[Elecraft] [K3] K3 driving KK1L band decoder

[Greg]

As Joe mentioned you will need to do the pull up resistor update for
this to work.

I run a splitter cable off the ACCY port on the K3 with one side going
to my Quadra amp and the other side to the KK1L board.  Due to the
different impedences between the two it did not work (driving one by
itself was fine...but not both).  I had to add a buffer circuit
between the ACCY output and the band decoder input.  Once I did that
the KK1L board worked great with the K3 connected to the Quadra at the
same time.  I don't recall what IC I used but it was easy to
get...think I got it at radio shack.
If you are only going to be connected to the band decoder you should
not need the buffer.

73
Greg
AB7R


On 9/6/12, Joe Subich, W4TV <lists at subich.com> wrote:
>
> The PS2501-4 in the inputs of the KK1L band decoder are opto isolators.
> Pull up resistors will be required in the K3 in order to provide drive
> to the LEDs in the optos.
>
>> My KK1L board (built in 2006) seems to be loading down the K3 band
>> outputs.
>
> The K3 band data outputs are open drain - they can not be "loaded
> down" as they do not source voltage.  Note:  the KK1L design uses
> 3K3 Ohm series resistors to limit current to optos.  Depending on
> the sensitivity (current transfer ratio) of the PS2501-4 you may need
> to reduce the resistance of those resistors in order obtain enough
> current through the LED.
>
> 73,
>
>     ... Joe, W4TV
>
>
> On 9/6/2012 12:05 AM, Ethan Miller K8GU wrote:
>> Is anyone else running a K3 with a KK1L band decoder?  The K3 manual
>> states that "earlier K3s may require external pull-up resistors to 5
>> vdc."  Did you need to do this?  My KK1L board (built in 2006) seems
>> to be loading down the K3 band outputs.  Before I add the pull-up
>> resistors, I just want to make sure that this isn't a sign of
>> impending doom...
>>
>> Thanks and 73,
>>
>> --Ethan, K8GU/3.  (K3 S/N 6714, TS-930S S/N 5010245)
>>
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