811 OTA 81% then drops to 49%??????

[Iceman]

I just don't understand it. I get signals with an amplifier on my antenna up to 81%. Then it suddenly goes down to 49% and I lose all signal. What the hello is going on? I have tried different cables from amplifier to receiver, 59U and RG6 with no difference in outcome. I have tried amp and no amp, also with no difference other than my signal only goes to 68% with no amp.
I have a feeling that the software bug has not been fixed yet. Any suggestions?

 

[Carl B]

You suffer from multi-path problems and/or seasonal change problems. Is your antenna pointed directly at the source of the channel that is dropping out? If not, point it that way. Should take care of multi-path.

If you still have a problem, you probably don't have a LOS to the source and you are picking up a bounced signal or several bounced signals. When the trees leaf-out and the wind blows, the path of those bounced signals is constantly interfered with. In that case you need a better antenna or a better antenna location.

It is unlikely that what you are experiencing is an 811 issue. Some other OTA STBs may catch and hold your bouncing signal better than the 811, but the 811 is likely doing the best it can with a poor signal situation.

 

[snathanb]

It is unlikely that what you are experiencing is an 811 issue. Some other OTA STBs may catch and hold your bouncing signal better than the 811

I did a little light reading into multipath. When the FCC was deciding on the standard they also considered COFDM modulation, which offers much better resistance to multipath compared to 8VSB, however didn't offer the same range.

Here are the conclusions that were reached:

"The results of the field testing of 8VSB and COFDM at the specified data rates indicate that 8VSB should be suitable for a broadcast service when a 30 foot outdoor antenna is used for reception.


The results of the field testing of 8VSB and COFDM for outdoor reception using a simple antenna at 6 feet are far less optimistic that the reliability of service for that reception configuration will be adequate for defining a broadcast service with either system tested.

The results of the field testing of 8VSB and COFDM indicate that although some viewers would be able to enjoy indoor reception with either system, neither system exhibited the level of reliability that would be required of a practical broadcast service based solely on service to indoor antennas. "


For the complete description and conditions of the tests, check out:

http://web-star.com/hdtv/mstvtestsum.html

 

[Pb ft.]

Some people think that the "49% problem" is an 811 issue some think it's an antenna/multi-path issue. IMO it's an 811 problem. Improving my antenna didn't help. Here is how I tried to solve the 49% problem. It didn't help.

 

[GaryPen]

Some people think that the "49% problem" is an 811 issue some think it's an antenna/multi-path issue. IMO it's an 811 problem. Improving my antenna didn't help. Here is how I tried to solve the 49% problem. It didn't help.

It's actually both. But, as it is the 811's apparent difficulty with multipath rejection that is the problem, it puts the onus on the 811. Most other brands/models of OTA HD receivers do not have that issue, and will probably receive most or all of your "49%" channels.

Another thing that points to it being an 811 issue is that OTA reception has improved and/or degraded immediately following various sw updates.

 

[welshboy]

I have two 811's, one started the 49% problem after the 266 upgrade. I use the same antenna for both 811's. I swopped the inputs and could then prove to Dish that it was a 811 problem not the antenna. They sent me a refurb. unit. Installed and the problem went away.

 

[GaryPen]

Could that mean that it is a HW, not SW, issue? Hmmm.

 

[SimpleSimon]

Could that mean that it is a HW, not SW, issue? Hmmm.

For that specific case, sure - HW. However, in general, I think there's definitely some software garbage going on. My speculation is that they're messing with the selectivity, sensitivity, and other tuner settings.

 

[rjruby]

Definitely an 811 issue

Whether it's hardware or software, it definitely appears to be an 811 issue.

I just installed an 811 last weekend, software rev 266, and have the same dreaded 49% problem.

The 811 is fed from the same source as my Dish 6000 and Samsung SIR-T165 that are able to lock-on rock-solid to the same signals.

Bob

 

[snathanb]

For that specific case, sure - HW. However, in general, I think there's definitely some software garbage going on. My speculation is that they're messing with the selectivity, sensitivity, and other tuner settings.

I agree... increase the sensitivity and you probably get more multipath problems. Decrease the sensitivity and you get customers who once had signal no longer getting it...

 

[mike123abc]

As I have mentioned in other posts I was able to remove the 49% problem by working on my antenna. The problem a lot of people face though is that channels are in multiple directions and fixing one by moving the antenna breaks another one.

