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Quick simple DIY 50 OHM 16 watt dummy load

Discussion in 'Home Brew' started by Crossbow, Jul 18, 2018.

  1. Crossbow

    Crossbow Active Member

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    Here is a simple 16 watt 50 Ohm dummy load for your work bench.
    Parts needed:
    8- 100 Ohm 2 watt carbon film resistors
    1- Small piece of RG8 50 Ohm coax
    1- Small piece of pref board. Not needed but looks better.
    1- Med bottle, Or what ever you want to put it in.
    1- PL259, I have a quick connector attached to my PL259
    dummy4.jpg
    dummy1.jpg
    dummy2.jpg
    dummy3.jpg


     
    Tallman and Shadetree Mechanic like this.

  2. Robb

    Robb Yup

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    Did you also fill it with a little mineral oil yet?

    Nice job.
     
    Crossbow likes this.
  3. Crossbow

    Crossbow Active Member

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    Nope did not see a need for any mineral oil. Done some bench testing on her and she seems to be running cool. SWR is flat.
     
    Robb likes this.
  4. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Nice work, good job on pictures!

    If you wish - you can also use this...
    CrossbowDummyLoad.gif
    Regards!
    :+> Andy <+:
     
  5. loosecannon

    loosecannon Sr. Member

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    nice!

    if you wrap a few turns of insulated wire around that center conductor and run one end to a BNC connector you have yourself a nice little tap point to hook your scope to in order to view your RF power and modulation envelope.

    I also always tell people to build a 150 ohm dummy load as well, so they can set the SWR meters in radios.
    LC
     
  6. Crossbow

    Crossbow Active Member

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    Awesome job done Andy! Thanks so much for making that graft up!
     
  7. Crossbow

    Crossbow Active Member

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    Yes Sir that would help folks to get a tap.
    I only made this simple one up to plug onto a working radio for cross referencing a dead radio that is hooked up to my full test gear.
    I do not trust those little small 5 watt mini dummies that is sold on the market.
     
  8. rabbiporkchop

    rabbiporkchop Well-Known Member

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    Make sure they're carbon film resistors.
    Wire wound won't work.
     
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  9. loosecannon

    loosecannon Sr. Member

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    couldn't agree more Crossbow.

    i bought one of those ready made dummy loads on ebay and it measured close to 100 ohms LOL.
    LC
     
    Crossbow likes this.
  10. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

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    Interesting layout. If you jumper right in the middle the impedance remains the same 50 ohms. As pictured it is configured as two 100 ohm resistors in parallel for 50 ohms in series with another pair in parallel for another 50 ohms making 100 ohms. All that is repeated below so it becomes 100 ohms in parallel with 100 ohms for an impedance of 50 ohms. With the jumper it makes four 100 ohms resistors in parallel for a total of 25 ohms in series with another four in parallel for another 25 ohms making the total impedance again 50 ohms. Oh man............why did I analyze that to that depth? I think I spent too much time in the sun today. Oh well at least my truck is super clean inside and out now.
     
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  11. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Easy, Easy...take a deep breath...

    You can "spread" the power dissipation thru an array "laddered" like that - and even use 150 ohm 2W Carbon Comp - only with 3 on each "branch" of the tree. Did up that for my own shack for the T/S "Test bench" stuff - or using things like the Emperor TS-5010 or HR2510 which had a little more oomph than the little "4-watter" would take safely.
     
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  12. Crossbow

    Crossbow Active Member

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    WOW that is crazy! Glad I did not waste my money to try one! Thanks for the heads up!
     
  13. Crossbow

    Crossbow Active Member

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    Love seeing brain power put to use! See ya needed a break after being out in the sun so long getting your baby all washed, waxed and detailed up.
     
    Captain Kilowatt likes this.
  14. Crossbow

    Crossbow Active Member

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    Yes Sir that is another way to do one but would only be 6 watts and I wanted something to go at least 10 to 12 watts to be on the safe side. I think with having 16 watts I should be safe for normal CB testing. Beat the heck out of changing coax over or having a switch box dragging coax around getting in the way. Just something simple and out of your way kind of thing.
     
  15. Crossbow

    Crossbow Active Member

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    Great point! I did forget to add that in my list but Andy put it in his awesome graft layout.
     

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