What TX amplifier do you plan to use?

  • Why were the notes removed ?
    is this commercial use ?
    i was just about to start modifying the amp


    A eBay seller has linked to the modifications here without asking for permission first and earns a lot money selling his amps.

    A lot of time on my side was invested in this modification and it was only intended for Ham use, without making money with that.

    I have observed that for many months now and won't support that any longer.

    There are still useful infos from other OMs available in this forum.

    73s DB8TF

  • I did the snowflaking tonight to my Nokia-Siemens PA and after I mounted everything very nicely together, the lid was closed and I fired everything up with a very gentle drive of my Pluto + CN047 I was wondering about too low output as compared to the unmodified tests made before.

    Driving the drive up very much I got something like 10-15W out at best.

    Much less than in the previous unmodified state.

    I then measured the IDq of the 28V supply and instead of seeing the usual nominal 1.9A that I saw before now there is only around 250mA oscilating sometimes up to 350mA (at least its moving slowly up/down and is not absolutely steady)

    Looks like I have a faulty bias regulation like many other have reported here? I wonder why this happened so suddenly.

    (but seems also a similar "sudden death" as the others here who experienced the same)

    I need to see if I can locate the faulty R and/or C and temporarily fix it....(any hints on how to locate them?)

    Or discard it and just use external biasing...which is perhaps the best solution.


  • Hello friends,

    so far no sucess in spotting faulty C's or R's (3.7kOhm and 37kOhm feeding the two BLD6G22L-150BN/2 bias regulator ICs and also 3.7kOhm feeding the 2nd stage regulator). Those values are much different than the 150ohms that Dave G3XOU reported here (Post #190). I am not sure what the nominal values should actually be.

    C's at least do not seem to be short circuited, but since its not recommended to power it up with an open lid I am not sure how to do further measurements in e.g. powered state or using thermal spray as someone sugessted here in an old post?

    Did someone successfully added external biasing to the PA variant with BLD6G22L-150BN/2?

    The BLF8G22LS-160BV version uses only one single bias feeding line per device, which makes it easy.

    The -150 version however since it is a double package would require feeding at four points of the final stages.

    The "inner" two points on the PCB seem to be fed from an inner PCB layer coming from the bias circuit.

    Did someone already try to locate some convenient common point per device in the area of the biasing circuit where to interrupt original and connect external biasing for the -150 device PCB layout and is willing to share insights?

    The -160 seems to be soo much easier to feed with external Bias in this respect without having to think much about routing of the wires ec., hi...

    73, Oscar

  • Thanks Heiner, but not really, since this is a totally different PA (this is the "small" Polish PA) but Bias circuit seems to have some similarities....also this one is a single package (more similar to the -160 devices) and not a dual package (like the -150 devices)...

    Will continue searching.

    73, de Oscar

  • My Amplifier is repaired in the meantime. It was the faulty resistors that are feeding into the bias circuit with 28V...

    Mine were 3.7kohm and 37kohms.....now replaced all by 11 ohms and works perfectly.

    In the -160 version they use two in parallel (instead of only one in the -150 LDMOS version).

    Maybe a good mod for -150 type users to solder in two 22 ohms in parallel.

    Maybe more durable, hi hi...

    73, Oscar

  • Thanks Sandor. Highly appreciated! (WhatsApp was not showing any User name on my phone, so I was not aware it was you)...

    In parallel I've also got those 2x22 ohms measured by Arved M0KDS....(for the -160 version) to whom I also send my thanks...

    73 and thanks for all the help

  • Anyone run into this issue with the SP8XXN / SP5XMU UMTS amplifiers?

    [Blocked Image: https://i.imgur.com/yS9kmWI.jpg]

    - it got half a watt for a couple of seconds

    - there's a known good 3GHz dummy load on the output

    - it's bolted solidly to an aluminium heatsink, heat transfer compound below it

    - it's modified per the PDF

    - the case was bolted on

    I suppose the other question is, anyone know what value / type those two capacitors were?

  • not if you have solved the problem an attempt, the two condensaroti to see to measure the value and you can put back the same I do not think it is not a different value and a drop in RF

    73 ik1hgi Tony

  • Hi All,

    This weekend I had my 2x BLD6G22L 150N/2 Nokia amps finally transmitting DATV to QO100 succesfully. Where the PA draws some 1.75A without RF and a little above 10A with RF. After 1 hour of playing I noticed that the power went up and down (sometimes 10A supply and sometimes 5A and also the stand by current (no rf) seemed to switch between 1.75 and 3A. checked some bias resistors that where mentioned to be failing in other threads but cannot find anything wrong. Any suggestions what is happening here?