[Test-Equipment] Frequency doubler for 8640A Sig Gen

[Arthur Shulman]

I am experimenting with the construction of a doubler to extend the
range of my 8640A signal generator. The highest range of this model
covers 256-512 mhz, and I wish to have 512-1024 available (for which HP
provided a calibrated scale.

Currently, I am using a MiniCircuits RMS-5 DBM to double. With +10db
drive, I have a conversion gain of 10 db for the second harmonic,
compared to the fundamental. Seems impressive since the DBM is the only
part in the circuit, save for the 2 BNC connectors and a bit of RG174.

Does anyone have any suggestions or tips to make this 'by the book' ?
Filters, pads, etc.?

Arthur Shulman