PRO and CON
By Dave Russell, W2DMR
Forest Cummings, W5LQU
1
RF Drive
PA
AC?
ALC
Cooling
AC Power
PS
2
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
3
4
5
6
7
8
9
10
11
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
12
 TETRODES
TRIODES
811 A
572 B
3-500 Z
3 CX 800 A7
3-1000 Z
3 CX 1200 A7
3 CX 1500 A7
25.00
50.00
189.00
850.00
850.00
?
950.00
4
4
4
4
4
4
4
X 150
CX 250 B
CX 350 B
CX 400B
CX 1000 A
CX 1500 B
CX 1600 B
?
185.00
190.04
350.00
600.00
1275.00
?
13
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
14
Watts
S units
dB
1500w
800 w
400w
100w
25w
5w
1w
S9
S 8.5
S8
S7
S6
S5
S4
+12
+9
+6
0dB ref
-6
-13
-20
15
DIPOLE ANTENNA
100 WATT TRANSCEIVER
11
300W
CPLR
0dB Reference
16
240 VAC
100 WATT TRANSCEIVER
11
1500 W
POWER
AMP
DIPOLE ANTENNA
1500W
CPLR
+12dB
(2 S units)
17
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
18
Cushcraft 3 element tribander (20-15-10m) 8dBi/25dB fb
Hygain 3 element tribander (20-15-10m) 8dBi/25 dB fb
$549
$419
40 foot tower $669
50 foot tower $939
Rotator HAM – IV $589
Total cost = $1677 to $2077
19
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
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
20
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
21
•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
22
SPEND YOUR MONEY ON
YOUR ANTENNA FIRST,
THEN GO ON TO A
POWER AMPLIFIER !
23