Elecraft K60XV Manual - Manual (Page 21)

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Circuit Details
(Refer to the schematic on the next page.)
The K60XV has two distinct functions: 60 meter band-pass filtering, and low-level transverter interface.
Both are under control of microcontroller U1, which receives configuration commands from the K2 via the
AuxBus. U1 drives latching relays K1 and K2; provides transverter control outputs (keying, address
selection) that can be used with non-Elecraft transverters; and enables the transverter low-level I/O path
when it's selected by setting /LP to 0V and 6LP to 6 volts (see discussion below).
Relay K1 and associated components re-resonate the 40 m BPF on 60 meters. P2 provides the interface to
the 40-meter filter on the RF board.
The XVTR ALC circuitry acts as a compensated linear power detector. It converts a 0 dBm (1 mW)
transverter output level to about 3.6 VDC. This means the bargraph will be full-scale at 1.0 mW, with 0.1-
mW increments. Rev 2.04 K2 firmware also properly displays power in the LP case, from 0.01 to 1.27 mW
(e.g.: P 1 . 2 0 L P ).
When 6LP is low (i.e. when the low-level split-path interface is not in use), buffer Q2 (2N2222) looks like
a high impedance to VRFDET. But when the LP interface is in use, 6LP is high, powering U2, and Q2 acts
as a buffer for U2's output, allowing it to easily override the combined impedance of the K2's standard
power metering circuit and a KAT2 or other ATU if present. When the split path is in use, K2 firmware
turns off the VRFDET signal buffers on the KAT100 and/or KPA100 if present.
The circuit at upper right provides XVTR T/R control and signal routing. Normally relay K2 is reset,
looping the BPF signal back to TX IN (the input to the K2's 10W transmit strip) and AC-shunting the
transverter RF path to ground. If the operator switches to a transverter band configured for low-level I/O,
K2 is set. This AC-grounds the input to the 10W PA strip (K2A) and routes the BPF output signal to the
XVTR TX and RX PIN diodes, D2 and D1 respectively. At the same time, the MCU (U1) grounds the /LP
signal (U1-3 is an open-drain output), allowing D1 or D2 to be forward biased.
In RX mode, 8R is high, forward biasing D1; in this case switch Q1 (2N3906) is open, and D2's anode is
held at 0 V by R10 (near the bottom of the sheet). In TX mode, 8R is near 0 V, turning on Q1 and placing
6V on the 6T line. This turns on D2, while D1 is now reverse biased. Also in TX mode, Q3 (2N7000) turns
on. The drain of Q3 is routed to pin 2 of J2.
The low-going TX signal at pin 2 of J2 could be used with non-Elecraft transverters to do transmit keying.
Elecraft XV Series transverters have a connection to the 8R line for keying purposes. The logic-level
outputs on J2 represent the binary value of the ADR parameter in the TRNx menu entries. These signals
could, with proper buffering and RF bypassing, be used to turn transverters on or off. XV Series
transverters obtain their physical address via the AuxBus, so these connections are not needed.