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G8MNY > TECH 27.03.20 11:52l 60 Lines 2360 Bytes #999 (0) @ WW
BID : 50078_GB7CIP
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Subj: Using 2 HF PAs
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Sent: 200327/0947Z @:GB7CIP.#32.GBR.EURO #:50078 [Caterham Surrey GBR]
>From g8mny%gb7cip.#32.gbr.euro@i0ojj.ampr.org Fri Mar 27 10:50:16 2020
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Aug 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
At an 8 day Ham Summer Camp I needed to use 1 of 2 HF PAs for /P. One was a
500W Transistor PA floated on a large battery that allowed just a small petrol
650W generator to keep the batteries topped up, & the other was a Valve Amp
used in the colder nights & that needed much bigger generators (2.3 / 7kW).
I looked at the 2 possible connection systems...
FULLY SWITCHED SERIES RF & TEED CONTROL LINES
ÚÄÄ¿
ÚÄÄÄÄÄ´HF³ ÚÄÄ¿ ÚÄÄ¿
ÚÄÄÄ¿__/. ÚÄÄÄ´PAÃÄ¿ ÚÄÄÄ¿_________³HF³_____³HF³ ÚÄÄÄ¿
³HF ³RF : ³ ÚÄ´1 ³ ³ ÚÄÄÄ¿ ³HF ³RF _____³PA³ ___³PAÃÄ´ATUÃÄ
³ ³____/. ³ ÀÄÄÙ \__³ATUÃÄ ³ ³___³ ÚÄ)Ä´1 ³ ³ ÚÄ´2 ³ ÀÄÄÄÙ
³Rig³PTT: : ³ ÚÄÄ¿ ³ ÀÄÄÄÙ ³Rig³PTT ³ ³ ÀÄÄÙ ³ ³ ÀÄÄÙ
³ ³______/..³HF³ ³ ³ ³_____³ ÀÄÄÄÄÄÄÙ ³
ÀÄÄÄÙALC: :...³PAÃÄÙ ÀÄÄÄÙALC ÀÄÄÄÄÄÄÄÄÄÄÙ
:.....³2 ³
ÀÄÄÙ
The switched system is complex unless relays are used.
The series & teed system assumes PA2 can handle PA1 Tx power in through mode!
Steering diodes my be needed to isolate the powered off PA from affecting PTT &
ALC lines...
Ú´<ÃÄÄPA1 PTT Test PTT interaction by keying up
PTTÄÄ´ Tx + PA & seeing if connecting the
À´<ÃÄÄPA2 PTT unused PA has any affect on Tx/Tx.
Add diodes if there is any affect.
Ú´>ÃÄÄPA1 ALC Test ALC interaction by setting Tx
ALCÄÄ´ + PA to 100W & adding the turned
À´>ÃÄÄPA2 ALC off PA. I found no power change so
steering diodes were not needed.
Of course NEVER enable both PAs together!
See my Tech bul "T500 M 12V 500W HF Linear", "PTT line for Drake L-4B PA", &
"ALC line for Drake L-4B PA".
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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