[Elecraft] Kpa 500 problem when auxiliary cable connected ...

[Eric Swartz - WA6HHQ, Elecraft]

The KPAK3AUX cable also switches the KPA500 band prior to transmit when you 
change bands on the K3/K3S. If the cable is not present, the amp will still 
change bands instantly upon transmission from any rig by measuring the 
frequency, including the K3/K3S. Either method works well.

The KPAK3AUX cable also contains the AMP KEY signal, eliminating the need for 
the RCA PTT cable.

If the KAT500 is also connected via the aux cables between the K3/K3S and the 
KPA500, them KPAK3AUX sends frequency information from the K3 to the ATU to 
select sub-band tuner segments prior to transmission.

The KAT500 will also interrupt the AMP KEY line in the KPAK3AUX cables during tune.

73,
Eric
/elecraft.com/
---
On 8/15/2016 10:39 AM, Jim Brown wrote:
> On Mon,8/15/2016 10:28 AM, Don Wilhelm wrote:
>> Are you attempting to use the band decode lines on both the Icom and the K3 
>> at the same time?
>> That will cause problems unless there is some kind of isolation provided. 
>
> And remember that the KPA500 does NOT need band information from the rig -- it 
> reads frequency with a short burst of RF and switches to the right band. So 
> does the KAT500. Just hit a dit or tap the mic. The only interconnection that 
> is NEEDED is the AMP KEY line.
>
> The only thing that a full AUX cable adds is that it allows you to push 
> buttons on the KPA500 to make the K3 change bands. I don't use an AUX cable, 
> just RCA-RCA for AMP KEY. During contests, I do that with N1MM. Outside of 
> contests, I use the rocker band switch on the K3.