59.5MHz Variable Crystal Oscillator GW4RWR

Introduction
For the limited bandwidth required for SSB on 70MHz, a VXO is an easier approach than a VFO mixed with a crystal oscillator. There’s also negligible drift from switch-on with a VXO.

The VXO uses a x4 multiplier scheme to reach the 59.5MHz required with a 10.7 IF.
Relay switching selects between 14.856, 14.882 and 14.91MHz crystals, which are soldered under the board. Each crystal pulls ~25kHz. I don't know how much phase noise is introduced by this much 'pulling', it must be significant.

Implementation
The 2mm aluminium 'case' was originally a frame to support dummy loads in a CDU C+ duplexor. The voltage regulator is bolted to the outside of the case. Only one section of the variable capacitor was needed, and it's rotated via a 6x reduction drive. A resistor splits less than 1mW to the exciter board, and 10mW toward the receive board, via SMA sockets.

A reverse biased red LED provides RIT/XIT. That gave only +-400Hz shift. Swapping for a proper varicap gives +-1.5KHz shift.

Commentary
I should have left space for a fourth relay, as I've since found other crystals that could extend the range. I would also have liked to be able to switch in a non-VXO 'FIXed' crystal, for instance to select the calling frequency. Interestingly, the crysals I've used were engraved with airband frequencies, since 14.9 x 9 with a high-side local oscillator, and 10.7 IF gives 123.4MHz. Another crystal at 74MHz oscillates happily at its fundamental in this application.

I would like a "second VFO", be it VXO or whatever. I built a VFO using BF199, just for fun. It drifts down 12kHz from cold, and then wanders hundreds of hertz over a minute. So ok for OIRT spotting, but no good for narrowband.