online-shashki Forum Addicted Member
Join Date: May 2002
Location: Where ever I am is where I am.
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Yes. A 3 way has more loss than a 2 way. A 2 way splitter will cut the received signal in half per port. A 3 way with cut the received signal by 66% per port. Remember each 3 db halves the signal. Putting two 2 way splitters in series with each other will drop the original signal by 75% on the two ports of the second 2 way splitter. But the opposite is true with an amplifier. Each 3 db will double the signal.
One thing you might want to consider using instead of splitters, use taps. That is what the cableco's use to keep loss down. A tap will have a 5db loss per port. The tap works where you have a main trunk line and the tap, taps off the main line. You won't get a tap at Radio Shack, but you can get them at speciality TV shops and off the net. They are couple bucks each. Taps are what I use so I don't have to worry about adding all those losses up. I know what the gain is at the head of the trunk and I know each tap will be 5db lower than that with just a little more loss due to the cable run. Less amplifiers too so less cost!
When analyzing signal loss, you have to add all the splitters loss and any amplifier gain to determine total system loss/gain. If your antenna is a 15 db gain antenna, and you have 12db of attenuation in the line due to splitters, the signal that reaches your TV is only 3db above the original signal presented at the antenna. Not a good result. If you need to split, find amplified splitters or use low gain amplifiers (10-15db MAX) ahead of the splitters to keep the gain unity through the system. The last thing you want is to overload an amp down stream. Amp overload will cause the signal to be distorted to the point, the receiver will not decode correctly and more than likely not decode at all. A good rule of thumb is you want the loss/gain ratio at the receiver to match the gain of the antenna. This will make sure you don't run the risk of overloading the receiver. Also, if your antenna location is within a mile or so of cell towers and such, your system can also be overloaded with high power gains as well. That is another reason to stick to the antenna gain figure at the receiver as well. Sometimes you still have to experiment if you live next to a cell tower or other high power transmitting site, like FM transmitter sites.
Yes, there is a little bit of black magic in this, but 98% of it is just using good common sense and the 3 db/unity gain rule.
All opinions expressed (unless otherwise noted) are the posters and NOT the posters employers. The poster in NO WAY is/will speak for his employers. "Arguing with an engineer is like mud wrestling with a pig. After a couple of hours, you realize the pig likes it"