RF amplifier 70MHz on RA30H0608M

Transcription

1 RF amplifier 70MHz on RA30H0608M Peter SP2DMB r. The availability of a hybrid power amplifier allows easy to built RF power amplifier for any transverter. Module MITSUBISHI RA30H0608M need to be drive only 50mW of power than increase it to 30 watts. You can get more power - 45W, but it can be quickly damage. It is recommended to set a maximum 30 watts. Plate to the amplifier is one-sided, tinned with solder mask. Board dimensions: 131 x 36mm. The application is typical, but includes some additional simple blocks: - ATT PI attenuator. Adjusts the control RF power from transverter. Maximum RF power to module is 50mW - BIAS - a simple voltage regulator on LM1117-5V. Potentiometer P1 adjust the quiescent current of the module - Idd - RA30H0608M - power module - LPF - Low Pass Filter - SWR bridge - a simple bridge for the measurement of the FWD and SWR On the next page is a scircuit diagram of the amplifier.

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3 Description of the assembly and blocks In the construction of amplifiers SMD technology, always begin from the mechanical work. Mounting plate is fixed to the heatsink. The module there was placed in the middle of the heat sink. Execute immediately holes for mounting the fan and in heatsink of PA. After completing these steps, the first step is soldering only LPF. On the board provides for the use different types of low pass filters. In the film shows a simple dual-filter with three capacitors 55pF (22pF + 33pF/100V). The coils L3 and L4 have 7 turns, and made from wire CuAg with a diameter of 1mm (easy to solder). Winding diameter 8mm. The distance between the coils approx mm.

4 Simulation of the filter by the program RFSimm99: As you can see the second harmonic suppression is approx. 39dB. Below is a chart made by NWT500: The actual attenuation is about 46dB. The important third harmonic 210MHz is suppress at the level of approx. 43dB.

5 The second version of the almost ideal filter can we made according to the description Bo OZ2M ( ). Scheme is as follows: Characteristic of this filter is very good. Eliminates 2 harmonic at 65dB and 3 harmonic approx. 90db!!! Below the simulation RFSimm99: The filter plate is here:

6 The next step is the installation of supply to BIAS. It is built on the stabilizer LM1117-5V. Connect +13,8V to point + PTT. Check the potentiometer P1, range adjusting should be from 0 to 5V. After checking set voltage level on the slider P1 = 0V. Installation diagram: We assembly the rest of the elements (without power module). At the end we mount a power module - RA30H0608M. This module works with big quiescent current Idd - approx. 0,55A (or more). Must have good cooling. For this purpose, grease by thermal paste the bottom of the module:

7 Apply on the middle legs of the module ferrite beads FB. That avert the possibility of appearance RF voltage on BIAS and drains of transistors. Attach to the heatsink and press until the paste comes off outline of module: Screw the module to the heatsink and solder 4 connectors of the module:

8 We need to make additional mesh-connector GND module. This is very important because total current flows via drain is approx. 6A! Attenuator ATT. If you do not have the ability to set output power of the transverter this one is necessary. Maximum input power of the module is 50mW. The following table shows values of resistors to the ATT: Let us remember the power rating resistors is depending to the power of the transverter. In order to increase the power, you can solder SMD resistors on the so-called "sandwich" or let's use metalized resistors - THT (metal-oxide). Now time to test! We assemble the set of test: TRX, transverter and our PA. For measurement voltage, current and power drain, I used my MULTIMETER ( ):

9 To the output of amplifier connect: reflectometer, measurement of power output and ATT. Connect the pin "+ PTT" and "+". Connect the voltage 13.8V to the kit. Drain current Idd of module is not yet set. By potentiometer P1 set the current drain at about 0.4A. By changing the voltage BIAS (increasing) we cause so the module begins to amplify linearly. In my case quiescent drain current Idd increase to approx. 0,55A, and the voltage bias -> approx. 4.5V.

10 During the tests, total current of the set is approx. 0.84A. That's quite a lot. The manufacturer specifies a module efficiency of 40%. The amplifier has not any control points, only BIAS. After changing emission on RTTY (full carrier) got more than 30W output power at 78W DC power input. The efficiency of approx.of 42%: The module easily give much more power, but in the case of any mismatch we can damage it. It is recommended to use it with an output power - 30 watts. Especially, because quiescent current is very large, and working WSJT digital modes, gives off a great deal of heat. The fan for cooling in this case is necessary!!!

11 After the filter LPF there is a simple SWR bridge. The voltage induced in the stripline can be used to connect the indicator or LED. SWR signal can be used to secure the module, eg. against damage.

12 Control of amplifier. Giving V to point "+ PTT run power BIAS and energize antenna relay. Drain voltage is connected permanently. Let's use the polymer fuse (multi) or fuse. Rated current 5-6A. Summary. The module allows simple and rapid increase a power output. Works without any excitation and stable. The disadvantage is the large quiescent current - more than 0.5A / 7.5W inp., where a similar amplifier with transistor RD70HVF1 takes only 50-60mA!!! Examples are my other amps: PA70H and PA70E. See: The absence of any regulatory elements (except BIAS), the amplifier operates "on the spot". I wish you success in building and DX-s to 4m!!! If you have any questions, doubts, write to me: sp2dmb@gmail.com Descriptions of other amps at 70MHz, you will find on my website: or The presentation of this amplifier can be viewed on YouTube at: 73 Peter SP2DMB Component list C13 = 1 x 1000µ THT C1,C3,C5,C7, C14,C15,C22, C23 = 8 x 4,7n C16,C17,C19 = 3 x 56p/100V C2,C6 = 2 x 22µ tant. C20,C21 = 2 x 1n C4,C8,C11,C12, C18,C24 = 6 x 100n C9,C10 = 2 x 10µ D3 = 1 x 1N4148 opt. D1,D2,D4 = 3 x 1N4148 L1,L2 = 2 x VK200 L3,L4 = 2 x patrz schemat P1 = 1 x 100 P2,P3 = 2 x 4,7k R1,R2,R3 = 3 x patrz tabelka R4,R5 = 2 x 220 Rel1 = 1 x FINDER RF = 1 x RA30H0608M VR1 = 1 x LM V Goldpin = 9 x