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Quote:
Originally Posted by Theducksfan2010  /t/397256/sacramento-ca-ota/9930#post_24513176


I have very marginal signals, and splitting them 4 ways out if the preamp, I'm afraid will cost me dearly.


You think a distribution amp is the way to go? 2 three foot and 2 18 ft lines. Afraid just splitting a weak signal 4 ways will secretly degrade.

I can tell you what you need if I know your setup.


You're using the RCA preamp.


How long is the cable into the house?


Besides the power inserter, is there anything else between the end of the cable and the TV? Splitter, etc?


Chuck
 

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Quote:
Originally Posted by Calaveras  /t/397256/sacramento-ca-ota/9930#post_24513408


I can tell you what you need if I know your setup.


You're using the RCA preamp.


How long is the cable into the house?


Besides the power inserter, is there anything else between the end of the cable and the TV? Splitter, etc?


Chuck

The RCA preamp was needed to get any picture on KGMC with only a 25 ft Rg6 cable using the 91XG in this same location.


Setup: Colorstar C490 plugged into RCA preamp. Less than 50 ft of rg6 (probably 35-40) ran through the attic and ceiling


And behind the TV. I want to feed a 52" LCD tv, 32" TV, and two DVR's. One DVR has digital loop through, but I think the signal would be better split 4 ways than 3 and through a DVR to the TV.
 

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Quote:
Originally Posted by Theducksfan2010  /t/397256/sacramento-ca-ota/9930#post_24513471


The RCA preamp was needed to get any picture on KGMC with only a 25 ft Rg6 cable using the 91XG in this same location.

This tells you that KMGC is very weak and probably not 100% over time.

Quote:
Setup: Colorstar C490 plugged into RCA preamp. Less than 50 ft of rg6 (probably 35-40) ran through the attic and ceiling.


And behind the TV. I want to feed a 52" LCD tv, 32" TV, and two DVR's. One DVR has digital loop through, but I think the signal would be better split 4 ways than 3 and through a DVR to the TV.


I assumed the following: RCA preamp 24 dB gain and 2.6 dB noise figure, 50 feet of RG-6 going directly into one TV and TV noise figure of 6 dB.


Results for System Noise Figure at channel 51 (worst case):


No preamp, antenna directly to TV: 9.5 dB


Preamp to TV: 2.7 dB


Preamp to 4-way splitter to TV: 3.0 dB.



Assuming there's not something I don't know about, you can add a 4-way splitter with just 0.3 dB SNR loss. This will not be noticed in normal day to day operation. If you have a 4-way splitter or can easily obtain one, give it a try. You can always add a CM3410.



Notice that adding the preamp made nearly a 7 dB improvement to the system noise figure. That's why you saw such a big difference.


Chuck
 

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So you wouldn't use a powered distribution amp, even with signals near the digital cliff using the preamp??


Remember, I don't really have any "strong" signals, so I doubt I can overload any tuners.
 

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Quote:
Originally Posted by Theducksfan2010  /t/397256/sacramento-ca-ota/9930#post_24513638


So you wouldn't use a powered distribution amp, even with signals near the digital cliff using the preamp??


Based on the numbers from the components in your system that you gave me the math says you should not need one.


Below is a screen shot of a spreadsheet I made to determine System Noise Figure and Noise Margin. (Noise Margin is called Signal Margin on the spreadsheet.) In the blue cells I entered in the numbers for the components you gave me plus I added 1 dB for miscellaneous loss. No splitter is included.


Now let's add a 4-way splitter. The typical 4-way splitter has 7 dB loss. Look at the "Attenuator (dB)" column in the table and go down to 7. Go across to the "Signal Margin" column. With 7 dB of attenuation added after the preamp (i.e. a 4-way splitter) the Signal Margin is degraded just 0.3 dB. You'll never see that in day to day operation. Any signal that is so weak that 0.3 dB would make a difference will be too unstable to watch it. That might work in the lab but not in the real world.


The graph is just the data from the table plotted and gives you a quick look at the results. The long nearly flat range of the curve indicates excessive gain, about 10 dB worth.


The spreadsheet is available for anyone who would like to try it but I've always been met with silence when I've posted it in the past. I don't think anyone understands that you can engineer your system with it before you buy anything.

http://images.aa6g.org/System_NF.xls



Quote:
Remember, I don't really have any "strong" signals, so I doubt I can overload any tuners.


In most cases probably not. But excessive gain is not a good thing. It doesn't increase noise margin and it reduces the available dynamic range of the tuner. It's poor engineering.


Chuck
 

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Does anyone know how to get signal strentgh SNR DB using windows media center, or off of a computer that is using WMC for TV??
 

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Quote:
Originally Posted by Theducksfan2010  /t/397256/sacramento-ca-ota/9930#post_24516246

 

Does anyone know how to get signal strentgh SNR DB using windows media center, or off of a computer that is using WMC for TV??
I dont think so.... however, your tuner card might have the option with its proprietary software/utility. 
 

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I have never done any TV on a computer, my card is: ViXS PureTV-U 48B0 (NTSC/ATSC Combo)
 

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Not only is the distribution amp unnecessary, but fine tuning the antenna, to get picture on one TV and none on the other, pulling it out and putting the passive 4 way splitter in, the channel was watchable on BOTH TV's. The distribution amp cost me, severely. Love running the tests, but glad to get my money back.


