Elecraft KPA100 Manual - Manual (Page 56)

56
Using the K2/100 at High Power
Power Supply
Dual-Supply Capability
There are two DC input jacks on the K2/100: a low-current DC barrel jack
on the lower rear panel, and a high-current Anderson Power connector on
the upper rear panel (KPA100). The low-current DC input is for a 4 amp
(minimum) power supply that can power the K2/100 in QRP mode (up to
15 W). The high-current input is for a 20-amp power supply that allows
operation at up to 100 watts.
If a high-current supply is connected, you can still connect an emergency
backup power supply or battery at the low-current input. If the high-
current supply fails, the K2/100 will immediately drop into bypass mode
and continue running from the backup supply.
Two special status messages are provided in the case where two supplies
are connected. If you turn off just the high power supply, you'll see NO
P A P S
(may take up to 10 seconds due to slow decay of the power
supply voltage). If you turn the high-power supply back on, you'll see PA
PS ON
. The K2/100 will go in and out of bypass mode when the high-
current supply is turned on and off.
High Current Power Supply Requirements
The high-current power supply should be rated at 20 amps or higher.
Switching supplies are compact and inexpensive, but generate noise that
may be heard in the ham bands if you use wire antennas with little or no
feedline. If noise is a problem, use a linear supply.
The DC input jack on the KPA100 assembly, J3, is not switched. This
means that 12-14VDC will appear on the KPA100 board anytime your
high-current 20A supply is turned on. This is typical of most compact HF
transceivers, and should not present a problem. The current drain from
this power supply with the K2 turned off should be very low.
CAUTION: Keep the K2/100 at least 18" (0.5 m) away from all
equipment that uses large power transformers. AC hum from
transformers may cause modulation of the transmitted signal that
can be heard on the air.
Antenna
Transmit/Receive Antenna Jacks
The K2/100 has two transmit/receive jacks: a BNC jack on the lower rear
panel, and an SO239 on the upper rear panel (KPA100). The BNC
connector is provided with the basic K2 for use at up to 15 watts. The
SO239 is the standard connector for higher-power operation.
If the KPA100 is installed, you should use only the SO239 antenna
jack. The BNC antenna connector should be kept covered by the
supplied rubber cap.
Receive Antenna
If you have the K160RX option installed, you'll have a separate receive
antenna jack (BNC) on the lower rear panel. This input can be enabled on
a per-band basis using the RANT menu entry.
Ground
A ground thumbscrew is provided on the upper rear panel (KPA100).
Antenna and Antenna Tuner Considerations
The K2/100 can be used with coax-fed antennas or antenna tuners. In
either case, SWR should be kept as low as possible. High reflected power
(caused by high SWR) will result in an automatic reduction of power
output by the transceiver. This is required to protect the power transistors.
When the K2/100 reduces power due to high SWR, you'll see the message
H I R E F L
on the K2's LCD.