[Elecraft] BCD voltage

[Don Wilhelm]

Al,

What are you using to determine the 3 volts?  The Band Data output lines 
are pulled up to 5 volts by a 2.2 kohm resistor.  If the device you are 
measuring with has a load of 3.3k, the voltage measured would be 3 volts.

BTW - the switching level for TTL (or CMOS) is +1.5 volts, so 3 volts 
will be interpreted as a high level with no problem (and plenty of noise 
margin).

Typically the low level is the one that causes problems - check to be 
certain the voltage for the non-active band data lines is 0.5 volt or less.

73,
Don W3FPR

Alfred Frugoli wrote:
> Hello,
>
> I'm working on wiring up a band decoder to the ACC port on the back of the
> K3.  I'm seeing 3V when a BCD pin is active.  The rig is SN 4094.  The
> manual says that "older" rigs may need a pull up resistor.  I wouldn't have
> thought that a brand new out of the warehouse rig would have been an "older"
> K3.  Am I missing something?
>
> Thanks.
>
> 73 de Al, KE1FO
>   
>