Posts by DK4FT

    tnx to all...


    I always connect input and load before adding the power supply.


    I received some hints to follow up and will do as soon my time permits.

    First one received more than once is to change to manual Bias Voltage instead of the build in automatic one...


    Keep you informed....

    Update: Received the Power Supply for the Nokia Amp and killed the FETs?!?


    After first connection the Idle Current dropped from 3,2A to 1,7.

    I doublechecked this with the lab supply, which confirmed this.

    At the second try it dropped to few milli Amps :-(


    It seems the supply fried my FETs, as Voltages on the FETs are still fine...


    I check polarity and voltage = all fine.

    With the Oszi I checked for Transients, there were some on top of the DC, but only abt. 20mV.

    So I have no Idea why the supply killed the Amp, but it happened.


    Any Idea what went wrong?

    I seem to miss some detail at the moment :-(

    Just tested the Amp with my Lab Power Supply.


    Did

    - the Doherty Change to enable peak FET permanently,

    - change input sockets to SMA

    - change Output

    - remove Isolator/Circulator at the output,

    nothing else, so far.


    IDQ is 3,2 A @28V.

    The Amp has abt. 48dB Gain on 2,4 GHz, not too bad.

    If the meassured gain is correct, there is no need for snowflaking...


    Due to my Lab Supply I am able to produce only 2,5 W at the moment, but the Amp is getting really hot with both End FETs enabled even in idle. (need a fan...)


    Now I am wating for the big supply (welding Source ;-) )


    Thanks Roland for the picture....

    Here is my one....

    G3XOU Thanks for the Bias Cirquit.


    DM5RM Good hints from your side.


    I received my Nokia Amp from Bisonelectronics and startet to rework the input/output (attached directly semi-rigid Cable with SMA-Connector instead of the very specific existing ones). Biases I will leave as it is for the moment and ordered this Supply to have enough power:

    https://www.ebay.de/itm/1PC-Po…ksid=p2057872.m2749.l2649



    Roland, could you help me with the following two questions, please:

    1. Did you change the Doherty Cirquit of the peak amp like Flo?

    2. Could you upload a photo of the copper piece on the C?



    73 de

    Alex, DK4FT

    DB8TF thanks for the pioneer work…


    I ordered same Nokia Amp and checking the different posts as a preparation until the board arrives. I read the thread several times and I seem to miss some parts of the puzzle...


    Here what I got - StepbyStep


    1. remove and bridge the first stage (D100 = PreAmp?) and both filters (W100/W101) and Circulator

    2. change IDq for Driver- and End-Stage

    3. change Doherty Cirquit to enable 2nd EndFet

    4. put a Anaren Xinger in the output and cut the 90°combiner lines on the board

    5. Start Optimization/SnowFlaking as shown in the pictures with low Power


    (Probably I will interrupt connections to the Peak Amp and drop step 3/4, if one EndFET will give me enough power)


    Could you give me some details about following mods, please:


    1. IDq - you setup an IDq of 2A for the whole amp (incl. pre-Amp) or per End FET?

    2. you injected the BIAS from external 12v, could you post the circuit diagram?


    vy 73 de

    Alex, DK4FT

    Hi all,


    after the initial tests my 20W booster seems to be dead :-(

    I am still testing if the first or final stage is affected, only 10 dB gain of the unit is left...


    Did someone else erperience similar issues?

    As the implemented amplifier chips are chinese parts, does someone got an idea where to get spare parts?

    (I know the downside of chinese modules...)


    vy 73 de

    Alex