[Elecraft] KX3 with KPA100/KAT100

[Don Wilhelm]

Ed and all,

It is more complicated than "build an interface".

The KPA100 and KAT100 depend on internal signals in the K2 for proper 
operation.
The first is '12CTRL' which is used to tell the KPA100 that the K2 has 
12 volts present.
Second is '8R' which tells the KPA100 that the K2 has been put into 
transmit.
I will admit that those 2 above could be 'dummied up' by a 12 volt "ON" 
switch and 'PTT'.  But there are other critical signals that are not 
possible except with the K2 base.

The first of those is the 'AUXBUS' which is necessary for the KPA100 and 
KAT100 firmware to operate.  This 'one wire' signal is the main signal 
to communicate among the various firmware processors in the K2 system. 
It includes band data as well as PA temperature, fan state, current 
indication, fan speed control, control of the KPA100 T/R state, TUNE 
power and KAT100 tuning control, detection of actual power output over 
the VRFDET line so the K2 firmware can control the power output.  It is 
also necessary to calculate the SWR as well as measuring the actual 
power output and feeding that information to the base K2 firmware for 
drive power control.

Those latter signal lines would be quite impossible to drag out of a 
KX3, yet they are essential to the proper operation of the KPA100/KAT100.

If one were to redesign the hardware and firmware of the KPA100 and 
KAT100, it may be possible to run them as a standalone amplifier and 
tuner, but given the magnitude of the task, selling the KPA100/KAT100 
and using the money to buy a KXPA100 and KXAT100 would be the best way 
to make a 100 watt system for the KX3.

73,
Don W3FPR

On 1/25/2020 2:41 PM, Edward R Cole wrote:
> At first I read KXPA100, not KPA100.  Of course the KXPA100 was designed 
> to be a companion  to the KX3.
> 
> I have one and drive it with either my KX3 or K3/10 (10w version of the 
> K3).
> 
> I suppose one could build an interface from KX3 to KPA100.  Basic need 
> would be PTT, RF drive, and Band switching.
>