This dokumentation concerns the construction of a power amplifier for the 4m band. The main part of the device is mosfet Mitsubishi RD70HVF1 . Although it is dedicated to the higher band, but it is stable at 70MHz. The ranges of output power from 45 to 55W, with input powerl about 3-5W. The system is powered by a standard voltage 13,8 V and consumes approx 7- 8A. The amplifier consist of: power transistor and additional elements, that allow for quick configuration of any device . Therefore, the board includes all the necessary blocks for a complete amplifier. PCB is one-sided, plated with solder mask . Dimensions: 84x146mm . The amplifier have a simple security circuits : ovecurrent, exceeded SWR and temperature control. These additional circuits will allow for the safe use of the amp and let a smaller heat sink assembly . The size at which the heat sink is not required for the fan is: 124x150x35mm Kits will be available in two versions: PA70HLI and PA70H . The first version will require input signal abt. 100mW ( LI - Low Input ) and requires an additional driver amplifier - PA70. Second version approx max. 3 -5W (H - high) . The amplifier can to be control to transmition mode – PTT:
- By giving GND (standard) : -P - By giving +13.8 V: +P - RF VOX - automatically turns on when a signal rf (with adjustable delay)
Amplifier box hes dimensions of 160 x 80 x 190mm . The heatsink hes additional
place for driver PA70 . On the following pages is a description of the amplifier PA70H .
Below is a block diagram:
1.RF VOX - allows you to work without additional cable for PTT . To use it you must set a time constant DELAY by potentiometer . The PCB includes two space for electrolytic capacitors (if need). 2. PTT PLUS - amplifier can be started by entering the +13.8 V input . 3. PTT GND – entering mass – GND, amplifier is switching for transmitting . 4. FAN TEMP CONTROL - this is a temperature sensor based on the LM35 . This sensor is located close to the power transistor and is connected through the thermal grease to the heat sink. When temperature increase signal from the sensor increase also. This signal come in to amplifier LM358, After amplification drives the transistor BD139 and the fan start. Potentiometer P1 you can adjust the threshold of the fun. Fan speed is directly proportional to the temperature. 5. ATMEGA8 PA CONTROL - optional add-on to the amplifier. This is the RF Multimeter that the display shows : supply voltage U , current I, DC power P, graphic display of the RF output power , heat sink temperature t and SWR. 6. INP / OUT – relay, switching rf input signal. 7. PA RD70HVF1 - 50W amplifier. 8. SWR BRIDGE - measuring bridge:FWD and REF . RF – bridge signals may control: MULTIMETER , microampere , LED line . If the signal is too small , it can be amplified in the second - free operational amplifier . The outputs of the bridge can be adjusted using potentiometers . 9. L PF- 70MHz low pass filter. 10. FINGER – antenna relay.
11. SWR ERROR - protection against excessive SWR . Exceeding the predetermined level execute reduction of the gate voltage to zero. Power drops from 50W to 30W, and the current of 7A to 4A. The block is equipped with a second exit for any driver , for example - PA70 with RD16HHF1. 12. BIAS PROTECT - executive transistor, which reduce voltage to zero when then SWR is over 2. It has an additional output . 13. DRIVER POWER CONTROLLER - this is a regulated power supply. Allows for smooth power control driver with driver RD16HHF1. By varying the drain voltage (5 to 11V ) - the output power is change continuously.
Circuit diagram:
The blocks:
Assembly circuit:
Installation and commissioning I used heat sink: width 124mm,height 35mm. It may be smaller, but you will need to apply the fan (the control is on the board). The length of the heat sink is 146mm, as much as the PCB. Fasten the plate to the heatsink and drill the holes. Then rifling on the M3. If there is a PA with + driver, do the holes for the PA70. PCB PA70H must be extremely placed, so that RD70HVF1 fell in the middle of the heatsink (better heat removal).
After this we remove the chips remaining after treatment:
After screwing the pcb, we must do soldering diodes 1N4148:
Capacitors, inductors and other elements:
Before installing the power transistor RD70HVF1, check the operation all circuits: RF VOX, PTT by GND (-P), PTT by +13,8V (+P), threshold of the fan if need.
Potentiometer 4.7k for BIAS of transistor (RD70) set to GND.
Connection diagram
Some pictures for explain:
Relay INP/OUT. Coaxial cable left - INP/OUT 70MHz. Right bypass for RX.
