A linear 5 to 10 MHz doubler that may be of interest is described in the March-April 2011 issue of QEX. I use it to double the output of an Vectron double oven 5 MHz standard to 10 MHz. Extensive design and performance data is provided for the basic breadboard, a PC version of the breadboard and a complete subsystem including an +13 dBm output line driver amplifier with a 50 OHM source impedance. I did not measure the phase noise or ADEY as my applications did not require such. For grins, the basic doubler can be implemented with a connectorized hanging bread board consisting of a double balanced mixer, a power splitter, and a 90 degrees phase shift network. Data on such an arrangement is in the article. The article may be found on the ARRL web site -73 john roos k6iql