OpenBCM V1.06 (Linux)

Packet Radio Mailbox

ED1ZAC

[C.D.G. OpenBCM]

 Login: GUEST





  
G8MNY  > TECH     24.06.19 11:00l 47 Lines 1985 Bytes #7 (0) @ WW
BID : 9563_GB7CIP
Read: GUEST
Subj: DC/RF Sensing PA Switching
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 190624/0849Z @:GB7CIP.#32.GBR.EURO #:9563 [Caterham Surrey GBR] $:9563_GB
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, but 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 & passes any DC to turn on TR1. TR1 turning on charges up the
22uF & makes TR3 initially conduct to give fast Tx attack. When 22uF is over
2V TR2 is turned on & 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 & 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


 27.06.2019 12:03:28lGo Back Go up