I am pleasantly surprised by the response of two distinguished contest
program writers! K1EA might take a bit longer :-)
My worst hamradio frustrations in 60's were with arcing power amplifiers at
the beginning of CW TX. I use PTT, no annoying full BK. Sorry for few
seconds of occasional QRM...
Pin 1 might be better used for stereo/mono switching in SO2R environment but
that is another question concerning M$ OS XP and NT limits to LPT access.
I am glad this discussion takes place at Writelog reflector after a nice
W5XD article explaining his common sense approach to program changes.
MX & HNY & 73 de Mario, S56A, N1YU ( STROBE=PTT)
----- Original Message -----
From: "Tree N6TR" <tree@kkn.net>
To: <artinian@siol.net>; <k8cc@mediaone.net>; <TOMK5RC@aol.com>;
<w5xd@writelog.com>; <writelog@contesting.com>
Cc: <kwolff@charter.net>; <tree@kkn.net>
Sent: Sunday, December 23, 2001 6:34 AM
Subject: Re: [WriteLog] 10.69 Fixed the LPT Pin 16 Problem
> > I always assumed that K1EA used pin 1 (strobe) for the emitter of the
> > keying transistor because the state of pin 17 (CW out) is unknown when
the
> > computer is started. I'm not sure if this is a random condition or a
BIOS
> > issue, but on many computers pin 17 is high when booted which causes a
CW
> > radio to go key down (very annoying). By keeping pin 1 unasserted, the
> > logging program can prevent keying until the pin 17 is low. Indeed, if
I
> > recall correctly early versions of CT keyed only pin 1.
>
> I had always assumed the same thing - or perhaps someone was having
problems
> with a leaky transistor, and this was a way to keep it off. However, the
> "no CW" at power up is nice.
>
> > Some years later, N6TR introduces PTT control on pin 16. This pin has
the
> > same problem as pin 17 - an undetermined state at startup. To prevent
> > unintentional PTT assertion at bootup, an duplicate of the CW keying
> > circuit was used. However, since pin 1 has to be shared now, it can't
be
> > keyed for CW so positive keying on pin 17 is introduced.
>
> Yes - I think I actually "or'd" the PTT signal into the Pin 1, so that
> you could have the same "no key" on boot feature.
>
> > I've always been concerned about the current handling capacity of the
> > circuit connected to pin 1. This was designed as a ~STROBE signal to a
> > printer, now we hang CW keying circuits and PTT on it. The CW line is
> > almost certainly low current, but who knows about PTT? You never know -
> > with certain radio types that line might directly pull in a relay coil.
>
> Yup - this can be a problem - and I have found some computers just can't
> handle the current.
>
>
> > In most of my CW interfaces now I've added a CMOS logic IC to allow pin
1
> > to inhibit the CW keying and PTT in the signal path. The output devices
> > interfacing to the radio can sink directly to ground without the
currents
> > going into the LPT port. One added advantage is that the key-down
> > saturation voltage is lower, thus ensuring full power out on CW. (Don't
> > laugh - I tried to use a Darlington output optocoupler to key/PTT one of
my
> > radios and it would not work!).
>
> I have essentially done the same thing. I just put a double inverter on
> pin 1, and use that to sink the current in the emitters.
>
> > BTW, CW out has always been pin 17, not 16. Pin 16 is PTT. This is the
> > way NA has been for years and I've just been copying everybody. I just
> > checked this against a reasonably recent TRLog manual.
>
> Yup. I am the one who added the PTT as Dave says, and I tried to do it
> in such a way that everyone else could copy it. I was trying to seel TR
> Log to W3LPL once, and I guess he was impressed enough with the PTT
concept
> (which I think is really an important thing that most people don't know
> they need) that he got Ken to add it to CT?
>
> > Not to embarrass anyone, but you can't count on WX0B to get the pins
> > right. He got his NA pinouts second hand and they were incorrect (Jay
told
> > me this).
> >
> > Jeez...I thought we had all settled on a standard :-(
>
> I think we mostly have. No harm in making the STROBE go low during PTT in
my
> book.
>
> Tree
>
>
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