Substitute for an antenna 300 ohm to 75 ohm connector?

Discussion in 'General Electronics Chat' started by frank55, Jun 22, 2015.

  1. frank55

    Thread Starter Member

    Dec 6, 2013
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    Hi guys; i'd like your opinion on this project i made for my roof top antenna,to substitute the matching transformer.
    first my Antenna rotator broke so i took it down and fixed it,it had some bolts that fell off then i had to take out the antenna 300 ohms to 75 ohms matching transformer,which broke upon unbolting it witch was bad luck,now i have no matching balloon an the worst part nowhere to buy it ,use to get stuff near here from Radio Shack which closed ,
    i have also installed a SVA15PRSM distribution Amp near the antenna and a 12v SVPI ,these items were installed before, but inside the house closer to the receiver.
    now story short,since i did not have the matching transformer ,i did not want to go by without tv i made a straight connection with coaxial cable ,took out the F connector and striped the coaxial wire connected ground wire to one side and the middle wire to the other, and for my surprise i never had so many chan and so good reception,but someone suggested me, due to water getting inside the wires to get a outdoor matching transformer.

    well made this strait wire to connect from the antenna to the amp

    as you see i cut 2 pieces of thin ground wire and connected and soldered an F type connector that i cut from type F cable connectors,
    what you think about this? will it work?i know i should go up there and try! but up there are 50 feet high and no easy access and i'm not young anymore, so will this work at least same way i have now? thanks

    http://postimg.org/image/d161lt343/ef75894e/
     
  2. BReeves

    Member

    Nov 24, 2012
    412
    64
    Lowes or Home depot will have the matching transformer.
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,538
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    Kroger, Staples, CVS ...
     
  4. frank55

    Thread Starter Member

    Dec 6, 2013
    253
    10
     
  5. frank55

    Thread Starter Member

    Dec 6, 2013
    253
    10
    thanks guys; but i think i 'm going to keep the way it is connected now, where i went from 34 chan to 60 and a better reception on all chan and get some red high temp silicon to seal the end of the cable where you stripped the coax
     
  6. frank55

    Thread Starter Member

    Dec 6, 2013
    253
    10


    And for someone out there that don't know better,don't waist money on matching balloons that end up failing very often, just do as i did, see pic,and add silicon to the striped ends,it will give you better signal and more chan,i tried this with and without balloon,and result without balloon you get better.

    http://postimg.org/image/osp3l70qh/e9c3dc75/
     
  7. BReeves

    Member

    Nov 24, 2012
    412
    64
    Because you were lucky and got away with what you did doesn't make it right for every situation. Maximum signal transfer only happens if the impedances of all components are matched.
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,538
    1,251
    Which raises a question. A 300:75 ohm balun (note: b.a.l.u.n) is a 4:1 voltage and current transformer. Eliminating the balun increases the open circuit voltage by 4:1. His results suggest that maybe the other end is a 300 ohm load rather than 75 ohm. Either way, the 4:1 increase in signal voltage certainly explains the change in receiver performance, and the receiver might have brains to eliminate ghosts caused by improper termination reflections.

    ak
     
  9. frank55

    Thread Starter Member

    Dec 6, 2013
    253
    10
    Or maybe because i'm using a SVA15PRSM cable distribution Amp with a SVPI 12v inserter as an antenna Amp, instead of a regular Antenna Amp.
    I have people telling me that this way without ballun only working with half an antenna, one side is grounded out by the coax shield.
     
    Last edited: Jun 25, 2015
  10. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,145
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    Aside: Mast mast mounted amps are preferrable. Use drip loops when you can. Use outdoor rated coax connectors. Use di-electric grease.
     
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