Elecraft KAT500 Owners Manual - Manual (Page 19)

16
Tune Operation and Memories
Tune Operation
A tune operation begins when RF power between 7 and 100 watts is applied and the SWR is above the
tuning threshold in
AUTO
mode, or when the
TUNE
switch is tapped in either
AUTO
or
MAN
modes. The
RF power must be below the key line hot switching limit (see Key Line Hot Switching, above) so the
KAT500 can disable the amplifier. The KAT500 will not respond to less than 7 watts of drive and over
100 watts will cause a fault condition (see Fault Conditions on page 18)
Relays in the KAT500 operate to search for values of inductance (L) and capacitance (C) that match the
impedance of the antenna to 50 ohms non-reactive for the transceiver.
The SWR lights indicate how close the antenna impedance is matched to the transceiver. The L and C
values switched in will provide a good match for most situations, but if you feel the resultant SWR is high
you can tap
TUNE
again within 3 seconds to initiate a second, fine tuning process in which smaller
changes in L and C values are tried. That may result in a lower SWR. You can also manually adjust the L
and C values using the KAT500 Utility Program (page 20).
If you have a high-Q (narrow bandwidth) antenna that benefits from a fine tune operation on certain
bands, you can configure the KAT500 to automatically do a fine tune operation without pressing the
TUNE
switch again with the Utility Program (see Auto Fine Tune, page 21).
If the SWR is below 1.2 when a tune operation begins, the KAT500 bypasses the matching network. The
KAT500 remains in either
AUTO
or
MAN
mode but the matching network is bypassed (switched out of
the RF path). The matching network also will be bypassed (switched out of the RF path) if the SWR
provided by the tuning solution is less than the SWR with the matching network bypassed. The bypass
setting will be stored as the tuning solution so the matching network will be automatically switched out of
the RF path you return to that frequency segment as described under Memories below.
Memories
After successfully tuning, the KAT500 stores the L and C settings or the bypass setting in memory. They
will be recalled almost instantly when returning to that frequency later. The entire spectrum from 1.8
through 60 MHz is divided into frequency segments and tuning information is stored for each segment in
which you have successfully completed a tune operation.
When starting a tune operation for a frequency segment that has no previously stored L and C values, the
KAT500 first tries the settings in the nearest frequency segment that has tuning data.
Since retuning is normally required over a narrower frequency range on the lower frequencies to maintain
a low SWR, the lower frequencies have narrower segments assigned as follows:
 Below 3 MHz the segments are 10 kHz wide.
 From 3 MHz through 26 MHz the segments are 20 kHz wide.
 From 26 MHz to 38 MHz the segments are 100 kHz wide.
 From 38 MHz to 60 MHz the segments are 200 kHz wide.
The KAT500 also stores the antenna output that you selected for each band.