TX-only modification on commercial WiFi booster

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  • Please take a look to the pictures The first one shows the "8 Watt" ( in real ~ 3 Watt) AMP with ugly aircondition - but it works fine.


    The second one shows the 4 Watt (~ 2 Watt) Amp. Both amp having the same modification.

  • it's free but requires registration:

    "If it is your first time you visit this site, you must first create an account. Click here to begin the registration of the account; it is free to create the account. If you want to know why you should create the account then click here."


    free "subscription" only limits the number of files you can download daily.

    Hi Claudio


    You are right, but the control characters are not readable :thumbdown:

  • Hi Guys,


    I tried to modify the 8watt version today. With the constant tx mod and about 350mW input i only managed to get 29dbm out. I took out both diode switches and now i'm up to 30dbm with 200mW drive. It's pulling 1.4 amp in tx and 350mA in standby.


    Any idea where the power is going ?


    73 Jan


  • On6zg: the biggest part of the power is converted into heat. Here you can see an infrared picture of the EP-AB003 amplifier close to full load. At full load the temperature at the hotspots (white) rose to 75 degrees C and stayed there.


    Best 73


    Holger ‚Geri‘, DK8KW

  • DL5RDI hi Johannes. Increasing the power didn't result in higher output. So it should be at saturation.

    Both transistors seem to be working and pulling current. I read about some filtering that could be removed in de the output?


    73 jan

  • On6zg Hello Jan, in my PA there are only a few parts for matching the output

    (see image below), but no real filtering. Maybe the matching can be optimised

    for 2400 MHz (but shouldn't be to bad in original because it's the lower end

    of WLAN frequencies.

    (A friend of mine even measured 35dBm in an unmodified PA of this type).


    73 de Johannes



  • DK8KW

    Thank you for this nice IR-Image. Yes the transistors get hot, but no relevant temperature in the output-matching-section, that means, that there seems not to be a relevant loss of RF converted to heat. (I.e. seems to be not the source of the "Lost Watts")


    73 de Johannes

  • I have the 4W version of the PAs.

    Seems like the mod needed for this needs really very still hands..

    And a very nice solder tip hi hi.. Dont have any of them..



    Maybe it might be easier to build the vk2xax solution at vklogger, a diode , a resistor and 12v

    First question.. what kind of diode should i use,



    Second, is there any easier way that i can try???




    PS: Just noticed Alex's note.. So shorting pin 4-5 will be enough I suppose.

  • ta2nc


    Hello,

    reading your post I think you mix a few different things.


    1. The shorting of pin 4-5 wil set the PA in a permanent TX mode. This will not add any mW to the output power. If your drive level is >2dBm this modification is not necesseray and you will not notice any difference.


    2. VK2XAX made 2 modifications. These modifications are only useful if you use the PA not only for TX (like for QO-100) but also for RX (e.g. terrestrial 2way QSOs in 2,3 GHz).

    (Removing the input TX/RX switching and replacing it with two SMA-jacks; one for the TX path and one for the RX path - the output switching is not modified).

    The second modification is also only useful in a 2.3GHz 2way QSO situation. Here he modified the RF-Vox to a "hard" PTT-switch. (This is also not needed in QO-100).


    If you have enough drive level (about 200mW) none of the above modifications give you any advantage.


    The only modification rising the output power in this situation is to bridge the output-switching diode. (and perhaps to add the small wire for a little bit less voltage drop inside the PA).


    73 de Johannes

  • Hello and thanks for explaination.

    I am planning to use this pa for ssb on qo-100 with hmc213 + 2x spf5189

    which i guess gives enough power to drive the PA

    We are not allowed to use 13 cm band in TA so, I wont need two-way communication for now.

    Isn't this mod needed for SSB communications? Or do you think it is fast enough to handle tx/rx switching during ssb modulation??

    For now putting a little drop of solder between pin4-5 put the PA on permanent TX state..

    Not much left to do to be qrv on qo-100

    OCXO Checked.

    ADF4351 Checked.

    Antenna Checked..

    PA Checked..

    filters and lnas checked


    only need to find a stable way to limit my ft847 to 10 dB for mixer

  • Quote

    Isn't this mod needed for SSB communications? Or do you think it is fast enough to handle tx/rx switching during ssb modulation??

    Hello,


    I do not only think it is fast enough to handle tx/rx switching in SSB - i know it for sure ;-)


    73 de Johannes

  • Hello together,


    I can comfirm what DL5RDI said: the permanent TX-modification is neither necessary for SSB nor for CW. In my view the only valid reason to do this modification is when you want to reduce the power for whatever reason, for example to test low-power (below noise floor) data communication. As the HF-VOX switches only above a certain input power (in the range of 5 dBm), you can further reduce the input power only if you did this modification.


    From my experience I can also confirm that this amplifier can produce around 2 to 3 Watts, not much more. For a brief moment I got about 5 Watt output, but not for long, and not reproducable (unmodified PA).



    Best 73


    Holger ‚Geri‘, DK8KW