HOME MADE Solid State HF Amplifier with 16 mrf150

1. Specifications
Frequency : 1.8 ~ 30 MHz all amateur bands including WARC bands Mode : SSB, CW, RTTY
RF Drive : 85W typ. (100W max.) Output Power : 2.4 kW (typ.)
Matching Transceivers for Auto Band Decoder : Most ICOM, Yaesu, Kenwood ,Auto sampling rf in , Manual
Drain Voltage : 42 V
Drain Current : 100 A max.
Input Impedance : 50 Ohm (unbalanced)
Output Impedance : 50 Ohm (unbalanced)
Final Transistor : MRF150 x 16 Circuit : Class AB push-pull
Cooling Method : Forced Air Cooling
MPU : PIC 16F877
Reflected Power Pr 300W
Input/Output Connectors : UHF SO-239 with low loss Teflon insulator
AC Power : AC 240 V (200/220/230/250 V) 25A max. AC Consumption : 4.5 kVA max. when TX
Dimension : 490 x 190 x 380 mm (W x H x D)
Weight : Approx. 12 kgs.
RCA Plug (Stereo Type Pair Cable) x 2 Band Decoder



2. Features

2-1 Our solid-state broadband design engineers worked to make the MOS16150, the lightest 2.4 kW HF amplifier. This world-class compact 2.4kW HF amplifier is the easiest to handle and operate.

2-2 The amplifier is equipped with a newly developed band decoder. The amplifier�s decoder changes bands automatically as the data signal is received from the associated HF transceiver�s frequency bands.

2-3 The amplifier�s main PA section includes 16 high power MOS FET MRF150, resulting in 2.4 kW (SSB max.). The amplifier�s broadband characteristics require no further tuning.

2-4 The amplifier allows operation in full break-in CW mode due to the use of the amplifier�s high- speed antenna relays (made by Panasonic/Matsushita).

2-5 With the unique duct structure design and the powerful blower fan, the aluminum heat sink block for RF PA module (and other components), are effectively cooled. The fan�s quiet operation.

2-6 The amp utilizes an advanced 8 bit MPU (microprocessor) to run the various high speed protection circuits such as overdrive, high antenna SWR, DC overvoltage, band miss-set etc.
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    Automatic band change based on rf input or by cable for yaesu and icom RTX
    Microprocessor assisted for band change and protetction : ros , temperature , fan speed
    Output circuit revised , the original EB104 do not perform ok in all band , efficiency improved



    The experience with the EB 104 started about 2 years ago; the first test have been done only with one module, the results were not very good.

    The results at 50V were:
    1) very low performance
    2) the C11 capacitor was used to optimize the 160 Mt band but with a degrade in the 10 mt. band and vice-versa
    3)there was too much heat to dissipate
    4)in presence of VSWR the mos-fet were at very high risk of burning
    The T3 trransformer were not matching correctly the impedance.

    After that we lower the voltage at 40V and we found that the performance was much better
    The output power stays almost the same with the same current and this confirm that there were impedance matching problems.
    We still had the problem to cover all the bands.
    After having redesigned the T3 transformer, we achieved the full coverage at full power of the entire band starting at 160 mt till to 10 mt. and we could bring the  voltage at 42V.
    the performance  now at full power is about 55% while at lower power it drops till 30%.
    For a use with continuous carrier with a lower power it is advisable to lower the voltage at around 30V using the amplifier at maximum power that in this case will be around 350W and the performance around 65%.
    At 42V when at 350W, the performance is 40% and the heat is similar that the one at full power
    At this point we decided to switch to the configuration composed by 2 modules coupled through the PSC-2 coupler by Communication Concept.
    The output power was the same that using only one module, basically the system was not working.
    After various tests without any success, we decided to test the PSC-2 with the network analyzer (HP 8753C) and we immediately found the evidence of why the system was not working: the output impedance of the PSC-2 was 11 ohms instead of 50 ohms.
    I will post pictures of the measurements taken with the network analyzer.
    At this point  we see 2 possibilities;
    1) My PSC-2 has been built in a bad way (it can happen)
    2) The project of this coupler is wrong

    With the network analyzer we have made some changes in the coupler so tha we have obtained 50 ohms output impedance.
    Once that we have tested the coupler after the changes, we immediately got the power doubled; we now have around 1200W all over all the bands.
    From there we passed to a 4 module configuration; this time the PSC-4 was working perfectly and we immediately got 2400W all over the bands.

    The PSC-4 coupler also if the technical specifications are for lower power, performs well in SSB. It is clear that it cannot be used for continuos carrier because it becomes too hot in a very short time.
    This coupler is cooled by the flux of the air.

    With the amplifier powered at 42 volts and current around 90 amps in many cases the amplifier (because of mistakes) has suffere SWR very high close to infinite; some times still by mistake we have activate the transmission without beeing connected to the antenna or with the filter selected in the wrong band;
    it never happened a problem, no mos-fet burned (it only happened when we tested one module with 50 volts)

    We have designed a microprocessor program that handles all the protections; we inhibit the amplifier at SWR higher than 3.0 and power higher than 600W.
    That means that with lower power the amplifier can operate also with higher SWR.
    There is another protection for high temperature and one for the driving power.
    We also have an hardware protection before the filters; in case of mismatching due to filter problems the amplifier is inhibit.
    The microprocessor also controls the fans with 3 different controls; fans are off till the reach of 38 degrees Celsius, fans at half speed up to 50 degrees and fans at full speed over that level.
    To get a good heat dissipation we used a heatsink with elements 80 mm high and 4  120mm fans by PAPST.
    The fans are 36-58V but they are powered with 27 volts so they are very silent with a very good air flow. 



    More info , photo , data , will be publish in next days, this only preliminar page with old photo.

      
    SOURCE OF PARTS , REFERENCES , LINKS

  • AN749 AN749 Broadband Transformers an power combining
  • EB104 EB104 Get 600 Watt from four mrf150 Motorola Engineering Bulletin
  • An excellent exaustive site written by k0gkd can be found here
  • An excellent overview article written by Helge can be found here
  • N4IP's excellent write-up of his MRF157 amp project is here
  • WM5Z is also working on an amp, and his very nice site is here
  • Project Gamma site is here
  • The Yaesu VL-1000 Quadra HF Linear
  • KK4MC's Solid State Ampflier Pages
  • OH8JEP's project page



  • Numero accessi a questa pagina dal 5/12/08- Totale [Count not available in text mode]



     

    Inviate i vostri commenti e le vostre richieste a:Alfredo Rosati I5UXJ-KJ6R  Contatto con il sysop[email protected]

    Page updated 02-11-2008
    solid state hf linear amplifier amplificatori lineari hf home made con 4cx800 gu74b mrf 150 eb104 3cx1200a7 gs35b 4cx250 gu84b
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