TV Antennas

[Stupidbaker]

Birds, squirrels and such displaced parts of a big antenna. I'd see a bird land on it and tilt a side way off from center. So I went up on the roof and tied small aluminum wire knots here and there for support. Signal is much better, but now when a train goes by, there's about a minute or two of sketchy TV. So I plan to raise it up another 15 feet. That means the coax cable will be at least 50 feet. While I am at it, I might as well run to a second TV. So I guess I would need two impedance matching modulators or whatever they're called. Should I hook two of these things (impedance matchers) to the same place on the antenna, or should I run one cable from one impedance matcher, then split the signal to the two TVs?

 

[duke37]

The best place for an antenna amplifier is at the antenna. Power goes up the co-ax cable. The signal can then be split to two cables in a more convenient place.
The amplifier will not be needed if the signal is strong and may even cause problems.
A splitter can as simple as a few resistors but attenuates the signal. You can get distribution amplifiers which will take in FM and TV frequencies and provide two or more outputs.

 

[Stupidbaker]

The best place for an antenna amplifier is at the antenna. Power goes up the co-ax cable. The signal can then be split to two cables in a more convenient place.
The amplifier will not be needed if the signal is strong and may even cause problems.
A splitter can as simple as a few resistors but attenuates the signal. You can get distribution amplifiers which will take in FM and TV frequencies and provide two or more outputs.

Thank you for your time and response. Please allow me to make sure I understand.
First of all, you are suggesting an antenna amplifier. Is that a device I plug into an external power source, or is that the same as the in-line thing I was calling a modulator. I don't know what a modulator is - don't even know why I used that term. I meant impedance matching transformer. An impedance matching transformer is not the same as an amplifier is it?
Next question: Are you saying that I might attach an amplifier directly to the antenna, then another section of coax cable from the amplifier to a conveniently located splitter? But also, I think you are be suggesting there may not be a need for the amplifier.
Finally, how many if any, impedance matching transformers are needed for my project? Should I have one before the splitter and that is all, or should I have two - placing each after the split?

 

[duke37]

A modulator is a device to mix two signals together such as an audio or visual signal onto a radio frequency. You do not need one of these.
You do not need an impedance matching transformer if the system all works on 75Ω. My simple FM antenna is 300Ω and so I use 300Ω twin feeder to the amplifier/splitter where there is a 300Ω to 75Ω balun. The balun uses a ferrite bead and was rescued from a loop antenna on a portable TV.

The need for an amplifier depends on the signal strength. Insufficient signal strength means more noise on the signal when further amplified. Too strong a signal can give distortion generating cross modulation. I would think that amplifying close to the antenna may be necessary with 50ft of cable attenuating the signal.
I have about 10ft of cable from the antenna to a distribution amplifier in the loft (so it is dry) and this has four outputs to feed various rooms. It takes in FM also.

Power will need to be provided to any antenna amplifier, this can be sent up the co-ax cable in a similar way that satellite receivers work. In my case, the amplifier is fed with mains directly.

A spliitter will attenuate the signal so you could amplify the signal to compensate for this but my amplifier does the splitting to give the four outputs. I use a resistive splitter if I need separate FM and TV signals from one down lead.

I spent many hours in my youth as the servant of my brother, carrying a TV antenna on a long mast to find the best place for it. I only just managed to avoid falling off the roof.