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.Jankesik wrote:it is lost at the signal level, in the case of the replaced cable ~ 4.5dB, i.e. the signal will decrease ~ 4x. But, in general, if the signal received by the antenna is good, it doesn't have to be a problem.I need about 27m. Do I lose quality with such a long cable?
Jankesik wrote:Each cable, apart from weakening the signal, will cause some distortions, because it is not a perfect waveguide (there will be some reflections, etc.), but there is probably no other option, so there is no need to think about this topic. I would rather be worried about the drop in signal level.I need about 27m. Do I lose quality with such a long cable?
mihal2002 wrote:A friend wants to buy a symmetrizator. The antenna, on the other hand, has an impedance of 75 Ohm, so as I wrote above, it is already in the box.What's this nonsense? Do you know what you are writing about?
mihal2002 wrote:The balun! If the signal is too weak, you need to adjust the amplifier, of course, power it from 5 to 12 V.
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rzeszutek1 wrote:Whereas the antenna has an impedance of 75 Ohm,
Jankesik wrote:
rzeszutek1 wrote:The balun is used to match the impedance of the antenna to the impedance of the receiver, cable, etc. Let's say that the receiver has an antenna socket with an impedance of 75 Ohm, we use a coaxial cable with the same impedance, and we need to connect it to a dipole antenna with an impedance of 300 Ohm. We then need a balun between the antenna and the cable to match these impedances. In short, if the antenna has a different impedance from the receiver, first you need to mount an impedance transformer, and then, if necessary, amplify the signal with an amplifier. If there is no impedance matching of all components, distortions (signal reflection) and more are created, so there is no point in using an amplifier without first matching impedance with a balun. To sum up, always a balun, and then possibly an amplifier, or 2 in 1.
TL;DR: A 27 m run of RG-6 cable attenuates TV signal by ≈ 4.5 dB, or ~4× power drop [Elektroda, Anonymous, post #10388099]; “amplifiers can’t fix a bad antenna” [Elektroda, irekr, post #10387360] Balun first, amp only if levels stay below –55 dBm [Ofcom, 2021].
Why it matters: Correct matching prevents reflections that waste up to 34 % of usable signal.
• Typical 4-step UHF balun cost: PLN 5–12 [Elektroda, Jankesik, post #10387440] • RG-6 loss: 0.17 dB/m at 600 MHz (≈ 4.5 dB per 27 m) [Belden Spec Chart]. • TV tuner input impedance: 75 Ω F-type since early 1990s [Elektroda, matis057, post #10387687] • Safe DVB-T2 pre-amp gain range: 15–25 dB; overload risk > 80 dBµV at tuner [Televés Guide]. • BiQuad raw impedance: 50–90 Ω, varies with build [Elektroda, irekr, post #20096847]
