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Discussion in 'Electronic Basics' started by Treeline, Feb 21, 2005.

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  1. Treeline

    Treeline Guest

    I cut in half a twin-lead antenna wire, typical 300 ohm wire. I inserted a Balun transformer on the
    first cut end to make it 75 ohms and connect it to an old TV.

    So far, so good.

    Then I got to thinking and that was bad. How can I reconnect that twin-lead that I cut in half, in
    case I wanted to use the other, unused end? And still keep that Balun transformer on that end?

    Hmmm, can I use the already terminated 75 ohm Balun transformer and connect it back up to the
    second half of the twin-lead antenna wire?

    Can I untransform or re-transform the 75 ohm Balun transformer to a 300 ohm thingee?
    If the first balun is 4:1, can I get a 1:4? Without too much dB loss.

    I found some RCA VH104 Signal Separator/Combiners in a dollar store.

    If I connect the balun transformer to the VHF OUT/IN
    to the UHF OUT/IN - will this so the trick?

    In other words, I am using just the inputs to really do the transformations, not exactly what the
    device is set up for.

    I am wondering if I can get a schematic of this part somewhere to see what it is doing internally.
    I guess I could cut the box apart but probably buying more wire and forgetting about transformers
    would be easiest. Read that these wires, twin-lead, do not last as long as coax but with the
    exposed antenna wire, wrap that with good electrical tape, probably last a long, long time. Maybe
    not.

    Supposedly it, RCA VH104, takes a twinlead 75 antenna and a 300 ohm coaxial cable and combines them
    to output into a coax with the single wire, what I might call a male connector but it's call an F
    type.

    And I assume it can do the opposite, take an input of the coax and separate it into 75 twin-lead
    UHF and 300 ohm VHF outputs.

    Come to think of it, would it be better just to connect the twin-lead directly to the TV which as
    inputs for this for it's inside antenna? It has screws for the two rabbit ears and another set of
    screws for a loop antenna.

    I did just now try to connect 2 baluns together. Very slight drop in image. Noticed one spec said
    0.5 dB loss between parts on these splitters and so forth. So this question might be rhetorical.
    Did ask in electronics design but one response suggested I was a toll so thought I would ask in the
    electronics basic newsgroup instead.
     
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