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Impedance transformer or antenna amplifier - what is the difference and which on

Jankesik 129668 40
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Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
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  • #31 20096960
    G.R.
    Level 17  
    I understand that in my case the amplifier is not needed, and is the impedance transformer necessary for my antenna?
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  • #32 20096973
    sq3evp
    Level 37  
    BiQuad is approximately 50 ?. It will work but there will be noise and noise sensitivity due to this
    Use a transformer to match the symmetrical antenna to the unbalanced conductor.
    There are many ways, but it was what my colleague suggests, that is:
    balun from ASR "Telmora" antennas, which have a 1: 1 ratio (75 ohms symmetrical to 75 ohms unbalanced)
    Another way is described on the net, but requires a transformer tuned to a specific frequency. Here you have TV reception, so it will be better than Telmor antennas

    Quoting the issuer's forum:
    (...) There should be a 75 ? / 75 ? balun. If you connect without symmetrization, nothing big will happen, but the antenna radiation pattern will be distorted, and the cable braid will radiate energy (at the receiving antenna it will pick up interference). Symmetrization can be done by using a ferrite ring on the cable, making a loop of a few turns of the cable next to the antenna (...)

    I did tests with the Quad antenna - it was an improvement with 3 coils of 75 ? wires, diameter at about 5-6 cm. As if less noise could be heard.
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  • #33 20097072
    G.R.
    Level 17  
    I have just been looking for such a balun and I have a problem, I have nowhere found ASR Telmor or someone could tell me where I can buy such a model, I will be grateful for your help.
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  • #34 20097107
    sq3evp
    Level 37  
    G.R. wrote:
    I have just been looking for such a balun and I have a problem, I have nowhere found ASR Telmor or someone could tell me where I can buy such a model, I will be grateful for your help.


    Post in advance - test, check.
  • #35 20097204
    irekr
    VIP Meritorious for electroda.pl  
    A moderately advanced electronics engineer will convert each balun made on a ferrite core from the 300/75 ohm transformation to 75/75 ohms in a dozen or so minutes. It is enough to have soldering irons and an ohmmeter.
    This is the problem of connecting the ends of this balun.
    There is indeed a problem with Telmorowski 75/75. They are hard to get, unless they are surplus, they are often badly damaged by time.
    It can also be based on coaxial cable loops, but it takes longer and narrows the antenna frequency response.
    I used to make such baluns by winding a bifilar coil on a pencil with 0.5 mm wire with 3 or 4 turns insulation. In real current conditions, this is a problem of mechanical fastening of the ends. In the worst case, I attached such a wire balun to the original plate of the IV-V band balun - made on strip lines - where the strip lines were cut off and the ends of the balun were soldered to the antenna lugs and cable clamps. 15 minutes of work.
  • #36 20097253
    bratHanki
    Level 38  
    To complete the previous statement, I will add that the line on which the ferrite baluns are wound has an impedance of 150?.
    The whole philosophy with the conversion of 300/75 to 75/75 is to desolder the wires from the common point and connect the same as on the other side, i.e. white with white and yellow with yellow.

    Impedance transformer or antenna amplifier - what is the difference and which on

    Taking the opportunity, I will ask what are these baluns, because I have several. I have drawn the connections and it turns out that they are 2 4: 1 transformers connected in series, 16: 1 in total, i.e. 300 / 18?.
    Impedance transformer or antenna amplifier - what is the difference and which on
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  • #37 20098223
    sq3evp
    Level 37  
    bratHanki wrote:
    4: 1 transformers connected in series, 16: 1 in total, i.e. 300 / 18?.


    This is also the case, but I'm afraid that it is not 300/18 but 800/50.

    99.99% of cases - radio frequency matching transformers are made for 50? or 75?.
  • #38 20098306
    G.R.
    Level 17  
    irekr wrote:
    A moderately advanced electronics engineer will convert each balun made on a ferrite core from the 300/75 ohm transformation to 75/75 ohms in a dozen or so minutes. It is enough to have soldering irons and an ohmmeter.
    This is the problem of connecting the ends of this balun.
    There is indeed a problem with Telmorowski 75/75. They are hard to get, unless they are surplus, they are often badly damaged by time.
    It can also be based on coaxial cable loops, but it takes longer and narrows the antenna frequency response.
    I used to make such baluns by winding a bifilar coil on a pencil with 0.5 mm wire with 3 or 4 turns insulation. In real current conditions, this is a problem of mechanical fastening of the ends. In the worst case, I attached such a wire balun to the original plate of the IV-V band balun - made on strip lines - where the strip lines were cut off and the ends of the balun were soldered to the antenna lugs and cable clamps. 15 minutes of work.

    I also have a question whether it matters on what ferrite I will make the semitrizer, I found a ferrite in the shape of a circle with an outer diameter of about 1 cm and I would make a 1: 1 transformer on it.
  • #39 20098321
    sq3evp
    Level 37  
    It is of key importance - the ferrite from which the balun is built is important.
    Different material is for Kf ( 1GHz.
    The issue of material wastage for a particular frequency.
  • #40 20098327
    G.R.
    Level 17  
    So what will be the best 300/75 ohm series balun to convert it to 75/75 ohm?
  • #41 20098430
    sq3evp
    Level 37  
    Well, for sure, not only printed on the core.
    Something like this or this

    So illustrative: Impedance transformer or antenna amplifier - what is the difference and which on
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Topic summary

The discussion revolves around the differences between impedance transformers (baluns) and antenna amplifiers, particularly in the context of improving TV reception. A balun is essential for matching the impedance of the antenna (often 300 Ohm) to the receiver (75 Ohm), preventing signal distortion. Amplifiers should only be used when signals are weak and not to compensate for poor antenna performance. Users discuss the necessity of a balun in their setups, with recommendations for specific antennas and cables. The consensus is that if the signal is adequate, an amplifier may not be needed, and a 75 Ohm coaxial cable should be used. The importance of using the correct components to avoid signal loss and distortion is emphasized.
Summary generated by the language model.
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