What TX amplifier do you plan to use?

  • Just finished modifying another UMTS PA (BLF8G22LS-160BV) this time for OM DM4DS Sandor.

    Max power easy over 100W but as my power attenuator gets very hot i stopped @ 100W (320mW drive).

    Signal looks clean on spectrum analyzer.

    I attached some pictures from the testbench and part of the used equipment.

    73s DB8TF

  • Hi great, I see you use the Daiwa power meter but the power returned 2.4ghz?


  • iw5bsf: the power meter is a usual "Daiwa NS-660P" cross-needle power/swr meter. This goes to max 150Mhz.

    But i use a external (and very rare!) measuring head "Daiwa U-66S2" which works from 1,2 to 2,5GHz with 1,5/15/150W power ranges.

    73s DB8TF

  • Update:

    the amp burned all PCB trace behind the combiner after 30 seconds on DATV with ~35W.

    Flo tried to repair it but was not able to do. Now it´s running only on 1 Transistor and running ~35W with very bad efficency.

    I modified myself another one and this one is doing 150W @ 28V @ 16A without any problems.



    Old Post


    Today i got the PA from DB8TF - Flo back . Amazing.

    Pictures #225

    First QSO was with Flo and its fantastic. For SSB it´s quick too much power with my 1.2m dish. I think it´s easy to trigger LeiLA , we didn´t!

    In KG-STV super clear Eye-diagram.

    After i figured out how to stream the small ksyms, i´m good for some DATV :)

    Thanks again Flo. Surprise follows!

  • Hi DB8TF,

    Great work!

    Could you please share what are the changes you have done to the board?

    I own the same PA unit, however I’m trying to figure out what changes need to be done.

    I see that you have replaced the input connector with SMA (BTW, what is the original connector?)

    And that the circulator was replaced with a N-type. There are few copper patches (I assume for better matching). What changes are not so obvious? Is the amplifier still working as a Doherty one?



  • 4Z5YR: i took the following steps (not in full detail)

    removed ALL filters/isolators/circulators from the PCB and made straight connections

    removed the first stage because the driving pwr was about 100-800mW so no first amp needed

    modified the finals from doherty to manual IDq setting (the automatic IDq on the second driver was working ok so i leave it)

    installed a SMA input and N output connector where the output circulator was.

    carried out a lot of snowflaking and resizing pads on the PCB to get best gain (takes long because you have to remove and

    reinstall the cover after each try)

    73s DB8TF

  • Hi, did you measure current consuption of PA module with 100W output? How many Amperes did you get?


  • I didn't measure the current but you can ask DM4DS who now has this PA in use.

    Maybe he can measure it for you.

    My SPSU is limited to 15A so i assume the current @100W was lower.

    73 DB8TF

  • DB8TF and DM4DS

    Thank you both for information. After modifying my the same unit takes about 11A with 28V from PSU. With 100mW input power, output is about 100W (may be some more). I'm using it for WB operation. With 0.85m offset dish and 333kb/s signal, amplifier provides 9dB over noise on web monitor.