Hello, thanks for your replay, the problem is that my antena is on the top so i need like 30m coaxial and if i put 30m RG6 is not good , thats why i have now Ecoflex 10 but is 50 ohms, i will put it anyway becuse the preamplifier is 50 ohms, but the problem is that trv is 75 ohm, i dont know anymore what to do, believe me, i am thinking and thinking and my brain want to explote, Why electronic is so complicated? why MMIc are only 50 ohms? Sometimes i think that i am the person that give me myself all this problems, Here in Peru you cant find one good antenna, all antennas are home made, any shop sale good antena, so i have to build my antenna myself, next, i live in the first floor, i have to use 30m coaxial, i got one very expensive in holand but is 50 ohms, if you need a good amplifier for all uhf band you have to buy the one with MMIC, but is also 50 ohm, and tv are 75 ohm, so why like this so complicated.
Thank you.
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At one time the nominal impedance of TV antennas was 300 ohms. These were yagi type. When 50 ohm coax lead became the style, there were matching transformers. Attach it to a 300-ohm twin lead connection, and you had the output through a 50 ohm F connector.
It's possible you could use the same matching transformer. Or, find its schematic to supplement information you have now.
Thanks for your replay, if you say this that antena no have the output 50 ohm, how is posible to conect it to 75ohm tv? Why the best antenna preamplifier are 50 ohms? 50 ohms, 50 ohms, everywhere i reed i see 50 ohms, matching network, loose power....., if you dont put correct impedance and things are not so easy to understand for me at list.
Thank you
Alberto.