|
It will put out a conservatively-rated 15 watts across the FM broadcast
band.
PCB :
Components placement :
The flange on the MRF136 may be directly mounted to a heatsink with two
4-40 machine screws, if the heatsink is drilled and tapped. A specially-shaped hole must be cut in the PCB to accept
the flange and body of the MRF136 as shown by the thin outline on the photomask.
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 |
27 Ohms / 1W , Thin Film |
01
|
|
C8 |
100uf / 40 V |
01
|
| R2 |
10 KOhms / 0.25 W |
01
|
|
C9 |
0.1 uf |
01
|
| R3 |
10 KOhms / Multi Turn |
01
|
|
C10 , C11 |
680 pf / Feedthru |
02
|
| R4 |
1.8 KOhms / 0.5 W |
01
|
|
L1 |
2 Turns , 0.29" ID , # 18 AWG , 0.10" Long |
01
|
| C1 , C2 |
15 - 115 pf |
02
|
|
L2 |
2 Turns , 0.23" ID , # 18 AWG , 0.10" Long |
01
|
| C3 |
8 - 60 pf |
01
|
|
L3 |
2.25 Turns , 0.29" ID , # 18 AWG , 1.25" Long |
01
|
| C4 |
43 pf |
01
|
|
RFC1 |
20 Turns , 0.30" ID , # 20 AWG ( Closewound ) |
01
|
| C5 |
24 pf |
01
|
|
RFC2 |
Feroxcube , VK-200 , 19/4 B |
01
|
| C6 |
680 pf |
01
|
|
D1 |
1N5925A |
01
|
| C7 |
0.01 uf |
01
|
|
Q1 |
MRF136 |
01
|
Reference :
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|
Last
Updated : September 17, 2001