Open up the VFO
enclosure and locate the junction of emitter the resistor R404 and
capacitor C403 on the tracked side of the VFO board (PC-400/PC700)
. Very carefully solder in place the four components that form the
compensation circuit (shown in Fig.5 and Fig.6). One
leg of the 10 nF capacitor is soldered to the R404/C403 junction,
use C426's soldering tag for the other three parts. Install a
short wire from the VAR connector to the components to connect the
If required the
three-colour LED may be remotely fitted to the front panel. Find a
suitable place for the LED and connect 3 wires to the LED
connector. I mounted the LED in the (empty) hole for the noise
Connect the PWR
socket to the 13 V DC rail inside the Atlas.
That's all. If you
assembled the board correctly the device should worked straight
off on power up!
The device is an easily
applied "add-on" module and the ability to detect rapid
frequency changes during transmit and receive is a valuable
innovation. It does exactly what is published in the advertisement
and the Atlas-215x is astonishingly rock steady like a crystal
controlled oscillator. I am very enthusiastic about this X-Lock
kit and can recommend the Cumbria Designs.
installed the X-lock in an Atlas-210x. It works just fine. This
model has a different VFO circuit using two FET transistors. He
used the supplied LED "varactor" and a 2.5 pF capacitor
connected directly to the main tuning capacitor. He has also
successfully applied the same arrangement in his Atlas-350-XL.