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Any hams or RF guys? I had an interesting hour at work today.

Discussion in 'The Lounge' started by newyorkin, Oct 3, 2006.

  1. newyorkin

    newyorkin 1 ton status

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    I ran a 25,000 watt transmitter into a dummy load with no fan on it for over 20 minutes. :eek1:

    (If you're not sure what I'm talking about, radio transmitters need to have their output go to an antenna, or what's called a dummy load, something that will basically absorb and dissipate the energy safely).

    The transmitter remote controls did some freaky stuff, switched the backup transmitter (which is normally turned off) into the main antenna and main transmitter into the dummy load, then turned them both on. Then the remote controls failed, so I had to hightail it up to the site to check the conditions and shut down the rogue transmitter... 5pm, in rush hour traffic. I normally can make the ride in 10 minutes in a panic mode, today, when time was crucial, it took way longer. My bike started overheating while I was stuck in traffic, but I knew I didn't have time to pull it over, so I pushed it right on the red line... :doah:

    When I got there, the dummy load internals were glowing bright red and some resistor clamps were actually molten and dripping. It has a fan, and used to have an interlock so the transmitter couldn't be started without the fan on, but another engineer I work with disabled that interlock a few months ago with no real explanation of why. I turned on the fan and killed the transmitter, but after about 2 minutes, the fan started clanking. When I turned it back on later, the fan sounded like the blades were hitting something, so I'm sure it's melted.

    Anyway, I'll probably take apart the dummy load tomorrow morning. Pics of the carnage to follow (:rotfl: if this post actually gets any replies).
     
  2. Stickseler

    Stickseler 3/4 ton status

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    Pad :p:



    And I dont have a clue what your talking about, but it sounds cool, wheres the pics
     
  3. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    Smoke'em if you got'em.....loads and bikes.:crazy:
    George
     
  4. newyorkin

    newyorkin 1 ton status

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    :haha: :haha: :haha: :haha:
     
  5. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    I read dummy load and had impure thoughts.
     
  6. newyorkin

    newyorkin 1 ton status

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    Quite common response if you aren't familiar with the equipment.

    :rotfl: That could actually have two meanings...
     
  7. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    Actually I knew what it was in the back of my mind, but my brainwaves have to pass through the "guy" section before they get to that point.
     
  8. ntsqd

    ntsqd 1/2 ton status

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    At 25k is it still coax, or do they call it waveguide?
    We put two 10k RF power supplies on the HP3500 Ultra High Vacuum Sputtering chamber. Those, each, were scary enough.
     
  9. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    My first experience with a dummy load was dropping my dads old heathkit unit ( remember the paint cans LOL ) on my foot when I was 5 :thumb:

    The stuff you are talking about he would know about , he is the director of engineering at the now CW network station in Tucson .

    I never went into his field , but I did spend a summer cutting and routing cables on some remote trucks being built . And helped install a Klystron one summer for channel 45 in Phoenix when dad worked there ( just lifting and being dads gofer ) :thumb:
     
  10. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Hell yes I want to see pics. The biggest thing I get to use is the airborne HFs. They only push ~200 watts.
     
  11. Z3PR

    Z3PR Banned

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    Bring on the pics. I may not have a ham ticket, but I've been know too play with radio equipment. I'd like too see the carnage.
     
  12. diesel4me

    diesel4me 1 ton status Premium Member

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    radio wave!..

    I've only messed with CB's and a few old tube type ham radio's and linear amps in the past...I used a 6V dashlight bulb as a dummy load on the CB's--only 5 watts,so not much potential of overheating anything!..not much excitement there!...:rolleyes:

    I have been inside a radio station towers transmitter "booth" once ,many years ago..the guy knew my dad that maintained the transmitter..he showed me the "arc gap" that lightning would jump across if the tower was struck by lightning!--it had a copper ground strap about 3" in diameter!..the station put out 50,000 watts of power,and you could "feel" the radio waves as you entered the property!..looked like a sub-station for a power company inside!..:crazy:
     
  13. roadnotca

    roadnotca 3/4 ton status

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    Talking about getting religion, point that thing away.:haha:
     
  14. newyorkin

    newyorkin 1 ton status

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    The carnage wasn't as bad as I was expecting, but still kinda bad. I'm guessing the unit got over 500 degrees. At what temp does aluminum glow?

    These are the pics of the unit, some melted wiring, severely distorted air dam, and a shorted resistor.

    DSC00401.JPG

    DSC00404.JPG

    DSC00405.JPG

    DSC00407.JPG

    DSC00409.JPG
     
  15. newyorkin

    newyorkin 1 ton status

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    Yup, waveguide, but it's technically still coax. Going into the load we use 3-1/8 rigid copper, like big plumbing pipes. Going up to the antenna, we use flexible waveguide, Heliax, etc.
     
  16. 79Stomper

    79Stomper 1/2 ton status Premium Member GMOTM Winner

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    Well I was going to chime in, but that stuff is unreal.
    I am not a HAM operator or anything, just been doing tactical radios for the past 11 years or so. Biggest thing I have operated was an old HF radio, put out 400w. With my dipole I could get about 800 mile sout of it, but with one of my field expedients I could talk to units all over the world. Now I am more of a UHF Satellite person and deal with new Digital HF equipment occasionally to pass data.
     
  17. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    I only have one thing to add to this thread...









    MOTHER OF GOD!!!
     
  18. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    Not quite but you might be able to use this to call her...........:haha:
    George
     
  19. newyorkin

    newyorkin 1 ton status

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    These are pics of the antenna after a lightning strike. The slagged part is the inner conductor, the exterior part with the burn is where the melted internal part was. When this actually happened, the main transmitter wouldn't stay on, and when I flipped on the backup transmitter, it literally started arcing and shooting sparks out of the top of it. It was like watching fireworks in a 9'x20' building with a 10' ceiling.
    RF is pretty cool, is a awe-inspiring what it can do when you lose control of it...

    Tower1.jpg

    DSC00370.JPG
     
  20. readymix

    readymix 3/4 ton status

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    Sweet.

    I was working on a shipboard transmitter once a few years ago.
    The spark gap fired a few times earlier that day so we were trying to T/S the issue.

    After a little while of hot checks we decided to take a break. When we came back we realised that the SG had broken and we were putting 55KW into an air cooled 5.5Kw heat exchange DL........Yeah, that is 10x too much. The whole area smelled for a few weeks.
     

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