There are dozens of sites with useful calculators but I felt that it took a long time to search for them when you needed them, often only to find a broken link so
I have tried to collect the more commonly used formula calculators and tables here as a central reference point, there are links to the less common ones.
Credit/link is given where known to original site.Thanks to all those who have contributed.

 COMMON MICROWAVE DEVICE DATA SHEETS pdf format

 CLY5      CLY10   BFQ34  BFQ68  M57716   M57762   M67715  M68719   RA18H1213G

The RA18H1213 device is designed to superceed the M67762. It is not a direct replacement.,Study the data sheet for differences.
As long as drive level is correctly set these do appear to be more linear at the 30W mark (about 12 Amps DC)
But they quickly become non-linear above this, so for ATV more care may be needed with drive levels.
However reports on the performance for digital transmissions shows marked improvements over the M677762.
One difference is that the backplate has a <1mm recess (see data sheet) .
The raised flanges may need sanding/filing down and then a smear of heat sink compound added to ensure a good thermal contact with the heatsink.

REPAIR NOTES from Mike, G8LES
The module should be set to 4-5amps standing current.
The drive should be kept below 400mW.
Carefully prise the plastic cover off, after running a stanley knife along the glued edge.
The soldering can fail on the coupling chip capacitors between the first and second stage if the drive level is too high.
Pressing down hard on them with a plastic trim tool will prove it.
Most modules can give up to 40 watts continuous into a piece of RG412 directly off the output pin.( They do not like connecting to PCB track.)

Lots of earthing around the module..... maximum every 2 cm PCB link- throughs or screws
The module ceramic PCB normally cracks next to the output transistor and the 12 volt track goes open circuit.
Do not use a "magnastat" Wella soldering iron it will blow up the gates of the FET's
Even an electronically controlled soldering iron must be earthed to the base plate.
Check gate voltage is around 2 volts: if not, the device is damaged.

P.S. from DK: The above notes can also apply to other Mitsu chips, well worth checking the dc feeds for continuity before binning any chip.
Often the cause of cutting out when chip is hot.The spec sheet says when soldering the RA18 onto a board not to exceed 350'C for longer than 3 seconds.

CONVERTING FROM SVHS OUTPUT TO COMPOSITE VIDEO:
SVHS Video Connections (4-pin miniDIN):

Pin 1: Luminance Ground Pin 2: Chrominance Ground Pin 3: Luminance (Y) Pin 4: Chrominance (C)