channel Master with the TiVo and found that its 18db setting clearly & reliably receives all the local channels (i.e., 4.1, 4.2, 4.3...6.1, 6.2 etc. etc.), about 48 channels including all the major broadcast channels.

BTW, 30db is recommended for antennas placed at much longer distances from local TV broadcast towers (I’ve read 50+ miles). Here though, 30db is clearly too much signal (over-generation) and that results in zero picture & audio.

Yet, as mentioned above, 18db successfully boosts the signal to the TiVo on all the channels here and registers each channel at about 52 on the TiVo’s internal signal meter (44 seems to be about the minimum meter reading here for a broadcast TV channel to display a clear picture).

This problem had me thinking I was going to have to find a better DVR. I hope this helps others with this TiVo signal strength problem.


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