I have owned a DB6NT MKU 23G2, built as a kit for many
years now and have been satisfied with itrs overall performance. Having recently
acquired a GR1236 noise meter and an SDRIQ I needed to investigate extracting a
144MHz receive only signal to drive a 144/28MHz converter to use these units
without needing a separate 2304/144MHz receive converter. Initial examination
revealed that a signal could be tapped off from the slider of the RX gain
pot. A small terminal pin was inserted alongside the pot and a 1nf chip
capacitor connected to it on the track side of the board. A short piece of RG174
on the ground plane side of the board was connected to an SMC connector on the
side of the box. The opportunity was also taken to fit an SMA connector on the
sidewall near the crystal to allow for future external 120MHz oscillator input
The 1W 144MHz driver (the maximum drive level found not to
destroy the PIN diodes was hooked up to the common IF port and the 144MHz level
measured at the SMC connector. The level was –12dBm which could cause damage
to anything connected to the port. Thoughts were initially given to adding extra
pin diodes to increase the isolation, but there was little space and no suitable
pin diodes could be found. I then came across a PCB RF relay Omron type G4Y-152P
that was intended to have high isolation at 900MHz. This was glued upside down
to the chassis. The normally open connection was terminated with a 50 ohm chip
resistor. The normally closed connection was connected to the SMC connector on
the transverter. The common connection was connected to
an RF connector mounted on the back of the chassis to allow connection to
the external equipment. The coil was activated on transmit, thereby terminating
the independent receiver port in 50 ohms on transmit. The 144MHz level at this
point was now –75dBm, an acceptable level for the external equipment
The following shows the circuit and the finished view of the modifications. The relay is in the bottom right hand corner.