11
Unable to Hold Repeater While Transmitting:
The most common cause is a weak signal. But if
you are sure you are in an area where your signal should be strong at the repeater, over deviation
may cause the repeater to shut off. Check with the repeater operator to determine the proper
deviation for your voice and for the PL tone or tone burst (if used). If needed adjust the KX3
deviation as described under
Frequency Deviation
on page 6. Note that there are separate
adjustments for voice and PL or tone burst deviation.
Wattmeter:
The wattmeter is calibrated at the factory. If you feel you have a more accurate low-
power VHF wattmeter or spectrum analyzer and an accurate VHF 50-ohm dummy load, you can
adjust the wattmeter calibration. To adjust the wattmeter, hold
M E NU
and then turn the VFO
knob to
WMTR XV
(transverter wattmeter). Note the default value in case you decide to return to it.
Hold
KHZ
until
UNLOCK
appears briefly in the VFO B display area and turn the VFO knob to
change the wattmeter reading. Turn the knob counter-clockwise to increase the power output or
clockwise to decrease the power output. Transmit to see the change and repeat as needed. The
wattmeter displays the average power output on 2 or 4 meters rather than displaying peak output as
it does on 160 through 6 meters. Use a steady carrier to adjust the calibration.
Circuit Description
The KX3-2M transverter operates at an I.F. frequency in the 48 MHz range while the KX3-4M transverter
operates at an I.F. frequency in the 23 MHz range.
J1 connects the I.F. signals to the KX3. The IF signal passes through a low-pass filter to a CMOS SPDT
switch.
When transmitting, the CMOS switch passes the I.F. signal through an attenuator (approximately 25 dB).
The attenuator allows the KX3 to operate at drive levels high enough to provide accurate power metering.
The CMOS switch bypasses the attenuator when receiving.
A high-performance double-balanced mixer converts the I.F. to the 2M or 4M band using a local oscillator
signal supplied by the KX3 via J4. High-side injection is used on 2 meters, so when the KX3 VFO is set to
144 MHz indicated on the display, the local oscillator frequency is 192 MHz to produce an I.F. frequency
in the 48 MHz range. Similarly, high-side injection is used on 4 meters (70 MHz) to produce an I.F.
frequency in the 23 MHz range.
Another single-pole double-throw CMOS switch connects the mixer to the transmit or receive signal path.
In transmit mode, the signal passes through three stages of amplification and then on to the antenna
connector J3 through a diode antenna switch and a low-pass filter.
The diode antenna switch uses two diodes connected so that when one is forward biased to pass the signal,
the other is reverse biased to block the signal. Switching the bias connects the antenna to either the transmit
or receive signal path.
In receive mode, the signal from the antenna connector is routed through the antenna switch to a low-noise
amplifier and then through the single-pole, double throw CMOS switch to the mixer.
The mixer converts the incoming signal to the I.F. and passes it directly to the next CMOS switch,
bypassing the transmit signal attenuator, and then on to I.F. connector J1.
