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G8MNY > TECH 30.09.18 08:35l 87 Lines 4266 Bytes #999 (0) @ WW
BID : 40111_GB7CIP
Read: GUEST
Subj: PSK31 interface isolation
Path: IW8PGT<IR2UBX<DB0RES<DB0ERF<OK0NAG<OK0NBR<SV1CMG<ON0AR<GB7CIP
Sent: 180930/0729Z @:GB7CIP.#32.GBR.EURO #:40111 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Nov 09)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
________________________________________________________
³ ŚÄÄÄÄÄÄÄÄæ ŚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄæ == == == ³
³ ßßßß == ³ \ ³ ³ Rx 14.273.5 vfo A 12³ _ _ ³
³ /~\ ĄÄÄÄÄÄÄÄÄŁ ĄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄŁ (_) (_) ³
³ \_/ ____ IC-735 ³
³ ßßß ~~~~~~""""""~~~ /' `\ ßßß /"~"\ [] ³
³ 0 ÜÜÜ |(~) | ÜÜÜ | | ³
³ Ž Ž Ž Ž Ž Ž ³ ~ ³ \._./ [] ³
³ /~~\ ßßß Ž Ž Ž Ž Ž Ž | | ßßß == == == ³
³ \__/ ÜÜÜ # # # # # # [] \.____./ ÜÜÜ [___] [___]³
ĄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄŁ
Having just got going on this mode with an IBM Laptop & ICOM IC735. I was
concerned about damaging either with a direct connection!
This applies to all modes like RTTY SSTV AMTOR etc, where a PC/RIG is connected
to anything with medium to high DC current supply with a different earth or has
RF currents!
So I have made an isolated barrier TO PROTECT THE LAPTOP's SOUND CARD FROM
R.F.I. & getting ZAPPED & also the Rig from the Laptop's RF QRM. As well as
doing that it also STOPS any HUM LOOPS & DAMAGING DC PATHS the can also burn
out RIG's MIC/LS & the PC interfaces!
For this rig it gave a nice 1 plug solution...
LAPTOP ICOM IC735
PNP ______________ Pin 3
___ 1 OPTO 5 ³/e ³ PTT A
RTS 7 oÄÄ1kÄ)___)Ä2k2ÄÄĀÄÄÄÄæ ŚÄÄÄÄ´ _³_1N4001
RS232 9 pin ³ ³ 1N_³_ _³_ ³/ ³\ /_\ U
GND 5 oÄÄÄÄÄŁ ³ 4148/_\ \_/š ´ ³ ³ Ground
ĄÄÄÄÄÄÄĮÄĀÄÄŁ ³\e______³___³_________ Pin 2 X
³ 2 3 ³ Screen
___ ³ ³ 1
LS Tip oÄ8RÄ)___)ÄÄÄÄÄÄÄÄ)ÄÄæ ŚÄÄÄÄ)ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Pin 4
Jack 3.5mm ³ ³ ³ )||( ³ Mod Input
Sleeve=ÄÄÄŁ ³ ³ )||( ³
³ ³ )||( ³ ÄÄÄÄ ĄÄÄÄÄ´ ___ ³ ³ ³ ³ )||( ³ V ³_³ Rx Jack G
ĄÄÄÄÄÄÄÄĮÄÄÄŁ ĄÄÄÄÄĮÄÄÄÄÄÄÄÄÄÄÄŁ 3.5mm
small 1:1 signal
transformers
Of course for other Rigs with different pinouts etc. refer to handbooks.
TRANSFORMERS
They need to be low capacitance primary to secondary & could be from scrap
modems/answering machines etc. about 10mm cube in size. A 1:1 ratio is not that
important as lnsformer.
TX PTT
The Rproected by aries 1k in the plug to reduce t
___ 1 OPTO 5
RTS 7 oÄÄ1kÄ)___)Ä2k2ÄÄĀÄÄÄÄæ ŚÄÄÄÄÄĀÄÄÄĀÄ PTT
RS232 9 pin ³ ³ 1N_³_ _³_ ³/ ³ ³
GND 5 oÄÄÄÄÄŁ ³ 4148/_\ \_/š ´ ³ ³ But the Opto & NPN
ĄÄÄÄÄÄÄĮÄĀÄÄŁ ³\e ³/ _³_ may be less RF immune
³ 2 3ĄÄÄÄ´ /_\ in this arrangement.
³\e ³ Gnd
ĄÄÄÄĮÄÄ
There are many types of opto isolators most should work OK onceare found.
SERIES Rs
A good idea but not essential is to copy the series R in the plug at the PC end
if you can, as this does stop some RF & excMICSOCKET
If you using a mic socket (r line) for the input either on the laptop
or the rig, you will need an attenuator ideally in the mic plug so that RF+hum
pickup are attenuate 1k Plug ill need
Screen ÄÄÄÄÄÄÄÄĮÄÄÄGnd o be small.
Inside mic plug
BOXING UP
The whole lot is mounted on stripboard, & housed in a small plastic box making
sure the 2 sets of leads are kept away from each other.
IN USE
With a local aerial, this simple isolation significantly reduces the QRM
compared to a direct connection.
With a small nearby SW PLL SSB Rx with a small whip aerial it produces a good
demonstration of the mode & n G8MNY @ GB7CIP
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