[Elecraft] KXPA100 plus KXAT100

[Wayne Burdick]

W2CTX <w2ctx at yahoo.com> wrote:

> Does anyone know if the KXAT100 tuner will still work when the KXPA100
> is turned off?  Or can the KX3 use the KXAT100 as a qrp tuner?


Short answer: Yes, the KX3 can use the KXAT100 as a QRP tuner. 

Here's how the ATU and PA functions work, assuming you have the KX3 connected to the amp using the special control cable:

- With the KX3's PA MODE menu entry set to ON, the KXAT100 is used, if present, at all power levels (along with its dual antenna switch). The KXPA100's amplifier stage is automatically enabled or bypassed based on the setting of the KX3's PWR control, which acquires a range of 0.1 to 110 W. The KX3's ATU controls all apply to the KXAT100, including ATU TUNE, ANT, and the ATU MD menu entry, which changes to ATU.X MD ('X' for 'external'). Band switching at the amp tracks the KX3's band.

- If PA MODE is OFF, both the KXPA100 and KXAT100 are turned off and bypassed. (This defaults to ANT 1.) The KX3 and its internal ATU (KXAT3) can then be used, in QRP mode, as if the amp were not connected at all. The amp draws only about 1 mA in this condition--this powers circuitry that detects an auto-on command from the KX3.

The amp can also be used without the control cable. However, in this case the amp and KX3 are fully independent, meaning that band switching of the amp is done by RF sensing on transmit, drive power must be adjusted manually at the KX3, and the KXAT100 must be set up using the KXPA100's front panel controls.

73,
Wayne
N6KR