76Ghz Equipment
The system shown above comprises a head unit and a PLL local oscillator housed in a diecast box. The head unit is mounted on the rear of a 35cm ex-link dish fed with a penny feed arrangement. An FT290 acts as the 145Mhz IF.
Transverter
This photo shows the head unit of the 76Ghz DB6NT transverter with, from left to right, the 9.5 to 19Ghz doubler, the 19 to 38Ghz doubler and finally the mixer / doubler pcb.
A newer unit shown below dispenses with the 9.5 to 19Ghz doubler and uses a Millicom multiplier to go straight from 9.5Ghz to 38Ghz.
PLL LO
The WA6CGR PLL is shown above, which controls the 9.5Ghz oscillator and provides the LO. This is locked to a surplus ovened 10MHz reference oscillator which can be seen as the shiny cube in the bottom left of the picture. On the underside of this box is another containing the DDK 004 oscillator and a WDG 003 multiplier pcb.
Like the 24Ghz system described elsewhere high stability and good phase noise are a must. Thus the crystal used in the LO must be of high quality and age predictably. The crystals are usually specified for operation with an oven temperature of 60degC and are supplied by Eisch-Kafka.
A "high power" multiplier source
The 76Ghz diode multiplier using an HP dual beam lead diode in a DB6NT transverter pcb, pumped with a 38.1Ghz Millicom x4 multiplier. This is in turn driven by a 9GHz multipier strip which can be keyed or FM modulated. Power output has been measured indirectly as being 18dB up, on the bare diode mixing type transverter, thus it may have ~1mW output!
An alternative transceiver system
Experimentation has been done recently using two dielectric 36dBi horn antennas (above) instead of a single dish. This gets around the need for a waveguide switch for transmit and receive and its thought the horns built for 60Ghz may have better gain than say a homebrew feed system in an ill-illuminated dish of unknown characteristics. This configuration has the high power FM source on one horn and the transverter on the other. Thus one can receive and transmit thro' the tranverter on the right horn or transmit only at slightly higher power on the other while still ensuring alignment on the distant station.