POWER AMPLIFIERS

PRO and CON

By Dave Russell, W2DMR

Forest Cummings, W5LQU

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PA

PS

AC?RF Drive

ALC

AC Power

Cooling

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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

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Rated Power Output – EfficiencyClass C – Class AB1Max allowable VSWRModes – SSB – CW – Digital – RTTYPlate Voltage – Collector VoltageStatic CurrentMax Full Load Plate/Collector currentTuning Required – Network/Antenna CouplerDrive required Cooling required – BlowerALC providedInput AC power – 120v/240v

TRIODES 811 A 25.00 572 B 50.00 3-500 Z 189.00 3 CX 800 A7 850.00 3-1000 Z 850.00 3 CX 1200 A7 ? 3 CX 1500 A7 950.00

TETRODES 4 X 150 ? 4 CX 250 B 185.00 4 CX 350 B 190.04 4 CX 400B 350.00 4 CX 1000 A 600.00 4 CX 1500 B 1275.00 4 CX 1600 B ?

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Power Out – Splatter - Distortion

RF drive – splatter – grid damage - distortionALC – too much – pumping - distortionNeutralizing – instability – parasitesLow line voltageCooling – RTTY – voice/CWFilament Voltage – tube life – low emission - low outputIncorrect Loading – distortionIncorrect Static current (bias) - distortion

Watts S units dB

1500w S 9 +12800 w S 8.5 +9400w S 8 +6100w S 7 0dB ref25w S 6 -65w S5

-131w S4

-20

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11100 WATT TRANSCEIVER 300WCPLR

DIPOLE ANTENNA

0dB Reference

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11100 WATT TRANSCEIVER 1500W CPLR

DIPOLE ANTENNA

+12dB (2 S units)

1500 WPOWER AMP

240 VAC

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AL-811H4-811A Tubes800 w output120 vac$799Tube cost $90

AL-80B3-500Z Tube1000w output120/240 vac$1329Tube cost $189

AL-15003CX1500A7 (8827)1500w output240 vac$3349Tube cost $1275

Antenna CouplerMFJ 989D1500w50 ohm Dummy LoadSWR Meter4:1 Balun6 position switch$390

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Cushcraft 3 element tribander (20-15-10m) 8dBi/25dB fb $549

Hygain 3 element tribander (20-15-10m) 8dBi/25 dB fb $419

40 foot tower $669

50 foot tower $939

Rotator HAM – IV $589

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Total cost = $1677 to $2077

100w3 element beam40 foot towerHAM-IV Rotator6dB increase in ERP6dB increase in received signal10/20 dB less QRMCost = $1707

800 wattsAL-811 PAMFJ 989D Ant Cplr40 foot tower3 element beamHAM-IV Rotator15 dB increase in ERP6dB in receive10/20 dB less QRMCost = $2896

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AL-1500 Power AmplifierMFJ989D Antenna Coupler3 Element Triband Beam40 foot towerHAM-IV Rotator240 vac service18dB increase in ERP6dB increase in Receive10/20 dB less QRMCost = $5646

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•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 requiredAntennas help both TX and RX signals

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SPEND YOUR MONEY ON YOUR ANTENNA FIRST,

THEN GO ON TO A POWER AMPLIFIER !