23
Figure 8. Antenna Tuner Matching Capability.
The ATU recalls tune solutions based on the frequency reported by an interfaced radio or by the KPA1500
frequency counter when the
KEY IN
line is held low.
This tune feature works in both
STBY
and
OPER
modes. Frequency information from the interfaced transceiver
may be used to select an ATU setting without transmitting.
Manual Tune Operation
1.
Tap
AT U T U N E
to initiate an ATU tune cycle. The ATU
IN
light will flash.
2.
Supply 10-50 W of RF from your transceiver.
Relays in the ATU operate to switch values of inductance (L) and capacitance (C) to match the antenna
impedance to a value close to 50 Ω non
-reactive for the KPA1500 or for the driving transceiver when the
KPA1500 is in
STBY
.
The
SWR
LEDs 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.
In some cases, especially with an antenna that is very sharp or narrow, the ATU may not be able to find the best
dip in SWR. In this case, tap the
AT U T U N E
again within three seconds after tuning is completed to initiate the
fine tune process. Fine tuning makes smaller L and C steps to find a suitable solution not possible with coarse
tuning steps. This may result in a lower SWR. You must not interrupt the RF from the transceiver for this
function to complete properly. Once the tuning operation is complete, un-key your transceiver.
If the SWR is 1.2 or less when a tune operation begins, the KPA1500 bypasses the matching network without
searching for a tuning solution. The
ATU IN
and the
ATU BYP
LEDs both illuminate to show the tuner is
bypassed for this frequency. When returning to the selected frequency, the internal ATU will recall the bypass
mode, and both
ATU IN
and the
ATU BYP
LEDs will be illuminated.
You can change the default bypass SWR threshold with the
ATU BYPASS
parameter in the Menu. Subsequent
ATU TUNE
attempts will use the new threshold to determine when the internal ATU is placed into Bypass mode.
