What TX amplifier do you plan to use?

  • I don't think I am brave enough to try that module. Although it is multistage with a lot of gan, I don't think I am experienced enough to try to snowflake a multistage amplifier at this point- and the inbuilt doherty worries me as I hate not knowing what is going on in a chip - I can't adjust the internal lines!


    I decided to opt for the dual MRF7S21110HS board that he has on offer. Probably a little less power - and a lot less gain but hopefully easier to work on!

  • I was looking at the BLD6G22L-50 datasheet


    which looked like the 90 degree shifts were built in to the BLD. I assumed the -150 was just a higher rated version.


    To be honest - I'm out of my depth here - this isn't my area of expertise so I'm just guessing - that's what I like about this hobby - always something new to find out about.

  • I took the pin numbers on the diagram to match up with the pins shown on the device


    This is just curiosity for me as I have bought a different board now!


    Also:

    The BLD6G22L-50 and BLD22LS-50 incorporate a fully integrated Doherty solution using Ampleon’s state of the art GEN6 LDMOS technology. This device is perfectly suited for CDMA base station applications at frequencies from 2110 MHz to 2170 MHz. The main and peak device, input splitter and output combiner are integrated in a single package. This package consists of one gate and drain lead and two extra leads of which one is used for biasing the peak amplifier and the other is not connected. It only requires the proper input/output match and bias setting as with a normal class-AB transistor.

  • Thats a relief, I wish I'd bought one now!


    I'm sorry if I caused you concern - I just assumed the BLD6G22L-150 and BLD6G22L-50 would have been similar devices given the both have the D for doherty!


    The only information I could find for the -150 was as below - so the Idq you measured of 1340 looks to be in the right region. Apparently the module was rated at 60W (linear) in the sales literature.


  • DB8TF Florian, the Doherty concept makes that when the 'main' amp is above saturation, a second (or 'peak') amp 'helps'.


    Mostly the main amp part is in class AB and the peak amp in class C.


    So, the overall efficiency is better compared to a balanced ('push pull') amp.


    Say AB has 60% efficiency and C has 80% efficiency (modern LDMOS can have these efficiencies) means that (push pull) 0.4 + 0.4 = 0.8 / 2 = 40% is dissipated, whereas

    (ideally) in a Doherty setup 0.4 + 0.2 = 0.6 / 2 = 30% is dissipated (so 25% less).


    In contrast to a push pull, where the phase difference between the two halves is 180°, the phase difference in a Doherty amp is 90°.


    Assume the input splitter of your amp is of a 'rat race' type and that 90° ports are

    selected, the output combiner must also have this 90° phase shift (but then in the opposite direction).


    Looking at the output circuit, you marked a 90° delay line from which I strongly conclude it is a Doherty setup (!)

  • Sure! In the picture you'll see my homemade "connectors" using dual row, 2mm spaced pin array. Covered with hot melt glue. Original SMP output was located on the right of the circulator, ugly replacement SMA soldered instead. :) Could not find a SMP mating connector so I let it go.

    Hi,


    have you some information about modification and power supply for this amp ?

    Thank you.


    73 Alex

  • Tu, giving up on this amplifier...


    regards.


    73

  • I received my amp from poland on Thursday and just managed to put it on a heatsink to test it.


    I got the 'RF linear amplifier with - 2x MRF7S21110HS - 2,2GHz' from bisonelectronics for £29.65 +£4.24 postage


    I did snowflake it a little putting thicker input lines to improve the match - but then took them off to test it in its bare state properly so I could get a baseline for improvements.


    I connected it up to 28V and set both bias to 1100mA via a pair of simple regulators and then adjusted the two input trimmer capacitors for a reasonable SWR ( about 1.7:1) and then started measuring. It's a bit of a fiddle to adjust the input caps as they seem to work in opposite directions. With a small signal in (100mW) I adjusted them a little further so the drain currents on both were about balanced - its difficult to match properly when there is a zinger in the input dumping any mismatch.


    With my capacitor settings I got a 1:1.2 match @2.2GHz , rising to 4:1 at 2.3GHz and back down to 1.7:1@2.4GHz


    Much to my surprise these are the results I got:


    Gain 13dB @ 40W out

    Efficiency at 40W 28%


    I have no idea what the max CW power output is as it got up to 80W before I realised that I was in danger of blowing up my dummy load which is only rated at 50W and ought to stop before I damaged something.


    Excuse the mess in the photo - I only had a couple of hours free so I thought I'd just rush in and clear a few inches of desk space to give it a quick try.




    So it would seem this runs quite nicely without any snowflaking required. I've bought another one in case I blow this one up while testing.


    Edit: The output combiner is only rated at 105/145W and whilst the p1dB of each device is 110W I suspect it would blow up if I pushed it any harder than 80W. I cooled it with 2x 10cm fans and the temperature stayed about 46 degrees when testing.