Icom > KPA500 > KAT500 Faults


I've had my KPA500 and KAT500 for quite a while now.   I presently drive them with an IC-7300.

If I leave the KPA500 in OPER mode and move to an area of the band where the KAT500 needs to re-tune or pull a tune from memory, it will cause a "HIGH SWR Fault" on the KPA500.

I thought the thresholds were suppose to make it possible to send a 20w carrier to the KAT, have it tune while inhibiting the PTT line on the amplifier.  Once tuned, it would enable the PTT.

Am I understanding the operation correctly?  Any ideas what might be wrong?


Ralph McClintock

 The KPA is doing exactly what it was designed to do. You cannot leave the KPA500 in OPER when doing a Tune of the KAT500. The KPA needs to be in STBY. If you had a K3, yes, you could do that but not with other rigs. Have both IC7600 & K3 with KPA/KAT500.


I figured a couple things out and thought I would share.

First, I don't know how to pass band info from the Icom to any tuner including the KAT500.

I was having trouble interfacing it with my KAT500 / KPA500 combo.  I had tried two methods for the keying circuit.  First was via the ACC plug and the 2nd was via the provided RCA jack on the rig.   While both of these methods keyed the circuit, I still had trouble with the amp faulting unless I remembered to place it in STBY prior to tuning.

The answer was to purchase an inexpensive cable from LDG.  This is an IC-PAC-6 cable.   You can build this cable if you like but for around $12 I didn't think it was worth the effort so I purchased one.  This cable follows the AH-4 tuner standard for Icom and can be used to control many different amplifiers manufactured today including the KAT500 / KPA500 combo that have adopted the AH-4 standard. This cable essentially prevents the amp from keying while the tuner is tuning.

So now I have 3 cables between the Icom rig and the Elecraft equipment.  The IC-PAC-6 provides tune control and 12v power to the tuner, the normal key line via ACC or RCA and the ALC line.

The IC-PAC-6 allows you to press the TUNE button on the front of your Icom to tune the KAT500.  When you press the TUNE button on the rig, it will tune the KAT500 but NOT key up the amplifier. The amp can remain in OPRATE mode while you press the tune button on the rig.

This is great!  No more placing the amp in STBY, no more changing the mode to AM and pressing the mic button while the tuner tunes and placing the amp back into OPR and rig back in SSB when done.   Just press the TUNE button on the rig and wait a second.  DONE!


Mitch Winkle - AB4MW

The Key line from the radio should go to the KAT500 first, and then "daisy chained" to the KPA500.  Thus the KAT controls the KPA for bypassing the amp while tuning.

Bob McGraw - K4TAX

This is shown on page 6, figure 2 of the KAT500 manual.  See note #5 in that regard which is explained in detail on page 7. 

Bob, K4TAX