If the voltage drops when your LPT output is loaded too much by the 1k + BE
in series, you should add a something like a 4.7k in parallel the base.
This is a common problem of new pc hardware and some of the older rigs cat
output like that of the ft990.
A cheap digital voltmeter would definitely help a lot... :)
73 de Zoli HA1AG
> Hi Luca,
>
> your description of the problem is quite short. So I am not sure that
> my response would meet your problem.
>
> Some weeks ago I built one LPT-interface for CW-keying and
> PTT-control.
> First I tried this with 2 optocouplers, one for CW and one
> for PTT. But
> it didn't work correct. After some hours of "try an error" I
> discovered
> that it could be a problem for the LPT-port to supply current enough
> for the optocouplers. The PTT-pin of the LPT-port didn't switch when
> the optocoupler was connected but switched very fine when there was no
> load. So I built the interface with transistors and had to keep care
> that the resistors in the basis-lines of the transistors are big
> enough, so that the LPT-pins are not overloaded.
>
> 73 + 55
> Wolf, DL6JZ
>
> Luca IK2NCJ schrieb:
> > Dear friends,
> >
> > after I discovered that WL running under XP and 98 SE on
> > Acer laptop won't switch radio from RX to TX from LPT1
> > port, I thought that using an older laptop with a DB9 COM
> > port I can control PTT from there and send the CW carrier
> > from LPT1.
> >
> > It looks very easy solution and it is! The only thing is
> > that also COM port doesn't send PTT signal to radio!!
> >
> > Anyone with same problem??
> >
> > Luca IK2NCJ
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