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POWER AMPLIFIERS

POWER AMPLIFIERS. PRO and CON By Dave Russell, W2DMR Forest Cummings, W5LQU. Basic power amplifier. RF Drive. PA. AC?. ALC. Cooling. AC Power. PS. POWER AMPLIFIER TYPES. Vacuum Tube High impedance – high voltage – danger! Tuned network – PI – 3:1 VSWR – No Coupler

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POWER AMPLIFIERS

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  1. 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 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 ?

  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 • 400w S 8 +6 • 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 (20-15-10m) 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 !

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