[RTTY] Re: FT1000 and optoisolators for PTT and FSK.

[WA9ALS - John]

When I ran these experiments a year or two ago, I think I tried 4n25, 4n29,
and 4n33, and none of them would key the FT-1000MPMK5.  I finally started
asking myself "Why?" and just built a nice box using transistor switches.
In fact, I don't even switch the FSK line (just the PTT) - The TxD line goes
thru a 1K resistor straight to the FSK pin - I did it that way for the MP
and now use the same line for the PROII.  In fact, the other day in a
strange twist of the morass of cables, I -UNintentionally- fed the RTS PTT
signal straight to the PTT input of the 706MKIIG!  (I brought the rig in
from the car and hooked up the cables -without- the switchbox.)  It didn't
work correctly - I can't remember the details, but I think it just worked
"backwards" - but depending on the software I was using, I could invert the
logic and then it was OK.

All this switching stuff makes for some fun mental thought and some fun
projects, but it really doesn't have to be very fancy to work just fine - an
optoisolator, a transistor, both, a reed relay, or maybe even just feeding
the signal to the input to be switched....  Now before I get chastised, I
realize that optoisolators offer a theoretically cleaner, safer switch than
a simple transistor.  However, I already have all sorts of other lines
between the computer and the rig that don't have their grounds isolated, so
I've never understood the fear of having unisolated grounds in these
switching lines.  No RFI here either.

Anyway, be safe and treat your rig nice!  73 - John, WA9ALS


----- Original Message ----- 
From: "Doug Faunt N6TQS +1-510-655-8604" <faunt at panix.com>
To: <wa9als at starband.net>
Cc: <rtty at contesting.com>
Sent: Friday, June 20, 2003 9:13 PM
Subject: FT1000 and optoisolators for PTT and FSK.


>
> I've been cogitating on this for a bit.  I've now had it pointed out
> that a 4N25-type optoisolator should pull the PTT and FSK lines down
> closer to ground thn a 4N33-type.  The difference is a simple
> transistor output rather then a Darlington pair.
>
> If someone with the appropriate radio could try this all out, I'm sure
> the result of the experiment would be interesting to us all.
>
> They are plug-compatible, so if your optocoupler is in a socket, you
> can just switch them in the socket.
>
> 73, doug
>