uses for 75 ohm coax in Amateur Radio

Discussion in 'General Technical Questions and Answers' started by KJ4GXU, Sep 5, 2009.

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  1. RU9CA

    RU9CA Ham Member QRZ Page

    No problems - use the cable 75 ohm.
    All antenna, for cable 50 ohm, usually beautifully work and cable 75 ohm.
    Besides, you have an excellent possibility to connect parallel this cable and get the feeder 37.5 ohm - excellent for feeding the antennas GP.
    Or supply the frame ( the lazy delta ) through 2 cables in symmetrical cut-in. The feeder 150 ohm are Got.
    And certainly, always possible use the repeater. Take the cable to electric long equal half of the long wave. In this case - feeder repeats the resistance of antenna. And - his wave resistance already is not important much.
    For example - see figure
     
    Last edited: Sep 5, 2009
  2. K9ZMD

    K9ZMD Subscriber QRZ Page

    Money vs. SWR: This Perspective Bears Repeating

    "I would certainly use the free 75 ohm coax before I would use my social security check to buy 50 ohm coax" (With full credit to Cecil, W5DXP, 9/5/2009)
     
    AE0DM likes this.
  3. K8ERV

    K8ERV Ham Member QRZ Page

    Right, I got it backwards, he got the 58. But it worked ok.

    TOM K8ERV Montrose Colo
     
  4. AG3Y

    AG3Y Guest

    I can remember when we re-wired the studios for Maryland Public Television. There were MILES of RG-59 cable in the cable ladders that ran through the tunnels beneath the various control rooms and studios. When the new equipment was put in place, we had to pull hundreds of feet of that stuff out, to make room for the new cables.

    I will never figure out why they didn't keep and use the old stuff! I suspect it had to do with "timing"which changes the phase of the chroma signal, but I will never know for sure ! All signals have to propagate the same distance, whether the studio is close by or far away , so every studio was wired with the same lengths of coax. Some of the cables were folded back on themselves a couple of times !

    That's your State Government funds at work !


    P.S. Tom, that's OK, I'll attribute it to a "Senior Moment" Coming closer and closer together, aren't they? ;) :eek:
     
  5. K8ERV

    K8ERV Ham Member QRZ Page

    Nah, just one big long continuous one. But it's better than the alternative.

    TOM K8ERV Montrose Colo
     
  6. AG3Y

    AG3Y Guest

    Ahhh, I see, NOW we are COUNTING NUMBER of OCCURANCES ! Well, I guess that puts you in a position ahead of me. I have several, you only have ONE !

    Now, I understand ! ! !
     
  7. K9KXW

    K9KXW Ham Member QRZ Page

    Frequency Limitations (?)

    I'm sorry to add a question to a question here, "BUT" is there any limitations as far as which frequencies or bands that this entire thread is talking about whether is be 160-6 meters, 2 meters or 440 MHz ? :confused:

    Thanks and 73 Jim
    KC9KXW
     
  8. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Theoretically 75 ohm coaxial cable has a lower attenuation versus frequency and therefore will be slightly better on the higher frequencies than 50 ohm cable. Basically, the diameter of the cable generally has the most effect on the attenuation. That is the larger the diameter of the cable the lower the attenuation.

    Using 75 ohm coaxial cable is pretty much universal in broadcast television reception. The reduced losses in the cable is definitely one of the reasons that this type of cable is used.

    Glen, K9STH
     
  9. K9KXW

    K9KXW Ham Member QRZ Page

    So I take it that 75 ohm coaxial cable is a little better for VHF/UHF Frequencies since TV stations run the higher bands, especially with the new (DIGITAL-TV) that's being used today.

    Please correct if I'm wrong, I'm trying real hard to understand what everyone is saying here........

    Thanks and 73 Jim
    KC9KXW
     
  10. KA9MOT

    KA9MOT Ham Member QRZ Page

    I run 75 Ohm out to my Fan dipole.....Works great.

    Hmmmmm.....are you guys tired of hearing about my Fan Dipole yet?
     
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