1. PRO and CON By Dave Russell, W2DMR Forest Cummings, W5LQU
POWER AMPLIFIERS
PRO and CON
By Dave Russell, W2DMR
Forest Cummings, W5LQU

2. Basic power amplifier
RF Drive PA
AC?
ALC
Cooling
AC Power PS

3. POWER AMPLIFIER TYPES Vacuum Tube
High impedance – high voltage – danger!
Tuned network – PI – 3:1 VSWR – No Coupler
Two versions – Grid Driven /low drive
Grounded Grid/high drive
Solid State
Low impedance – high current
Fixed tuning – 50 ohms – max VSWR 2:1
Two versions – Bipolar Junction Transistors
Field Effect Transistors

4. VACUUM TUBE PA (hv/lc)

5. Vacuum Tube gg,pi-l

6. Tetrode power amplifier

7. SOLID STATE PA (hc/lv)

8. SOLID STATE PA DETAILS

9. AMERITRON AL-80B (3-500)

10. AMERITRON AL-1500 (3CX1500)

11. AMERITRON ALS-1300 (FET)

12. Power amplifier ratings
Rated Power Output – Efficiency
Class C – Class AB1
Max allowable VSWR
Modes – SSB – CW – Digital – RTTY
Plate Voltage – Collector Voltage
Static Current
Max Full Load Plate/Collector current
Tuning Required – Network/Antenna Coupler
Drive required
Cooling required – Blower
ALC provided
Input AC power – 120v/240v

13. LINEAR POWER AMPLIFIER TUBES
TRIODES
811 A
572 B
3-500 Z
3 CX 800 A Z
3 CX 1200 A7 ?
3 CX 1500 A
TETRODES
4 X ?
4 CX 250 B
4 CX 350 B
4 CX 400B
4 CX 1000 A
4 CX 1500 B
4 CX 1600 B ?

14. Possible problems (troubles)
Power Out – Splatter - Distortion
RF drive – splatter – grid damage - distortion
ALC – too much – pumping - distortion
Neutralizing – instability – parasites
Low line voltage
Cooling – RTTY – voice/CW
Filament Voltage – tube life – low emission - low output
Incorrect Loading – distortion
Incorrect Static current (bias) - distortion

15. POWER, S units, & Dbs Watts S units dB w S 9 +12 800 w S 8.5 +9
100w S 7 0dB ref
25w S 6 -6
5w S5 -13
1w S4 -20

16. THE BASIC 100W STATION DIPOLE ANTENNA 11 100 WATT TRANSCEIVER 300W
CPLR
0dB Reference

17. THE BASIC 1500W STATION DIPOLE ANTENNA 240 VAC 11 1500 W POWER AMP
100 WATT TRANSCEIVER
1500W
CPLR
+12dB
(2 S units)

18. power amplifiers AL-811H 4-811A Tubes 800 w output 120 vac $799
Tube cost $90
AL-80B
3-500Z Tube
1000w output
120/240 vac
$1329
Tube cost $189
AL-1500
3CX1500A7 (8827)
1500w output
240 vac
$3349
Tube cost $1275
Antenna Coupler
MFJ 989D
1500w
50 ohm Dummy Load
SWR Meter
4:1 Balun
6 position switch
$390

19. antennas Cushcraft 3 element tribander (20-15-10m) 8dBi/25dB fb $549
Hygain 3 element tribander ( m) 8dBi/25 dB fb $419
40 foot tower $669
50 foot tower $939
Rotator HAM – IV $589
Total cost = $1677 to $2077

20. Possible configurations
800 watts
AL-811 PA
MFJ 989D Ant Cplr
40 foot tower
3 element beam
HAM-IV Rotator
15 dB increase in ERP
6dB in receive
10/20 dB less QRM
Cost = $2896
100w
3 element beam
40 foot tower
HAM-IV Rotator
6dB increase in ERP
6dB increase in
received signal
10/20 dB less QRM
Cost = $1707

21. Maximum configuration
AL-1500 Power Amplifier
MFJ989D Antenna Coupler
3 Element Triband Beam
40 foot tower
HAM-IV Rotator
240 vac service
18dB increase in ERP
6dB increase in Receive
10/20 dB less QRM
Cost = $5646

22. pa pros & cons Power Amplifiers can give maximum ERP
PA s really help on DX pileups and contests
PA s don’t help the received signal or QRM
Power Amplifiers are very expensive
Power Amplifiers are dangerous (high voltage)
Over about 800 watts you need 240 vac line
HI Power Antenna Couplers and Dummy Loads
are required
Antennas help both TX and RX signals

23. SUMMARY (the bottom line)
SPEND YOUR MONEY ON YOUR ANTENNA FIRST,
THEN GO ON TO A POWER AMPLIFIER !