AVS Forum banner
Status
Not open for further replies.
1 - 13 of 13 Posts

·
Registered
Joined
·
113 Posts
Discussion Starter · #1 ·
Does anyone have any experience comparing the signal strength meters on various stb such as Toshiba, RCA, Dish, or Zenith to the Samsung bar graph? I have a Samsung sir t150 and am getting about 60% on the bar graph for my best signals. Others in my area are getting 90-100% on their meters, so my questions relates to comparing signal strenth on the Samsung verses other stb's.


Does 50% on Samsung bar graph equal 50% on another stb meter? Also does anyone know what is the minimum strength signal on the Samsung bar graph which will hold a signal?


Thanks, the Saint
 

·
Registered
Joined
·
532 Posts
That's a good question. I'm not sure what the Samsung uses, but I do know that if I adjust the potentiometer on my pre-amp up and down, it causes the signal strength bars to go up and down, too.


Maybe it's a combination of amplitude and digital information recovered?
 

·
Registered
Joined
·
983 Posts
The "Signal Level Indicator" on digital tuners isn't really a "Level" indicator as much as it is a 'Receivability" (or "Lack of Errors") indicator. You cna have a good 'signal level' and multipath will raise the 'error rate' lowering the readout. Since the various models use different chipsets the number displayed is pretty arbitrary from model to model. A '100' vs '80' may be a true signal level difference (caused by differences in sensitivity) or it may be slightly more multipath (leaves vs no leaves) that the system forward error correction is capable of masking.
 

·
Registered
LG 55" C9 OLED, Yamaha RX-A660, Monoprice 5.1.2 Speakers, WMC HTPC, TiVo Bolt, X1
Joined
·
45,759 Posts
Can't be done. As Lee explains, it's not really a strength meter and they all use different scales. If one were to have multiple DTV tuners and used the same input, you could in theory develop a conversion chart.


I think Peter Putman did something like this, check his web site: http://www.projectorexpert.com/
 

·
Registered
Joined
·
973 Posts
I have found that the DTC 100 gives a BER (bit error rate) reading which results in no errors or nearly no errors usually showing a reading of 94-100. Most signals will only give a 94 though. However under certain circumstances the station is broadcasting a clean enough signal (originating error free) that a 100 is possible.

Any signal giving a reading below 33 can not be recovered (over come erros) and be displayed.

In order to prevent dropouts reading must be above 38.

Plus no PSIP lock if below 28.

No ATSC pilot recognition below a 20.
 

·
Registered
Joined
·
113 Posts
Discussion Starter · #6 ·
Thanks for the quick replies. My original question was generated by my problems of multiple drop outs. I think that my main problem with drop outs is multipath and not signal strength. I currently am 25 miles from towers and am using a cm yagi 3023 with a cm 7775 preamp. My next step is to add a horizontal stack with a horizontal rotator and all needed parts are in the mail. Hopefully, this will solve my irritating drop outs; however, the signal is so spectacular that the quest for a stable image will be worth the effort.


the Saint
 

·
Registered
Joined
·
165 Posts
For what it's worth, a rotor solved my multipath problems. I was initially receiving signals on some channels that fluctuated on my signal strength meter between 100 and 12 at different times of the day. It seemed that even automotive traffic was causing multipath dropouts. Good luck.
 

·
Registered
Joined
·
463 Posts
Concerning the Samsung SIR-T150: I can get a good stable picture with the bargraph displaying one or two bars. At the same time, I can have pixelation and dropout with the signal at the halfway point (best I can get). That dropout and pixelation with strong power typically occurs with some signal fluctuations. I think the Samsung display is very different than the others. I wonder if Samsung scale starts at what is 30-40% for the other STBs
 

·
Registered
Joined
·
2,263 Posts
I asked this question to a CSR at the Samsung tech support line. After a ten minute wait she came back with a semi-understandable response about a signal measured in dB coming from the TV station and the display needing to be at least 50% to get a picture. She then explained that the LED on the front of the unit will be green if it gets a signal and red if not. I asked her if that meant that the strength indicator only represented the amplitude of the signal (since she talked about dB) and not the signal error rate. She said yes.


Given her lack of understanding of the question (her first answer was completely sensless) and her problems explaing the answer, I don't think she was completely up to track on what is going on.


I live 8 miles from the transmitters in Houston (think flat with no interference, direct line of sight) with an attic antenna but still only get 50 -60% signal strength on my SIR-T150 meter. My analog signals are just about perfect with minor ghosting on 2 of 8 channels. All of the transmitters are in the same antenna farm in the same direction from my house. There must be something else going on for me to get a 60% signal strength. Whatever the answer is it's not a big deal as I've never had signal problems.


-phil
 

·
Registered
Joined
·
532 Posts
Phil: that helps corroborate what I've seen when I adjust the potentiometer on my pre-amp. Increase the amplification, and more bars appear. Decrease it, and less bars appear.


But no bars appear unless it can assemble some kind of digital packet, it seems. If I rotate my antenna out of the particular path for a particular station, I'll get 7 bars, zero bars, 7 bars, zero bars, 7 bars, zero bars, and finally it'll stay zero bars when rotated completely away.


Turn down the amplifier, and it goes like this: 5, 0, 5, 0, 5, 0, and 0 to stay.


So, basically, I just rotate the antenna until I get a stable picture, and leave it alone.
 

·
Registered
Joined
·
1,525 Posts
If you are seeing a big difference in signal by tuning the amp, either the T150 is putting more emphasis on gain or you have a lot of loss in your feedline.


My tests with a Dish6000 show no difference in signal quality with or without a amp. This is because a amp can not create real gain like a good antenna, it only boosts what the antenna puts out and adds noise in the process. My current setup is no amp with low loss feedline.
 

·
Registered
Joined
·
113 Posts
Discussion Starter · #12 ·
The reason I got into this whole thing about signal strength is that I am experiencing the dreaded drop out for my digital signals. The signal meter on my samsung goes from 50% to zero and when I regain the signal it is again 50%.


I assume that the problem is multipath signals rather than signal strength. I started this thread only to compare signal strengths between various stb which are reported on my local thread.


Glenn has provided useful information and I have obtained the materials so that I can set up horizontal stack this weekend. Hopefully, this will solve my multipath problems and hence the drop outs. I also purchased a horizontal rotoator so that I can fine tune the antenna; however according to Glenn, the adjustments in the horizontal plane may not increase the signal strength on the meter but may result in a steady signal without dropouts and only trial and error will be the solution..


Dose anyone else have experience with this drop out problem, and are there any other suggestions?
 

·
Registered
Joined
·
411 Posts
CBGenrich needs to jump in here to explain his experience with the T150.


He has put together, for about $300, a portable antenna that works well with multipath (I think), and he makes it available to us Atlanta area folks to test our reception. He has experimented with an antenna antenuator and has confirmed that the T150 will display a good picture with only on bar displayed on the signal strength meter. Since I am less than 15 miles from the transmitters I have given up on an antenna preamp. (My RS DBT with connector soldered directly to the antenna works great sitting on top of my T150.)


We have lots of signal strength in the air. CB has rigged his car battery to allow him to drive around and check signal strength. With no intervening obstacles he has gotten reception (with a simple antenna) at more than 50 miles from the transmitters.


Tom
 
1 - 13 of 13 Posts
Status
Not open for further replies.
Top