> Are you sure these work upto 290 mhz?
According to the datasheet specification the top frequency is 200MHz.
However if you ignore this and just configure it for higher and higher frequencies, in my test it really did seem to work fine up until 290MHz. After that the output just gives up. Other QRP Labs kit owners also verified similar maximum frequency around 300MHz.
Of course I have no idea what performance specification may be violated, or no longer guaranteed under all specified conditions, at 290MHz. The wisdom of using the chip up so far outside its specification is debatable, particularly in anything other than a one-off homebrew project.
73 Hans G0UPL