I have found a useful and cheap/simple way to generate a weak signal for the microwave bands is to drive a suitable diode in a WG mount with the output from a TCXO. Suitable diodes are the old cartridge radar mixer types. It also helps to buffer the output of the TCXO with a TTL or CMOS gate or two. The addition of a small horn helps for antenna testing. Suitable TCXOs are available surplus. I use a 12.8 MHz one recovered from an old analogue cellphone. I find that they are useful over a 50 to 100 m range.on 10 GHz. The whole setup can be easily powered form a battery so is very portable..
