[Elecraft] [KAT500] Cabling Diagram

[Richard Ferch]

Roy,

Why are you using the figure on page 6? That is only needed if you have 
an external device that controls the key line (the box at the top right 
corner in the figure on p.6). If you don't have such a device, the 
applicable configuration is the figure on p. 4. With only the K3, KPA500 
and KAT500 you do not need to use the RCA cables at all, because PTT 
control is already provided on pin 10 of the DB15 cables.

If you do have an external device that needs to have PTT control (the 
box in the upper right corner of the figure on p.6), you must use the 
key line interrupter in the DB15 line to allow the external device to 
control PTT (see note on p.5). Without the key line interrupter, the PTT 
will be switched by the DB15 cables without regard for what the external 
box requires.

I am using the connections from p.4 (no RCA cables), and it is working 
fine, with a couple of caveats.

First, and from your description I suspect this may be your problem: 
Although I had used CONFIG:TUN PWR = 25 in the K3 with the KPA500 off in 
order to "train" the KAT500 for my antennas on all frequency segments, 
once I was finished the initial training process I had to set CONFIG:TUN 
PWR back to NOR before using the KPA500. The reason: On some bands, TUN 
PWR of 25W is too much drive for the KPA500, so if I held the XMIT 
button on the K3, i.e. used TUNE on the K3 with the KPA500 in OPERATE, 
the amp would trip on those bands. Make sure the TUN PWR on your K3 is 
either set to NOR, or else is set lower than the lowest driving power 
you use with your KPA500 on any band, in order to avoid tripping the amp 
on bands that don't require high driving power.

The other caveat is to wait for a second or so after switching either 
the band or Operate/Standby on the KPA500, to allow everything to 
settle. If you change from standby to operate and start transmitting too 
quickly, the K3 may not have had time to react to the operate/standby 
signal from the KPA500 and change its power level before you start 
transmitting.

You also need to have CONFIG:PWR SET on the K3 set to Per Band in order 
for power control of the K3 by the KPA500 to work properly.

73,
Rich VE3KI

Roy Morris wrote:

> I have connected the cables as shown on page 6 of the KAT500 Automatic Antenna Tuner Owner's Manual, revision B3, November 20, 2012. I am connecting the K3, KPA500 and KAT500 using the DB15 interface cables and the two RCA (yellow end) cables for the separate key line. This diagram shows the key line interrupter inserted between the DB15 cable and the K3 ACC socket. I have not inserted the key line interrupter, and the system seems to work fine. However, I DO have to change the KPA500 from OPERATE to STANDBY when changing frequency because leaving it in the OPERATE position may cause the amp to FAULT when I hold the XMIT button on the K3. I believe the tuner is trying to search with high power. I wonder if inserting my key line interrupter would prevent this. All frequencies had been previously memorized by the KAT500. Thanks. Roy Morris W4WFB