Saturday, June 10, 2017

180W Pallet Amplifier Using MRF9180


This is my first time to play with the 180W pallet amplifier kit from China. The kit comes with only a printed schematic but there was no details for the input transformer and the coaxial balun. The bias for the LDMOS is not also indicated so I have to download the datasheet of the MRF9180 from the internet.

The input transformer has a 9:1 impedance ratio so it has a 3 turns in the input while a single turn in the output. Connected to the drains are the 25 ohm teflon cables. This coaxial transformer is responsible for stepping up the low impedance drain to approximately 25 ohms. Next is a 50 ohm cable used to combine the 25 ohm balance signal into 50 ohm unbalance at the output. I choose to cut this cable to 15cm so that pallet operation would be optimal at the fm broadcast band.

The datasheet says that for MRF9180, gate voltage bias may be set anywhere between 2 to 4V but in my amplifier the VGS was set to 2.2V. At full output power, the pallet amplifier is consuming around 8 to 10 amps at 24V dc supply.


After the test, I was getting 150W at 144MHz (2W) drive and 200W at 100MHz (1.5W) drive and this pallet amplifier is remarkably broadband. The test was conducted without the LPF at the output.
--- 73 de du1vss.
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30 comments:

  1. UnknownJune 27, 2017 at 11:20 AM

    Hi how do i wound the transformer tr1?

    ReplyDelete
  2. hevirredJuly 1, 2017 at 1:59 AM

    The transformer is a 1:9 therfore the turn ratio is 1:3, the single turn goes to the gates of mosfets while the 9 turns is the rf input.

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    Replies
    1. UnknownOctober 3, 2020 at 4:33 PM

      Sir , can you give me the view on how to wined the transformer, im still in the dark of doing it. Pls help.tnx

      Delete
  3. UnknownJuly 24, 2017 at 8:15 AM

    thanks

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  4. UnknownFebruary 12, 2018 at 9:12 AM

    This comment has been removed by the author.

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    1. UnknownFebruary 12, 2018 at 9:36 AM

      the capacitors are (100N + 10N) or (10N + 1N); I ask because some Chinese give big and some small capacitors

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    2. UnknownFebruary 13, 2018 at 12:32 PM

      finally I was able to read the schematic clearly, thank you very much.

      Delete
    3. hevirredFebruary 18, 2018 at 7:29 PM

      The kit comes with 0.01uF and 0.1uF smd capacitors and please be aware that these caps dont have label printed on them. You have to test it to determine which one is 0.1uF. The bigger caps are all ATC cap and is used for LPF and output balun section.

      Delete
    4. carjoiaMay 23, 2019 at 12:28 PM

      tenho um modulo deste, mas não passa de 40w. Porque?

      Delete
  5. UnknownFebruary 22, 2018 at 2:50 PM

    their capacitors have fainted.but i didn't know if I had to use them,because som Greeks use 0.01 and 0.001mf.but i see your schematic and I'm ok.I am thankful.

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  6. UnknownFebruary 23, 2018 at 1:03 AM

    my english is bad

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  7. hevirredFebruary 25, 2018 at 7:54 PM

    This comment has been removed by the author.

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    Replies
    1. hevirredFebruary 25, 2018 at 7:55 PM

      You're welcome, thanks for visiting my site. 73 de du1vss.

      Delete
  8. UnknownJune 15, 2018 at 3:25 PM

    This comment has been removed by the author.

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  9. UnknownJune 15, 2018 at 3:30 PM

    Hello again I am Kostas lafazanidis. I want your help. I can adjust the output of the transmitter to 75 hom? I want to use an open dipole(75 hom),with 75 hom cable.I will not use LPF.

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  10. hevirredSeptember 20, 2018 at 6:03 AM

    no, but the amplifier is tolerable with an swr of 1.5:1 from the open dipole antenna. there is no need to modify the amp.

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  11. UnknownOctober 25, 2018 at 9:45 AM

    thank you again

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  12. eglkFlyerAugust 5, 2019 at 1:50 AM

    Hi. Thanks for your article,very much appreciated. I wonder if you have any tests done at 70 MHz?
    DE G8KWX

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  13. ik5pwsSeptember 20, 2019 at 7:36 AM

    Hi, just a more question about input transformer, you say "The transformer is a 1:9 therfore the turn ratio is 1:3, the single turn goes to the gates of mosfets while the 9 turns is the rf input."

    please, how many turns have you done in primary winding?
    3 or 9?.
    I got a chinese kit and i found a short piece of small wire, too much long for 3 turns but not enought for 9 turns.
    Based on instruction I made 3 turns but i still have SWR (1:2.5)
    Can you help me?
    best regards

    Stefano
    Ik5pws

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    Replies
    1. Ang paglalandi ni MarilouSeptember 22, 2019 at 4:54 AM

      Sorry it should be 3 turns in the primary and single turn in the secondary..

      Delete
  14. UnknownSeptember 20, 2019 at 6:18 PM

    Sir yung reistor na10 ohms 2 pcs . Located sa gate ng power trans. anung klase na reisitor yun sir. Tnx pk

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  15. AnonymousMarch 20, 2020 at 1:31 AM

    Untuk FM, berapa cm kabel feeder 25 ohm yang harus saya ukur.
    Ada yang mengatakan 15 - 17 cm

    ReplyDelete
  16. BuDs™ KuLoTJuly 24, 2020 at 7:27 PM

    Newbie here, mga boss sa gate ba mag measure ng bias voltage?

    ReplyDelete
  17. BuDs™ KuLoTJuly 24, 2020 at 7:27 PM

    Newbie here, mga boss sa gate ba mag measure ng bias voltage?

    ReplyDelete
  18. UnknownSeptember 16, 2020 at 12:59 AM

    Sir,
    With no lpf used, is there interference in other wireless signal

    Thanks
    Fgboko

    ReplyDelete
  19. AruxNovember 14, 2020 at 4:37 PM

    I have 100w kit with mrf 186 , can i replace by mrf 9180 directly without modification ?

    ReplyDelete
  20. UnknownOctober 15, 2021 at 10:43 AM

    Can I use thisciecuirt to 174-200mhz to bosst tv transmitter?

    ReplyDelete
  21. Vagner GomesNovember 21, 2021 at 4:31 PM

    This comment has been removed by the author.

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  22. Vagner GomesNovember 21, 2021 at 4:33 PM

    HI guys! I got this Chinese amplifier but I got only 70W output RF power in 80MHz. Anyone could me say anything about this my result? I think it that the transistor is false.

    ReplyDelete

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