From left side: black POT 50k - setting DELAY when switching from transmit to receive, at the top (visible part) - 4,7 k - adjustable output voltage LM317 power
supply, at the bottom of the 4.7 k - setting the gate voltage RD70HVF1. On the right fallows: polymer fuse 6A (yellow), at the bottom of the fuse there is
place for LM35 temperature sensor.
Top left: potentiometer (black) - gain control of the second operational amplifier, on the right ( also black) – adjusting threshold fan (system works with LM35 thermometer). Two blue potentiometers: top - REF reflected voltage regulation, bottom - FWD forward voltage regulation. Signals comes from SWR bridge – a photo below:
In the same shield box is the relay antenna (FINDER) and LPF:
Power amplifier stage with RD70HVF1. Use additional connectors (wire CuAg) to solid connect source to the GND. Please remember to coat thermal grease the bottom of transistor !!!
Power amplifier in box:
Connect voltage to the PA and switching it to transmitting (without RF input signal). Potentiometer 4.7k set the voltage approximately 1.9 -2.0 V at the gate of the transistor:
Connect input rf signal and adjust to the highest power output (VR capacitors).
And now I present the achievements of the amplifier PA70H. Amplifier working in two configurations. First - control driving from directly from the transverter TS70, second - with an additional driver on RD16HHF1 - PA70 (by SP2DMB). 1. Control from the transverter TS70. Transverter output power is about 100mW, with PA70H power increases 30W !
+ = 30W
Transverter TS70 Amplifier PA70H 2. Control from additional driver - PA70 Transverter TS70 + amplifier PA70 output power is approximately 3,5 W (output power can be more by adjusting LM317). Output power increased to about 45W. While various attempts got power more than 50W out !. Depending on the matching, power will vary between 45-55W.
Video on YouTube: http://www.youtube.com/watch?v=6-cXMDKAvjg&feature=youtu.be
I hope that this description will allow for the construction of amplifiers not only for the band, and MOSFETs Mitsubishi are really recommendable transistors !
= 1 x Finder Ant1 = 1 x Antenne C2 = 1 x 68p/100V C3 = 1 x 100p/100V C4 = 1 x 68p100V C20 = 1 x 40p C32 = 1 x 12p C34 = 1 x 22p C36 = 1 x 2,2p C37 = 1 x 47µ C38 = 1 x 22µ C45 = 1 x 25p C50 = 1 x 1µ C57 = 1 x 47µ* C1,C63 = 2 x 47p/500V C12,C49 = 2 x 10µ C21,C22 = 2 x 56p C33,C46 = 2 x 65p C5,C8,C10,C14, C17,C18,C23, C41,C42,C43, C58,C62 = 12 x 4,7n C6,C7,C11,C15, C19,C24,C25, C26,C27,C28, C29,C30,C31, C35,C39,C40, C44,C48,C51, C53,C54,C55, C56,C59,C60, C61 = 26 x 100n C9,C13,C52 = 3 x 100µ D3 = 1 x 2,7V D1,D2,D4,D5,D6, D7,D8,D9,D10, D11,D12 = 11 x 1N4148 F1 = 1 x 12A F polimer1 = 1 x 6A Jp1,Jp2 = 2 x Jumper L1 = 1 x 2t/6,5mm/CuAg 1mm L2 = 1 x 10t/6,5mm/1,2mm L4 = 1 x FB L5 = 1 x 5t/6,5mm/diam 1mm CuE L6 = 1 x 15uH L11,L12,L13, L14 = 4 x 33µH L3,L10 = 2 x VK200 L7,L8,L9 = 3 x LED1,LED2 = 2 x
M = 1 x Motor P,P,P,P,P3 = 5 x 4,7k PR P1,P2 = 2 x 22k PR Q1 = 1 x RD70HVF1 Q2 = 1 x BD139 Q3 = 1 x BDP953 Q6 = 1 x BC 547 Q4,Q5 = 2 x BCP52 R1 = 1 x 120 R5 = 1 x 820 R15 = 1 x 8,2k R23 = 1 x 240 R16,R19,R21 = 3 x 2,2k R2,R9,R14,R18, R20,R22 = 6 x 1k R3,R4 = 2 x 220 R6,R10,R12,R17, R24 = 5 x 4,7k R7,R13 = 2 x 100k R8,R11 = 2 x 1,8k Rel1 = 1 x 2 x Um SW1 = 1 x 1×ON U1 = 1 x LM358 VR1 = 1 x LM35DZ VR2 = 1 x LM317
