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Rectifier location?

Discussion in 'Home Brew' started by GnG8d, Nov 20, 2011.

  1. GnG8d

    GnG8d Well-Known Member

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    If you had a transformer in one building, and an amplifier in another, where would you rectify the current?

    Would you rectify it at the tranformer and send off the DC, or would you pipe in the AC and rectify at the amp? I can see pros-cons for both, but what keeps sticking out in my mind is the DC picking up noise between the 2 and needing refiltered (ie security light, etc) or, it could be rectified at the tranformer and filtered at the amp maybe?

    Opinions?


     

  2. Robb

    Robb Yup

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    Don't know if I can answer your question; but here is a thought.

    When the choice for either AC or DC was being argued back in the day - as to which one would be used on the national level power grid - AC was chosen over DC because it doesn't degrade in strength over distance as DC will.

    But this also depends on how far a run too.

    I would choose AC - in regards to your question.
     
    #2 Robb, Nov 20, 2011
    Last edited: Nov 20, 2011
  3. W5LZ

    W5LZ Crotchety Old Bastard

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    Ditto the AC. The voltage drop with DC would probably out weigh it's use.
    - 'Doc
     
  4. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Actually it does for the same voltage whether it is AC or DC however by using transformers to step up the voltage and drop the current much better efficiency is achieved by having far less I-squared-R losses in the wires.
     
  5. GnG8d

    GnG8d Well-Known Member

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    Funny the whole history of AC/DC was brought up. Not too long ago a group of us were standing around talking and the origins of it got brought up. This group was NOT electrical in background. I had heard of it the battle, but never really new why AC won out, however the first thing that came to my mind was the ability to use transformers in an AC grid ............ you have my curiosity peaked now, I'm going to go back and read some of it when I get time.
     
  6. GnG8d

    GnG8d Well-Known Member

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    I think this will be the whole basis of AC winning out.

    But still the question remains ....... where would you rectify the AC in a situation where the transformer is divorced by 100' or more from the amplifier.
     
  7. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Would it really matter? The current thru the system is the same regardless of where the rectifiers are placed and the voltage drop will be the same so therefore put them wherever it is the most convenient. The only difference I can see is if you wanted to use a Variac to vary the voltage somewhat then that may determine where they are located but then again convenience is the determining factor.
     
  8. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Well if my memory is even close:
    Edison and GE were working with DC transmission lines...

    Tesla(Father of the AC Motor) and Westinghouse were using AC transmission lines...

    CK: Was it not AC transmission that won out due the the increased in conductor size required to maintain the supply voltage...ie... using DC the wire resistance is double that of AC transmission with equal currents

    Where the entire single conductor length must be accounted for from source to return point in DC....

    Where as AC due to the shift in phase between the (2) conductors only half the resistance is measured at any point in the transmission....

    That's some theory I have not thought about in awhile!
    Am I getting old or???:D
    All the Best
    BJ
     
  9. hagueok

    hagueok Member

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    just how big is your radio? wow
     
  10. GnG8d

    GnG8d Well-Known Member

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    How, when AC tries to "skin" and DC doesn't?
     
  11. Shockwave

    Shockwave Sr. Member

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    AC won out over DC transmission lines because DC had to be sent out at the user voltage of 110 volts DC. This extremely low transmission voltage meant the current in the lines would be tremendous and required large conductors. With AC the transmission lines could be run between 2400 and 11,900 volts AC with distribution transformers on the poles to step the voltage down to 110 and 220 volts. This loss is only effected by the voltage and not the fact it may be AC or DC. The difference is DC cannot be stepped up or down with transformers alone.

    To answer your question I would rectify inside the amp and run AC from the transformer. The only reason being is that it's probably safer to have the rectifiers enclosed inside the amp then having them exposed at the pole pig. I like to use two runs of RG-213 coax with HN connectors installed to carry the HV from the pig. They don't pull out like the James Millen HV connectors and you can safely shield the HV inside the braid if you ground the braids. That way if the wire is ever crushed or it's insulation is pierced, the HV will arc to the grounded shield before it can bite you.
     
  12. GnG8d

    GnG8d Well-Known Member

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    That's what I'll do Shockwave, as CK suggested, it is the most convenient way and I have a 200' piece of LMR400 here already.
     

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