Driver PA up to 1W

  • Hi Roberto,

    Schematic is very simple. As per datasheet do not drive more than 5 mW at the input (50 ohm), put 12 to 28 Volts on pins 2 and 3 depending on the output you want and output is at pin 4 (50 Ohm).

    See the photograph for the decoupling of the powerlines. Take several values of capacitors, I did 22pf, 5000pf and 100nf. Any series inductor from the junkbox will do.

    Take attention to get a good ground connection, remember it is 2.4GHz...

    Hi I received the mhl21336 from ebay sorry, am I going to know the two large capacitors you see in the value of the photo? and the small ones I think are 22 pf, and the two value inductor?

    tnx Roberto

  • Hallo,

    very interesting to me also. I own this board and can confirm no gain at 2,4 GHz. Maximum is about 1 GHz. The modification is similar to the datasheet. So, thanks to DK5DN for publishing, I will try it and report. Last question, what is about the feed choke.

    I think it is unmodified yet?


  • Hallo,
    the modification works.

    First grafic shows the 1W PA unmodified and another wide band amp which is ok. S21 is measured against 19 dB attenuators.

    The second grafic shows the modified 1W PA. The gain maximum is shifted to S-Band.

    Don't be confused about the ripple. It is amateur equipment. :)


  • Hi.

    Things are progressing slowly with my homebrew upconverter.
    I'm about to programme the ADF4351 for a frequency of 1967.5MHz.
    The Analog Devices software has generated some info for the 6 registers but there are many 'options'.

    Does anyone know if the following settings look reasonable? Just trying to avoid a local oscillator with poor performance.

    Thanks David

  • @G0MRF Depends what reasonable is ; -) You did not specify the R-divider so your PFD is 10 MHz , which forces the whole thing into FRAC-N mode.

    First decide if you want FRAC or INTEGER mode and then derive the PFD from it.

    As a rule of thumb, for lowest phase noise your PFD has to be as high as possible

    using INTEGER mode. But these chips have much sophisticated options to improve P/N-performance in FRAC-N mode.

    I use 500 kHz PFD for 1967.5 MHz , so my R-divider with 10 MHz reference is 20 and I am a fan of the 4/5 prescaler mode (iirc it produced a better signal on the analyser).

    Output here is always 5 dBm (although I never reached 5 dBm with my cheap Chinese boards)

    Depending on what ADF435x board you have, there are a few routes to Rome and you've to experiment with it (in conjunction with the loop filter) and look on the spectrum analyser for the best spectral impact. E.g. you can experiment with the charge pump current etc.

  • A pity to read your experience. Normally this module does not give any problems. Essential however is a good grounding,

    I used thin copper foil under module as well as the board. see my earlier photo.

    My module easily outputs 2.5 Watts without overdriving the input.

    I experimented with a trimmer at output, but that is really not necessary.

    73 de Cor

  • Hi I built the cun mhl21336 amplifier but depending on the length of the output cable the resonance changes, it doesn't give me power because it should be along the ut141 cable

    Hi I built the cun mhl21336 amplifier but depending on the length of the output cable the resonance changes, it doesn't give me power because it should be along the ut141 cable

    thanks, the 5000 pf capacitors I used 4700 and two vk200 inductors for power supply should not be critical



  • Hello Roberto,

    If the module is not oscillating, the decoupling will be OK..

    Do you have placed via's in the connection board to ensure the top copper is connected to the ground?

    I did solder copper tape around the edges and placed copper under both the connection board and module.

    Maybe you can add a copper strip between the module screw at the output side and the connection board.