What TX amplifier do you plan to use?

  • Sorry, I was not thinking to the end as a lambda/w wire would have been around 7,5 cm!!
    It sure is a nice amplifier.
    I have bought a few PCBs of TELRAD amplifiers, from their Breeze Compact 3000 equipment, see #320.
    They do not need any snowflaking and are good for 20W DATV. I am using it as driver, but friends are using them also for linear NB amplifiers. Efficiency is quite bad using the Idq from data sheets, so I will follow your hint and try reduced values.
    73's

    Gerhard

  • DB8TF, I get about 70W out of the bison PA. I did the snowflaking, but not changed the bias currents, just provided 28V.


    Now 90 vs 70 isnt much but stil interesting to explore. When I increase input more no further increase in output.


    You bias mods may give that 20W extra.


    PA is very stable I need to say, and does not get hot.


    Henk

  • Yesterday I fired up mine (BLD6G22L-150BN2 variant) for the first time without smoke, hi hi.

    I just tried it first in unmodified way. (only replaced the Input and output connectors, nothing else so far)


    All Bias currents looked just fine as described here and (so far) no problems with unstable internal bias circuits.

    But this could still happen, like others have experienced...


    The amp produced nice strong signals, hi hi (I drove it up to approx. 8A at 28V, but cannot check output power right now).

    However I noticed that audio was not sounding very clean as with my other amps (SG Labs or PA3AXA), a bit rough, specially when underdriving the amp for lower power output. Could this be related to the Doherty mode or to the Bias being optimised for contiunous data modes?


    Regarding snowflaking I need to upgrade my measurement devices first, so I am not really ready for that yet (or at least have it calibrated against a good reference).


    I wonder if the modification of the Doherty circuit is worth it? And perhaps also externally biasing it?


    DB8TF In an older post you decribed your biasing circuit, but would be great if you could draw it on a piece of paper and post it here for more clarity?


    Someone also mentioned (I think it was Sandor DM4DS on some other channel) that the 1st stage amp presents a total system limitation on 2.4GHz and is partially responsible for the -10dB amplification many people see on 2.4 vs. the original design frequency.

    Can someone confirm this is the case?


    So one of my next first things would be to remove it and do a direct connection to the second stage (similar as in YO5ER photo and others). It seems to me there are still some hams playing with this amp type so all hints published here could help others. Thanks for all the great posts so far.


    73, Oscar

  • OK dzięki jak by ktoś miał link do strony polskiej to bym poprosił.Tylko będzie mały problem bo do tego wzmacniacza trzeba dać minimalna moc 2 W a z D X Patrola wychodzi 250 MW czyli pomiędzy nimi musi być jakiś inny wzmacniacz 2 W .Ja mam takie pytanie jakby tam dał wzmacniacz 4 W to przesteruje moją modulacje czy zablokuje duży wzmacniacz.

  • OK dzięki jak by ktoś miał link do strony polskiej to bym poprosił.Tylko będzie mały problem bo do tego wzmacniacza trzeba dać minimalna moc 2 W a z D X Patrola wychodzi 250 MW czyli pomiędzy nimi musi być jakiś inny wzmacniacz 2 W .Ja mam takie pytanie jakby tam dał wzmacniacz 4 W to przesteruje moją modulacje czy zablokuje duży wzmacniacz.

    Please English (or German) only...


    73 de Frank PH2M

  • OK, thanks, if somebody would have a link to the Polish website, I would ask. There will only be a small problem because you have to give a minimum power of 2 W to this amplifier and 250 MW comes out of the D X Patrol, so there has to be some other 2 W amplifier between them. I have a question as if I would give a 4 W amplifier there, it will override my modulation or block the big one.

  • Hallo all...


    some short update...


    got a delivery of the small LM317 modules ... which can be modified with a little work (more than i have thought)


    what to do...


    - remove the trimmer resistor

    - cut out the ground pads on the upper side of pcb

    - make an "island" for the other 2 pins of the trimmer on the lower side of pcb

    - resolder the trimmer

    - add 820R (smd) and 100nF (smd)


    pictures and diagram of the modified pcb attached...


    73 & have fun with modification of amplifiers

    Michael dg0opk

  • Hi all...


    some work for the next weekend... ?


    ANDREW MW7IC2240 MK2 ...maybe running on 12V for a new portable setup....;)

    BUT NOT TESTET so lets see.... (look update)


    73 de dg0opk


    UPDATE: 1.may 2020

    -------------------------------

    first test are done, i got the following parameters with 12V DC input and setting the idle current overall to 1.07A@12V
    ( around 550mA @24V)


    Rf-Drive Idc(A) @ 12V Pout effienciency overall (with DC/DC)

    -------------------------------------------------------------------------------------------------------------------------

    off 1.07

    -3dBm 1.16 26.8dBm low

    2dBm 1.38 31.7dBm 8.8%

    7dBm 2.03 36.5dBm 18%

    10dBm 2.6 38.3dBm 21%

    12dBm 3.48 41dBm 29.7%

    13.5dBm 4.37 42dBm 29.8%

    16.5dBm 5.67 43dBm 29%

    18.8dBm 6.4 43.4dBm 28.5% (SATURATION)


    amp is linear nearly upto max.15W, Pout max =22W @ 24V


    NOTE: you need some additional CAPACITORS because of the DC/DC supply...


    this PROJECT is nearly finshed now....


    73 de Michael dg0opk