|This page describes how I assembled a 23 cm PA kit based on the Mitsubishi RA18H1213G power module. All components except the power module were purchased from Bert Modderman PE1RKI. He is a wizard with his CNC milling machine. Mechanical parts sold by him are beautiful and perfect!|
|Component||Circuit Diagram||Delivered with kit|
|C2, C5, C8, C9||47 nF||6n5 SMD|
|C4, C6, C7, C10||10 µF||22 µF SMD|
|R1, R2, R3, R4||220 ohm||240 ohm SMD|
Click any image to enlarge. Hit "Back" to return here.
Figure 3. Kit from PE1RKI.
Figure 4. Bottom side of PCB.
The delivered PCB did not have plated-through holes (plated-through holes connect top side tracks with bottom side tracks). I soldered 5 wire bridges and made the bottom side smooth using a file. As you can see, some of the wire bridges are inferior (my fault - too much filing). Lastly, the PCB bottom side was thoroughly cleaned.
Figure 5. Print lay-out.
Figure. 6. The PCB is fastened with 5 screws.
There was an error on the PCB. I had to cut a copper track. It is marked in the picture above. Click the picture for a better view.
I checked the connection between the metal house and the 3 ground connected tracks. The diode tester showed 0.00 volt, which indicates a perfect connection with no voltage drop.
The PCB stays in the house during soldering of the remaining components.
Figure 7. Sanding the bottom side of the power module.
To make the bottom side of the power module smooth, I first removed the two metal protrusions with a file. Then followed sanding to further smooth out the surface.
Figure 8. Bottom side of the power module.
The picture shows the bottom side of the power module, which is ready for fitting into the metal house. Input and output wires were soldered to ground to prevent ESD during sanding.
Figure 9. All components soldered.
The RA18H1213G module is mounted without any thermal compound. A solid RF ground is more important than slightly improved heat transfer.
I have added a short piece of wire between the cathode of D1 and the leftmost ground track. This wire is optional.
The input connector (sma female) is seen to the left; the output connector is to the right.
The grey feed-through capacitor carries Vdd and the red one enables bias (apply +12 V). The bias voltage Vgg is set with the black trimpot.
Fig. 10. The black heat sink measures 200 mm x 75 mm.
The metal house is fastened to the heat sink by 4 screws in the corner. A thin layer of "Arctic Silver 5" is applied between the metal house and the heat sink in order to enhance heat transfer.
Figure 11. The heat sink is 40 mm high.
Figure 13. The finished PA (top side).
I did not use the two small fans included with the kit. The 80 mm fan in the picture is powerfull and almost noiseless. The air is blown from above onto the heat sink and distributed between the fins.
|Pin||Pout||Bias Current||Total Current|
|300 mW||23 W||3.5 A||8.2 A|
|400 mW||23 W||3.5 A||8.4 A|
|100 mW||15 W||1.0 A||5.2 A|
|200 mW||20 W||1.0 A||6.4 A|
|300 mW||21 W||1.0 A||6.7 A|
|100 mW||5 W||0.4 A||2.9 A|
|200 mW||17 W||0.4 A||5.2 A|
|300 mW||19 W||0.4 A||5.9 A|
Written by OZ1BXM Lars Petersen. Latest revision 06-Feb-2017.