[Elecraft] DIGOUT1

[wayne burdick]

On Jun 10, 2009, at 3:18 PM, van fair wrote:

> Wayne I am building a coax relay to be activated using the DIGOUT1 
> contacts.  I want the contacts to ground the base of a PNP transistor 
> TIP 42 through a series 800 ohm resistor.
>
> I now have a cable for the 15 pin plug with connections to pin 5 and 
> 11. When DIGOUT1 is turned to ON  on 20 meters  I get a 220 ohm 
> resistance  between pin 11 and 5. I expected to get a short  between 
> them and to ground.  Will this 220 ohm resistance in series with the 
> 800 resistor in my switch be capable of causing the transistor to 
> swamp causing the emitter and cathode to connect and go to ground to 
> enable the 12 volt relay coil.

Hi Van,

The 220-ohm resistor is in series with the open-drain control line to 
ground on the KIO3. KIO3 outputs are protected with R-C filters. This 
will add to the 800 ohms, in practice, so you'll really have 1020 ohms 
to ground. My guess is that the PNP transistor will still do what you 
expect. You could drop the 800 ohm resistor to something smaller if 
necessary.

73,
Wayne
N6KR

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