|
It will put out a conservatively-rated 300 watts across the FM broadcast
band.
PCB :
Components placement :
All holes indicated by black dots MUST be connected to the solid foil
side on the back of each board. These are the ground connections. A simple feed through, or a short piece of buss
wire will do.
The flange on the MRF141G must be mounted to a heat spreader, a copper
plate 5/16" thick and 6" x 8", which is then mounted to the heatsink with 6-32 machine screws, if
the heatsink is drilled and tapped.
I recommend buying the two transformer assemblies, rather than trying to build them, because 15-ohm hardline is
not easy to find. I have had good results ordering them from:
RF power systems
17827 North 26th St.
Phoenix, AZ 85032
1-602-867-0389
The part numbers are TUI-9F and TUO-9F and the cost is about $20 each.
This amplifier has the notable characteristic of variable gain control via the bias adjustment trim pot. It may
be used in conjunction with an SWR bridge circuit to limit power output in the event of high SWR caused by damage
to the antenna during a storm, or someone inadvertently disconnecting the coax transmission line. If you wish to
implement a failsafe shutdown system that is triggered by loss of PLL lock, I still recommend a power supply cutoff
relay for total safety however.
Component List :
|
Component
|
Value
|
Qty
|
|
Component
|
Value
|
Qty
|
| R1 |
1k, 0.5 W |
01
|
|
C3 |
0.1 uF Ceramic Chip |
01
|
| R2 |
10k, 0.5 W |
01
|
|
C4 , C5 , C12 |
1000 pF Ceramic Chip |
03
|
| R3 |
330 Ohms , 2 W |
01
|
|
C6 , C7 |
0.01 uF Ceramic Chip |
02
|
| R4 |
1k ( Pot. ) |
01
|
|
C8 |
0.47 uF Ceramic Chip |
01
|
| R5 |
68 KOhm , 0.25 W |
01
|
|
C13 |
300 pF, 2x150 pF Ceramic Chips |
01
|
| R6 |
Thermistor 10K at 25 degC Sk at 75degC |
01
|
|
L1 |
10 Turns AWG #16 Enameled Wire |
01
|
| R7 |
2k, 0.5 W |
01
|
|
L2 |
Ferrite Beads over AWG #16 Wire |
01
|
| R8 , R9 |
25 Ohm Microwave Power Resistor |
02
|
|
L3 , L4 |
Lead Lengths of R8 and R9 |
02
|
| C1 , C9 |
1.5-20 pF Compression Mica |
02
|
|
FET |
MRF141G |
01
|
| C2 |
200 pF Ceramic Chip |
01
|
|
|
|
|
| |
|
Component
|
Value
|
Qty
|
| T1 |
9:1 RF Transformer |
01
|
| T2 |
1:9 RF Transformer |
01
|
|
|
| |
|
| |
|
| |
|
Reference :
Download the page | RF / Video | Circuits | Electronics | Home
|
Last
Updated : September 17, 2001