[Elecraft] Synchronized and stable GPS phase lock for KX3, K3 and XV transverters

[Bayard Coolidge, N1HO via Elecraft]

The newer Trimble Thunderbolt requires +24VDC, but some of the
older units on E-Bay, etc. may require +5VDC, +12VDC and -12VDC,
which can be obtained from a simple/inexpensive power supply.
(I used a Meanwell NET-35B). It outputs a 10MHz sine wave (which
plugs into the K3EXREF) as well as 1pps logic signal. Trimble also
makes/made an active antenna, which I also found on E-Bay, which
is a small square about 2 in/5 cm square and has an internal preamp
powered by +5V supplied on the Thunderbolt's antenna jack. I've
been running one for about a year now, and it maintains the 10MHz
to within about 30 parts per trillion, depending on how many satellites
are regularly visible - I usually "see" 8 or 9 in south Florida and 5-6
in the mountains of western North Carolina.