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Old 10-Oct-2015, 5:41 AM   #1
scott784
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Join Date: Dec 2010
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Help me understand signal loss when using a splitter

When using an antenna with a splitter, it was my understanding that even one split caused a 50 percent drop signal strength coming down to two individual televisions. That has always sounded significant to me and a driving force to stop me from ever considering a single antenna for multiple televisions.

But then I hear more recently that it doesn't really work like that. I read recently that it's only something like 3.4 db for each split. And in reality, a single split (using a single antenna) is really minimal loss. So now I am just trying to wrap my head around it and get an understanding of what the true reality is.

Recently, I have ordered an Antennas Direct DB8 which I intend to install in my attic and start out by only running the line down to a single television. But ideally, I think it would be great if I could tie the antenna into my cable box whereby allowing me instant antenna access at each outlet for my 3 televisions.

However, I am never going to entertain this idea unless I can get some idea that the signal loss is truly very minimal (at least with using a booster). Can someone shed some light on this topic for someone that doesn't fully understand the amount of degradation that takes place with each split?

For example, let's say I've got a tv currently getting an average of 85 percent signal strength from a given network station. If the antenna wire feeding that television is then split one time in order for the antenna to service two televisions, what would be a realistic signal strength drop? And if a booster is introduced at the cable box, are some for more effective than others in terms of mitigating this drop in signal?

Many thanks to someone who can share their insight to enable me to get a better understanding of any consequences of doing a split, even if it's just for two televisions.
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Old 10-Oct-2015, 11:04 AM   #2
ADTech
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You have to first wrap your head around the logarithmic decibel scale and leave percentages behind. (http://www.hdtvprimer.com/ANTENNAS/g....html#decibels) Also, do NOT confuse the "percentage" displayed on the "signal meter" with the prior. Ignore the number on the TV set screen until it gets to your dropout number, whatever it happens to be for that particular set.

Under lab conditions, the dynamic range of digital tuners is about 80 dB, that's a difference of 100,000,000 times signal power between the weakest and the strongest usable signals. You can see that you can cut that signal in half (3 dB, 50%) numerous times (almost 27) before running out of signal power.

Use a figure of 4 dB insertion loss for a two-way split for planning. Most of the splitters I've tested come in somewhere between 3.3 and 4.5 dB per port.

100' of RG6 and a balanced 3-port splitter will total about 10 dB of insertion loss, worst case. As long as your available signal power at the antenna plus the gain of the antenna exceed this margin, then there's plenty of signal to go around.

Quote:
For example, let's say I've got a tv currently getting an average of 85 percent signal strength from a given network station. If the antenna wire feeding that television is then split one time in order for the antenna to service two televisions, what would be a realistic signal strength drop?
Impossible to predict since the displayed "percentage" has no known correlation to anything we know about. What is important is determining where it drops out, then staying above that with some margin.

Quote:
the amount of degradation that takes place with each split?
It's not "degradation", it's attenuation. Degradation implies that distortion or damage has taken place but it hasn't, the signal is simply weaker.
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Last edited by ADTech; 10-Oct-2015 at 11:08 AM.
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Old 10-Oct-2015, 5:17 PM   #3
rabbit73
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Quote:
But ideally, I think it would be great if I could tie the antenna into my cable box whereby allowing me instant antenna access at each outlet for my 3 televisions.
Cable and OTA signals must not be combined in the same coax. There is the possibility that cable signals might be radiated by the antenna system, which the FCC frowns on because it might create interference to other services, like aircraft control.

The best way to do it is to have OTA signals go into the antenna input of the TV and have the signals from the cable box go into an aux input of the TV
Quote:
Recently, I have ordered an Antennas Direct DB8 which I intend to install in my attic and start out by only running the line down to a single television.
What do you think the DB8 (the new version is DB8e) will do for you that the C4 didn't?

Your previous thread:
Antennas Direct ClearStream 4
Quote:
Originally Posted by scott784 View Post
Yesterday, I installed an attic mount Antennas Direct ClearStream 4.
Quote:
However, I am never going to entertain this idea unless I can get some idea that the signal loss is truly very minimal (at least with using a booster). Can someone shed some light on this topic for someone that doesn't fully understand the amount of degradation that takes place with each split?
The signal loss can be minimal if your equipment is connected in the proper order and the antenna is aimed directly at the transmitter. The DB8 is a very directional antenna. What azimuth will be used for the aim? What channels do you expect to get?

I looked for your tvfool report in your previous threads, but it is no longer on the server. As close as I could get was "I live in the 27104 zip code (west side of Winston)." and "The strange thing about this is the fact that WGHP is one of my true locals. The tvfool report shows the transmitter is only 32.6 miles from my house."
http://www.tvfool.com/?option=com_wr...8e0301c3c04740
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Last edited by rabbit73; 10-Oct-2015 at 6:29 PM.
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