600 watt HF Linear Amplifier Project

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

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  1. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Thinking about it a little bit more, I bet that all that happens with the Icom, ALS-600, and LDG antenna tuner setup is the ALS -600 is also put in standby mode during the antenna tuning operation. Nothing more than that.

    In a nutshell, the LDG automatic antenna tuner is designed to tune the exciter by bypassing the linear amplifier then when antenna is matched to the radio the linear is taken out of standby mode and brought back on line.

    Looking back, when I first started this project I knew nothing about building a linear amplifier, then I gained a thimble full of knowledge, and now I am up to half a teacup. :)

  2. RICHS

    RICHS QRZ Member

    Hello, nobody has heard much lately about your project?? I am especially interested in your accessories that you have included with the amp, all those small boards that do stuff. I will be starting a new amp project myself probably after the new year, maybe sooner. So I am really interested in the details of how well all those extras actually work out.

    I have built many amps over the years both tube and SS. But these new NXP/Ampleon transistors have my highest interest now. They have some capabilities that seem to blow away the older MRF Motorola and Toshiba transistors including very low $/watt. I have many sets of boards for about a 1/2 dozen of the NXP devices. I haven't made up my mind yet which one to build first. Pictured is the board for the BLF188. I plan on doing a very detailed write up on the construction and testing but it won't be on QRZ, it will be on my own website just for the project. I will construct a one board and a 2 board amp for 1kw and 2kw amps and maybe some other unique capability amps.

    Please keep us informed on your present amp project.

    Attached Files:

    AF6LJ likes this.
  3. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Hello RICHS,

    Fear not, I am actively working on my amplifier and will be posting an update soon. Most of the support boards in my amplifier came from EB104.ru. I highly recommend his products.


    AF6LJ likes this.
  4. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    Looking forward to the update. :)
  5. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Hello All,

    I am so close to getting my amplifier 100% operation but "no cigar" as yet.

    I changed the bias control switch (always applied to the PA board verses only applied to the PA board when the transmit button is pushed) into an amplifier standby switch. Now I have no problems with the LDG automatic antenna tuner doing it's thing when I manually place my amplifier in the standby mode. My only problem now is to have my transceiver control that operation when I press the Tune button on the Icom IC-7300. I designed a remotely controlled Standby circuit based on the assumption that when a tune request is not activated the input to my new little interface board is an open circuit. Turns out that Icom has +3.2 volts DC sitting on the Tune line to the LDG antenna tuner and, in turn, to the base of the switching transistor that actives the standby circuit in my amp turning it partially on. The net effect is my amplifier is always in standby mode. I have to play with my remote control standby circuit a bit but I feel like I am almost there.

    It is late or me here on the East Coast and time to put my head down but I wanted to give you a quick up date.

    AF6LJ likes this.
  6. N1OOQ

    N1OOQ Ham Member QRZ Page

    I am amazed at your perseverance, Ripley.
    AF6LJ likes this.
  7. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Hi Thomas,

    I have come so far and am at the point that the solution to this one last issue is almost within reach that I can't give up now. Besides, to put things into perspective, if I was build another R/C scale model for competition purposes I would only be half way through year one of a three year project. Talk about perseverance consider working on the same project every week night for one and half to two hours plus another 5 or so hours every weekend for three years until your creation is completed. That takes dogged determination to see your creation through to the end.

    Not much to report this evening. I am working everyday now at the Radio Museum for at least the next two weeks so I can only spend about an hour our two in the evening working on the amplifier. Tonight I basically undid what I created the night before.

    AF6LJ likes this.
  8. N1OOQ

    N1OOQ Ham Member QRZ Page

    Hey Ripley,
    Tks for the heads-up on the "lens tinting paint". Just what I needed for a minor project... putting a cheapo Chinese freq counter PCB in a box. See... I learned something in this thread! They sure don't give the stuff away, though.
  9. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Hi Thomas,

    I don't remember what I payed for the tinting paint that I bought but at this point I don't much care. It's only money. :rolleyes:

    I moved a step forward this evening. I now can initiate a tune command from my transceiver, the linear amp will go into standby mode, and the LDG automatic antenna tuner will complete a tuning cycle without going into protection mode or generating some other error. That is a good thing. However, the transceiver keeps sending out a carrier continuously unless I push the TUNE button again on my Icom IC-7300 to stop it. In fact it is even more interesting than that. I request a tune cycle to start from either the transceiver or the LDG antenna tuner, The KEY line that runs from the antenna tuner to my transceiver and linear amplifier goes low causing the transceiver to send out a carrier and inhibiting the SEND line within the linear amplifier so that the antenna relay stays de-energized during this operation. The tune cycle is now complete but my transceiver is still transmitting a carrier so the IC-7300 thinks that I want to transmit and it energizes the antenna relay. My output power goes from 30 watts to 500 watts. Not a good thing. :(

    If I push the standby button on my linear to manual short the base of the switching transistor to ground with the KEY cable connected to the amplifier the same behavior is exhibited. Pushing the standby button again to remove the short only causes the amplifier to go from standby output power to full power. The only way to stop the transceiver from transmitting is to touch the TUNE button on the radio again.

    Hmmmm. My simple solution to insert a switching transistor between the relay coil of my bias/antenna driver relay and the SEND line to my Icom transceiver almost works but not quite. I think I might have to add another layer of isolation between the KEY line coming from LDG antenna tuner to my amplifier.

    More head scratching to do.

  10. KD8UYQ

    KD8UYQ Ham Member QRZ Page

    Hello folks,

    Well, I think I got it figured out.

    It took some fiddling with the switching transistor circuit for the antenna relay but now when I press the TUNE button on either the LDG automatic antenna tuner or my Icom 7300, the linear goes into standby mode, the antenna tuner matches the transceiver to the antenna, and when it is done takes the amplifier out of standby and puts it one line. No more High Power/SWR errors from the LDG AT-1000ProII. The antenna tuning process now works like a dream.

    That little exercise was resolved on Sunday so for the frosting on the cake I decided to add an LED that would light when the amplifier was in standby mode. Such a simple thing which turned out to be a major "Pain in the Bee-Hinder" to get working properly. The LED is driven from the circuit that controls when the amplifier goes into standby mode but due to several factors I couldn't get the LED to light only when I pushed the STANDBY button on the amp or when I pushed the TUNE button on the IC-7300. The LED wanted to illuminate whenever I was transmitting as well. Several pencil and doodle pad meetings with my Elemer at the Radio Museum later and we came up with an idea that I finally got working this evening.


    Now all I have to do is take the components from the bread board and mount them on the bias/antenna relay control board.



    Once I get the LED circuit built and installed in my amplifier I will report back with a schematic that details out what was done to make everything work.

    The best news is I don't have to chase any more dark magic RF issues with this project anymore.

    WA9WVX, AF6LJ and N1OOQ like this.

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