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• to pre-adjust mic or LINE IN gain prior to transmitting a signal (see
{XMTR} knob functions <MIC> and <CMP>)
• to practice sending CW off-air
• to test T/R switching of downstream equipment
ATU TUNE
If a KAT4 ATU is installed, tapping [ATU TUNE] will initiate antenna
matching, using a power level of 5 to 10 watts. This will cause the
relays on the ATU to cycle for typically 1 to 4 seconds. Matching
terminates automatically, and the resulting LC network settings are
saved per-band, per-antenna. Up to 32 LC data values are stored for
each band/antenna combination, allowing the K4 to "learn" the right
matches for your antenna system in the course of normal operation.
Usually a match will be found with an SWR of < 2.0:1. If not, try tapping [ATU
TUNE] a second time within 5 seconds; this causes the ATU to try more relay
combinations, useful for narrow-banded antennas. Extended matching can
take up to 10 seconds. However, once all antennas have been matched at
multiple points on each band, retuning will rarely be needed even for
antennas that are narrowband.
Each time you transmit, the K4 makes sure that the stored LC settings
closest to your operating frequency are used. For this reason, after you
move the VFO and transmit, you may hear relays switching briefly (~10 ms).
Note: Any HF frequency that appears outside of the ATU's segment
map can still use the ATU for matching purposes, but only one LC
setting is saved per-band/per-antenna for this purpose. (Details on
ATU band/frequency bins TBD. Most MARS frequencies fall within the
ham-band segment map.)
For info on ATU antennas, see ANTENNA SELECTION.
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