[1000mp] Computer Interface

[Bob Warren]

Hi Doug
Sounds as if your optoisolators can not 'sink' the current on the PTT line. 
Select another isolator with a higher Icmax.
Bob W2ZXQ
----- Original Message ----- 
From: "Doug Rehman" <k4ddr at earthlink.net>
To: "'All about Yaesu 1000mp'" <1000mp at mailman.qth.net>
Sent: Sunday, August 28, 2005 10:45 PM
Subject: [1000mp] Computer Interface


>I just finished building an interface for my Field for both CW and digital
> modes. I used the circuit found at http://www.qsl.net/wm2u/interface.html
> for both the CW key and the PTT. The CW key works perfectly from the
> computer, but I am having a problem with the PTT line. The PTT line is
> connected to Pin 3 of the "Packet" connector.
>
> When keyed by the computer, the PTT voltage drops from 13.4 volts to about
> 2.7 volts- not enough to key the radio. If I parallel 50 ohms across the
> opto isolator's output, it works like it is supposed to (the standby 
> voltage
> on the PTT line drops to about .7 volts, but the radio isn't keyed until 
> the
> computer keys it).
>
> I've tried to use the CW key output for PTT, but it does the same thing so 
> I
> don't think it's a wiring or component issue.
>
> I've also checked the ground connection- no problem (.1mV difference
> according to my DVM).
>
> It won't key the radio from the  PTT connector on the back either.
>
> I've used this exact same circuit before on a Kenwood TS-430S and TS-2000
> without any problems.
>
> Any ideas? Anybody experienced this before?
>
> Hanks,
> Doug
> K4DDR
>
>
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