RF amplifier PA70E on RD70HVF1

RF amplifier PA70E on RD70HVF1
by Peter SP2DMB
www.sp2dmb.blogspot.com
ver. 1.0 13.08.2014
www.sp2dmb.cba.pl
sp2dmb@gmail.com
Shows a further my design. This time, a more simplified version of the power
amplifier - PA70E (Economic). The minimum elements of maximum effect.
Depending on input signal, the output power on 70MHz will inrange 40-50W.
The amplifier can work CW, SSB and FM.
The design is based on mosfet transistor manufacturing by MITSUBISHI RD70HVF1. Practice has shown that it is very resistant to destruction. NOTICE !
Don’t exceeds gate-source and temperature limit.
The plate is one-sided, tinned with solder mask. Plate size: 52x131mm.
Diagram is typical for this type of design. This project is modeled on the datasheet.
The amplifier consists of several blocks:
- RF VOX - if the problem is to control the amplifier, this circuit should be applied.
When RF signal appears, two relays are energized: input and antenna relays. Delay
from transmit to receive is regulate PR 4,7k
- FAN - may be needed if the heat sink is too small. To reduce the fan current shall
be connected resistor in series (or a few). Selected so that the performance of the fan
enough to cool the heat sink. You can not use resistors, but will increase the noise
produced by the fan.
- PA - amplifier with RD70HVF1.
- Bridge PWR – this circuit can be used to display output power. Display can be tilt
meter or LED indicator. Maximum voltage from this circuit is regulate PR 4,7k. If the
output voltage will be too small is needed additional D5.
- LPF - simple LPF filter 70MHz
MOSFETs have characteristics similar to the lamp. This feature allows to
control in wide range (mW to watts).
Tests done with transverter TS70 has produced more than 30W output power !!!
And now the technical details.
I used to build the heatsink with dimensions 165.5 x 100 x 35mm
The first step is to make a rectangular hole to transistor. Cut out a green field
with the mark “RD70HVF1”, to edges of the metallization.
NOTE! Do not cut out the extreme edge of the plate !!! The bridge should be
soldered to the ground and connected to the screw of transistor (source
RD70HVF1). The drain current of the transistor is flowing by two bridges !
The next step is drilling and grooving holes for mounting plate, transistor and
fan. The plate should be placed on the heatsink so that the power transistor was at
the middle of the heatsink.
Soldering always begin from the filters. This is comfortable to measure
process.
In the next step we are starting from relay antenna.
Below pictures of the assembled amplifier:
Before mount the transistor, set the slider PR 4,7k to ground. Connect 13.8V
voltage to pin + PTT. Check the voltmeter adjustment range gate bias voltage of the
transistor. The range is from 0 to approx. 2.7V (3V). Set the slider to the groun again.
NOTE ! The image shows the transistor, but this one should be not mounted !!!
If everything is fine, coat the bottom of transistor thermal grease and put this
one to a hole in the plate. Screws transistor and bridges.
Connect the voltage 13.8V to “+ PTT” and point marked “+” - the orange wire
in the picture –
Set PR 4,7k voltage on the gate in the range of 1.9 to 2.1V. We control and set
the drain current at range 40-50 mA.
Now time to test. To testing I used transverter TS70 and PA70E. To control
the voltage, current and power consumed by the system I usem my construction MULTIMETER.
Description of MULTIMETER can be found here:
http://www.sp2dmb.cba.pl/projeng.html
PA connect through 5A fuse.
The first regulation: set TRX on SSB mode. Press PTT and see if anything
disturbing happens. My set (TS70 + PA70E) have quiescent current about 0.34A
(including 3 relays). We speak into the microphone. On the power meter should be
immediately output power. Set TRX in RTTY mode (full carrier). Press the PTT and
adjust the trimmers of amplifier to achieve maximum output power.
My power meter showed 30W output power !
This amplifier works with my other transverters: TS70 and TH70 or other
transverters.
On the board there are two 2 pins marked “RX”. This pins should be
connected to input circuit of transverter.
When we are operating digital modes, may be needed to cool the heatsink fan.
Long screws fixing the fan can be used to attach the entire PA.
The fan has dimensions of 92 x 92mm. Speed control is performed using
resistors with a capacity of at least 2W. We select the value of the resistors to
enough cold the heatsink during testing of WSJT or FM. You can also build a
regulated power supply to the fan on the LM317.
On the board is a simple stripline detector for power output display .
The level of the output voltage adjust PR 4,7k (5k). This voltage can be shown
on milivoltmeter, LED (eg. 10mm diameter) or LED line. The output marked "RF".
I hope that this description will encourage colleagues to build an amplifier.
MITSUBISHI mosfet transistors are for me the best solution in this type construction.
Link to the video on YouTube:
https://www.youtube.com/watch?v=wb8vxSSwI8Q
If you have any questions - email me: sp2dmb@gmail.com
I wish you success in building and much DX-s !!!!
73 – Peter SP2DMB
Assembly diagram
Elements:
C3
= 1 x 100p/100V
C12
= 1 x 10µ
C20
= 1 x 22p/100V
C21
= 1 x 25p
C22
= 1 x 65p
C26
= 1 x 2,2p
C1,C23
= 2 x 47p/100V
C17,C19
= 2 x 40p
C2,C4
= 2 x 68p/100V
C24,C25
= 2 x 56p/500V MICA
C5,C8,C10,C14,
C29,C30,C31 = 7 x 4,7n
C6,C7,C11,C15,
C16,C18,C32,
C33,C34
= 9 x 100n
C9,C13,C27 = 3 x 100µ
L2
L4
L5
L6
L11
L3,L7
L8,L9,L10
= 1 x 10t/6,5mm/1,3mm
= 1 x FB
= 1 x 5t/6,5mm/diam 1mm
CuE
= 1 x 15uH
= 1 x 15µH
= 2 x VK200
=3x
P,P,P
= 3 x 4,7k PR
Q1
Q2
= 1 x RD70HVF1
= 1 x BDP953 option
D1
= 1 x 2,7V
D5
= 1 x 1N4148 opt.
D2,D3,D4,D6,D7 = 5 x 1N4148
R1
R2
R3
R4
R5
R6,R7
= 1 x 120
= 1 x 820
= 1 x 8,2k
= 1 x 2,2k
= 1 x 150
= 2 x 270/2W opt.
L1
= 1 x 2t/6,5mm/CuAg 1mm
Rel1,Rel2
= 2 x 2 x Um
FAN
= 1 x option