600 watt HF Linear Amplifier Project

Discussion in 'Homebrew and Kit Projects' started by KD8UYQ, Feb 9, 2017.

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  1. WB2GCR

    WB2GCR Ham Member QRZ Page


    Ripley, believe it or not, I could mod the LEDs pretty simply in the existing setup... :D
     
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  2. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Hi there,

    Yes sir, the IC regulator that I used is a 7812 fed from the 24 volt mastered power source on the power supply protection board. There is a twisted pair of wires running from the PS protection board on the bottom plate right along the input protection board, up along the coax cables for the input and output SO-239 connectors then right between the PA and LPF modules. In hindsight, not the best route to the 12 volt power supply board.

    One of the things that I will be addressing this evening.

    Ripley
     
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  3. SWL37632

    SWL37632 QRZ Member

    Ooops....that's what I get for relying on my senior memory. Checking the fairchild spec y'all be right regarding the 7800 regs being linear....now I know I had a certain reg series that used an internal switchmode architecture since it generated a whole lot of EMI on the board and had to tame it...just need to remember what it is now. This is going to bug me all night ... Bill Winston.
     
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  4. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Alright!

    I fixed two of the four issues with the amplifier this evening. 10 meters now works on manual and automatic mode without any relay chatter. I made changes to my little +12 vdc and bias relay board, replaced the two wires running from the master 24 volt supply to the input of this board with a shield two conductor cable, and rerouted the run away from the back panel where all of the coax cables live to along the front panel and behind the mu metal shield.

    Here is what my little board looked like before;

    STH70421.JPG
    And after the addition of two .1uf decoupling caps and one 220uH RF choke in series with the +24 line that feeds the input of the 7812 IC.

    STH70424.JPG
    Next up, I am going to tackle the 160 band and why the LPF relays for this frequency chatter in Automatic mode.

    I am making progress :).

    Ripley
     
    AF6LJ likes this.
  5. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    Good deal....
    These are the little things you learn when taking on a system level project like this.
     
  6. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Amen to that.

    As I said before, by the time I'm done I will know a whole lot more about RFI and how to deal with then when I started this project. Thank you all for looking over my shoulder as I try to short out the problems.

    Ripley
     
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  7. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    Always glad to help.
     
  8. WB2GCR

    WB2GCR Ham Member QRZ Page

    Uh oh...
    ...now there's the problem!!
    "
    as I try to short out the problem".

    Not sure that's the best possible approach! <wink>
     
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  9. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Good catch Bear.

    Big difference between sort and short

    I am terrible updating these posts in the evening

    Ripley
     
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  10. SWL37632

    SWL37632 QRZ Member

    Great!

    FYI...Another common issue which contributes to EMI/EMC issues is using small gauge wire for the interface cabling. Another big mistake is using a single return for multiple circuit high lines.... saves on money and launch/weight budget but wreaks havoc on avionics performance and creates a multitude of 'phantom' operational anomalies. BW
     
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