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Low power output on some bands: The K4 monitors peak power,
SWR, temperature, amplifier drive level, current drain, and supply
voltage. Power output may be reduced if any parameter is out of
range. If power output is low on a given band, check the following:
(1) Supply voltage should be ~14 V as measured at the K4's DC input
jack. Voltages as low as 11.0 V may be used at reduced output. (2)
Operation into low-impedance loads may increase current drain
beyond the allowed limit. In this case power should be reduced.
NOTE: All class AB amplifiers exhibit compression at the upper end of
their power range, especially when operated at reduced supply
voltage or into a low-impedance load. Under these conditions, the K4
limits maximum drive level into the final amplifier in order to
preserve good IMD characteristics in voice/data modes and protect
the PA devices. This may be observed by the power output bar graph
reaching a peak level below the set power level.
No transmit output: (1) Make sure the K4 is not in transmit TEST
mode (TEST switch); in TEST mode, the "TX" indicator at the top of
the LCD is replaced with "TX Test". (2) If MENU:XVTR OUT Test is
set to On, output will be routed to the XVTR OUT jack instead of
ANT1-ANT3. XVTR OUT is typically used with external transverters,
with an output of up to about +7 dBm (5 mW).
Can't transmit at power settings above 10.0 watts: Check the fuse
on the KPA4 module. This is a standard 25 amp blade fuse available
from Elecraft or auto parts stores. The recommend replacement is
Elecraft E980427 (Littlefuse part number 0287025.PXCN or Digikey
F4195-ND).
Can’t transmit in CW mode: (1) Make sure the key or keyer paddle is
plugged into the correct jack. (2) You must have VOX selected (VOX
icon on) in order to use hit-the-key-to-transmit CW. The alternative is
to tap XMIT or assert PTT, typically with a foot switch. (3) You may be
in SPLIT mode, with VFO B set for a voice or data mode. Exit SPLIT or
change VFO B's mode to CW.
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