| |
G8MNY > TECH 06.03.26 09:04l 47 Lines 1992 Bytes #60 (0) @ WW
BID : 53647_GB7CIP
Subj: DC/RF Sensing PA Switching
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 260306/0758Z @:GB7CIP.#32.GBR.EURO #:53647 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Graphics updated Dec 03)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
For PA with RF/DC sense switching (as some rigs put out DC on Tx), that used a
diode to detect any +ve signals (RF/DC) from the transceiver to operate the PA
PTT system....
The time constants are OK for SSB & FM. The 22uF can be omitted for FM only.
TR1 & 2 BC107 etc, TR3 a TIP type PNP, D1 RF diode 1N4148 etc. D2 1N4001.
Rig o)ÄÄÂÄÄÄÄÂÄÄ´ÃÄÄÄÄ> RF to Drive Relay
³ 100K _³_ 1n
³ ³ \_/ ______+12-24V
³ ³ ³D1 ³/e
³ ³ ³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄ´ TR3
³ ³ 22K ³ ³ ³\ PNP
³ ³ ³ ³ Ext oÄÄ¿ 470 ³ +Tx
³ ³ ³ ³/ PTT ³ LED ³ ÃÄÄÄÄ> Drive, O/P,
³ ³ ÃÄÄÄÄ´ TR1 ÃÄÄÄÄ´<ÃÄÄÙ ³ Bias, &
³ ³ ³ ³\e ³/ ³ Fan Relays
³ ³ === ÃÄÄ47KÄÂÄÄÄÄ´ TR2 ³
³ ³ ³10n ³+ ³ ³\e ³
³ ³ ³ === ÃÄÄÄÄÄÄ)ÄÄÄÄ150KÄÄÄÄÄÄÄÄ´
³ ³ ³ ³22u ³ ³ +ve _³_
³ ³ ³ ³ 10K ³ feedback /_\
³ ³ ³ ³ ³ ³ D2 ³
ÄÁÄÄÁÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄ
HOW IT WORKS
D1 detects RF and passes any rig DC to turn on TR1. TR1 turning on charges up
the 22uF mkes TR3 initially conduct to give fast Tx attack. When 22uF is
over 2V TR2 is turned on and passes higher base current into TR3 via a Tx LED
ensuring it is well turned on. The 150K +ve feedback ensure snap action (too
low and it may not switch off!)
External PTT earth can be put in/out on TR2 collector.
I have found it was heat sensitive, due to the sensitivity of the 1st NPN.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
