Dear Steve and David, many thanks indeed for your replies. Unfortunately, I don’t think we’ll get to solve the problem of finding the range of frequency tuning or output power from the model number that we have (see below), without measuring the device on a spectrum analyser. We are currently in lockdown here in the UK for the next few months; we wanted to use the oscillator to perform some quasi-optical experiments at home. We will try and find the rough range of frequency tuning by trying to spatially measure standing waves, which is about as good as we can do for now albeit with wavelengths of the order of a millimetre.

Our Millitech GDM-12-WB-17M Mechanically-tuned Gunn Oscillator for the RW-12 waveguide band could be at least 20 years old (original purchase order could not be found) and has two micrometer-driven tuning mechanisms: one for the Shorting Piston (frequency tuning) and the other acts as a Tuning Screw (impedance matching for optimal output power). It is driven by a 10V Millitech modulator.

We have conflicting information from the following two online catalogues.

1. Original 2005 and 2006 Millitech Catalogues only indicates the following:
* GDM-12 operating from a 10 V/250 mA supply indicates a frequency of operation from 75-90 GHz (unlike the one driven by a 5 V/1000 mA supply, which operates from 60-75 GHz).
* The ‘GDM Standard Version’ has +/-1% maximum frequency tuning and a minimum available power of 19 dBm (80 mW).
* The ‘GDM Maximum Tuning Version’ has 6 GHz tuning bandwidth and a minimum available power of 16 dBm (40 mW).
* The WB in GDM-12-WB, may refer to ‘Waveguide Band’ or ‘Wide Band’. The latter would indicate the Maximum Tuning Version.

2. Newer Smith Microwave Data Sheet (IS000032 REV 07 ECO #1303-20-01) for the Millitech Series GDM gives the following:
* GDM-12 operates from a 5 V/1000 mA supply at a frequency of operation from either 60-75 GHz or 75-90 GHz.
* The ‘GDM Standard Version’ has +/-1% maximum frequency tuning and a minimum available power of 17 dBm (50 mW).
* The ‘GDM Maximum Tuning Version’ has 4 GHz tuning bandwidth and a minimum available power of 16 dBm (40 mW).
* Specify Model Number: GDM-12-AABBCD (AA = Total Tuning Range; BB = Minimum Output Power (in dBm), C = Special Options, D = Regulator Options)