Ty @Calaveras
 

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I don't know if it's the best way to wire things, but this seems to work well for me. Seeing I'm so close to Sutro Tower I can't use a pre-amp. Adding one just overloads the tuner.


I take the output of the coax cables from my four antennas, connect them to a 4 4-output distribution amps (Rocketfish RF-G 1179) and then connect short coax runs to the switches for TV, DVR, Converter Box and HD Home Run. I lose little to no signal with the distribution amps and switches, so I get about the same signal at each devise as I would connecting the coax to it directly.


Here's a link to my web page about my TV antennas: http://www.larrykenney.com/tvantennas.html


Larry
 

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Quote:
Originally Posted by Theducksfan2010  /t/397256/sacramento-ca-ota/9870#post_24492295

Updating my scorecard


My records show you have received every channel from 2 through 51.....(At one time or another)
Except..... no digital reception on .......2, 4,5, 6, and 12


Looks like no dedicated mobile radio service channels in the valley....... As 15 through 18 are reserved for such services here coastside.
 

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Quote:
Originally Posted by 888CALLFCC  /t/397256/sacramento-ca-ota/9930#post_24517189



Updating my scorecard


My records show you have received every channel from 2 through 51.....(At one time or another)
Except..... no digital reception on .......2, 4,5, 6, and 12
Absolutely correct, unless you are counting reception on 16, & 27 that was analog, so no digital reception on them also.

 

I have some work ahead of me this summer during the inversions......
 

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We snapped something inside the preamp when we did the install, it moved and turned. Replaced the preamp today, and forgot the electrical tape on the rotor. Is it ok with the cable running straight from the antenna into the preamp, without being taped down in between?
 

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Quote:
Originally Posted by Theducksfan2010  /t/397256/sacramento-ca-ota/9930#post_24520590



We snapped something inside the preamp when we did the install, it moved and turned. Replaced the preamp today, and forgot the electrical tape on the rotor. Is it ok with the cable running straight from the antenna into the preamp, without being taped down in between?


Depends on how secure the F connector is on the cable. I've had cable pull out of the connector just from the wind moving the cable.


Chuck
 

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The F connector was stuck on the preamp so hard, I had to use pliers to get it off (DirecTv RG6) and the f connector ripped off. So I had to cut the cable and put a new one on. All I had laying around was a twist on, put it on really well and crimped it good. Should hold up well. Just wish I had taped it back to the mast.


Was not fun replacing a F connector on the roof.


Would you leave it the way it is @Calaveras or take the whole thing down, tape it to the mast, and put it back up?

Oh, I got a passive 4 way splitter like you suggested, worked so much better than the RCA powered distribution amp. (The distro amp was degrading signals).
 

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Just did a complete tv install for the mother in-law in Thornton . When she isn't watching tv, she didn't want to be able to see any part of it. Probably 8 miles from the Walnut Grove Towers, 3 miles east of 5 right across from them. Don't want to overload the tuner, but needed a amp four the few Bay area stations that come in (14, 36, 42, and 54). Used a RCA amplified antenna and a first gen converter box. 41 channels received.




You can see the antenna and converter box inside the cabinet on opposite sides of the tv. My real question is, every time the box goes to KQED 54.1 the box gets the black screen of death, code runs and it shuts off. Had to delete the channel. Is it something inside the signal that is doing this, should I notify KQED, or is it because it's an older converter box 2010ish, I think?
 
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Just helped a friend of mine install an HD8200u in his attic in Yuba City.  He is pointed toward the south, has about 150 of coaxial (had to run in outside and under the foundation), and is only getting 21 channels (no ABC, no PBS).  Any suggestions besides a preamp?  He is pointed at 180 degrees.  PBS/ABC are at 174 degrees (cant move antenna anymore, its huge and his attic is not huge).  

 

Anyhow, it was a fun project.  Fortunately his attic was old school (partially finished).  
 

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Quote:
Originally Posted by jhughy2010  /t/397256/sacramento-ca-ota/9930#post_24521639


Just helped a friend of mine install an HD8200u in his attic in Yuba City.  He is pointed toward the south, has about 150 of coaxial (had to run in outside and under the foundation), and is only getting 21 channels (no ABC, no PBS).  Any suggestions besides a preamp?  He is pointed at 180 degrees.  PBS/ABC are at 174 degrees (cant move antenna anymore, its huge and his attic is not huge).  


Anyhow, it was a fun project.  Fortunately his attic was old school (partially finished).  

Preamp
You ABSOLUTELY need a preamp! especially with 150ft of coax!!!!


Another possible need for a preamplifier will be on installations with long coaxial cable runs from the antenna to the TV set. If there is 50 feet or more of cable between the antenna and TV set, a preamplifier may provide an improvement. http://support.channelmaster.com/hc/en-us/articles/200383665-Do-I-need-a-preamplifier-for-my-antenna-
 

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Ducksfan... Is the coax on your antenna shown in the picture wrapped through the elements? Can't tell for sure from the picture, but it looks suspicious. If so, it could influence your reception... in a bad way.


Larry
 

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 @Larry Kenney it's hanging (with rubber gasket to prevent water) from the connectors down, behind the last UHF element. Is that bad? Do I need to add a drip loop and run it along the bottom boom to the mast and down, leaving enough play for rotation?
 
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