[TenTec] X-Lock-3

[N6QW]

For those who would like to see an X-Lock-2 installation in a Ten Tec Corsair I click on the link below

http://www.jessystems.com/X-Lock%20(rev%201).pdf

Basically the X-Lock is a refinement of what is called a Huff and Puff VFO stabilizer. In operation the X-lock samples the PTO or VFO frequency at a certain rate (which has some level of adjustment). A microcontroller is used to manage the sampling and to store the set frequency. If during the course of the sampling, the frequency is sensed as drifting a correction voltage is generated that is supplied to a varactor diode. The magnitude of the voltage adjusts the varactor so that more or less capacitance is effectively supplied to the tuned circuit to compensate for the upward or downward drift. This happens so quickly that the frequency appears to remain fairly static. The X-Lock 2 has additional circuitry so that when a large excursion is sensed such as you would have when you QSY, the correction circuitry is placed on "hold" for a short period of time. No phase noise is introduced into the circuit for it is merely a  correction of frequency about a set frequency using a varactor diode. 

Thus you get the idea of huffing and puffing. The X-lock in essence gives the appearance of crystal stability.  

In my Corsair I, prior to installation of the X-Lock 2, it took about 2 hours for the Corsair to stop drifting. Now I can turn on the Corsair I and after about a 2 second initialization it will stay on that frequency for hours on end. I paid less than $40 delivered (depends on the daily exchange rate) and it took about a day to build the circuit board and make the installation. Because of the way I installed it there is some impact to the Corsair I RIT control. In the wide RIT excursion the range is now about 3 kHz and was somewhat off centered. I talked to Ten Tec and there is a pot on one of the boards that can re-center the excursion so that an equal amount of offset is observed on either side of the center position. That said I think you are stuck with a smaller excursion range but it will be centered.

The X-Lock-3 just announced has added functionality beyond the X-Lock-2 for the RIT. 

73's
Pete N6QW (ex W6JFR)