One thing I also have had to play with in the past is signal attenuators. IF it is a strong station giving you the problem, perhaps putting a small attenuator on the line at the 811 would solve your problem (i.e. knock down the signal strength to where the ghost is not causing problem).

 

[GaryPen]

Mike - But, you must still remember that all this additional work for good OTA reception on the 811 is unnecessary with other receivers. Bob's post above is quite typical.
All of this extra aiming of the antenna, and use of attenuators or amplifiers is simply another workaround to another 811 bug. Luckily for me, it isn't affecting me too badly right now. But, I have the advantage of being able to mount my antenna approx. 40 ft above street level.

 

[cabledave]

Attenuators

One thing I also have had to play with in the past is signal attenuators.

I have found with my 49% problem on one of my 811s (have 3) that a 10db attenuator corrected the lock problem that I was having on 2 channels.

Overloading the 'front end' of digital receivers is fairly common. Motorola digital cable boxes start to pixilate when you feed them signals higher than +10 to +15db. They actually work best at -10 to 0db.

I have a Zenith STB that actually came with a 10db attenuator to correct any overload issue. I don't take all of the blame away from the 811, as it seems completely unable to deal with even moderate multi-path.

 

[Carl B]

There are presumably better OTA STBs, but they cost $400+, don't integrate into your EPG, and don't also serve as a DBS receiver. In addition, if you search other Internet forums you will also find there are other chronic problems with many of these OTA STBs, particularly some of the Sammys.

OTA DTV is in its infancy and there are still many technical solutions to be found. The 811 is perfert, but for the money, it is quite satisfactory.

I'm in a DTV wasteland, metro-Denver, and I've improved my 811 reception w/ each antenna system upgrade I've made. I don't have LOS to any broadcasters and half my stations are 90 degrees from the other half. I get 5 of 7 available stations. One extremely low power station I point at, that hardly anyone beyond downtown Denver gets, I get the 49% reading on. Most others in my area get zero. My other 49% is at 90 degrees from my aim and is high power. I got it before the trees leafed out or, if you want to blame E*, before P266. But, now it is 49%. However, on real windy days, I can still lock the signal. Surely the 811 should have been designed to deal with the trees and the wind!

I bought a better antenna, but broke my shoulder before I could install it. Can't get back to the issue until July 4th, but then I'll take care of the other 2 stations.

 

[rjruby]

I have found with my 49% problem on one of my 811s (have 3) that a 10db attenuator corrected the lock problem that I was having on 2 channels.

Based on cabledave's experience, I installed a variable 20 db attenuator from Radio Shack:
http://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=15-678

By varying the attenuation, it corrected three of the four stations I was having problems with.

This does require that I have to adjust the attenuation occasionally since reducing the level does affect other stations that were working.

Bob

 

[smodak]

Based on cabledave's experience, I installed a variable 20 db attenuator from Radio Shack:
http://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=15-678

By varying the attenuation, it corrected three of the four stations I was having problems with.

This does require that I have to adjust the attenuation occasionally since reducing the level does affect other stations that were working.

Bob

Great Info! Can you please write in detail(I am a newbie), what you did. I want to try that.
Thanks

 

[rjruby]

Great Info! Can you please write in detail(I am a newbie), what you did. I want to try that.
Thanks

I just attached the input of the attenuator to my antenna and the output of the attenuator to the 811 and then adjusted the attenuation until the signal locked.

 

[smodak]

I just attached the input of the attenuator to my antenna and the output of the attenuator to the 811 and then adjusted the attenuation until the signal locked.

But did you have to do it for all the channels individually or just one channel? Everytime you change the channel, do you have to adjust the attenuation? What attenuator did you use?
Thanks a lot!

 

[WeeJavaDude]

But did you have to do it for all the channels individually or just one channel? Everytime you change the channel, do you have to adjust the attenuation? What attenuator did you use?
Thanks a lot!

I knew my most proplematic station and I tuned for that one and then checked the others. In my case, I don't have to adjust it at all. It was set once and I I have not had any problems with my signal. I got my attenuator from Radio Shack.

 

[Iceman]

reply

Based on cabledave's experience, I installed a variable 20 db attenuator from Radio Shack:
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=15-678

By varying the attenuation, it corrected three of the four stations I was having problems with.

This does require that I have to adjust the attenuation occasionally since reducing the level does affect other stations that were working.

Bob

Attenuator is designed to reduced your signal strength to prevent ghosting, etc. caused by signal overload, right?
This isn't going to help anyone who lives in the sticks.