Impressive that the harmonics are NOT a problem.? ?I don't remember ever being much worried by them on my DE, either.
I've seen those low low frequency spurious signals a lot.? ? I think changing the si5351 drive to 2mA thoughout and adding in a tiny bit more bypassing capacitors got rid of most of them.? ?Also increasing the idling current.? ?See article beginning page 9:? ?? ? Increasing the magnification of the page allows the screen shots to be read more easily.? ?I think there may be products in those photos that actually come from mixing in the Heathkit cantenna diode.... but I still got them way way lower...and you can see basically zero 2nd harmonic of the 14MHz signal in the last photo.? ?That was the DE, using RELAYS.? ? If I re-measure it, it may be even cleaner than I knew.? ?
I need to go back and re-measure my DE now that I've removed the unnecessary diode from the Heathkit Cantenna; or else use a "flat" high power pad.? ? My "allowance" (I'm retired, hooray!) will allow me this week to order a higher power version.? ?That makes it a lot easier to do these measurements, because no corrections needed.? ?The one I have already is only good to about 15 watts and I was pushing it pretty hard.? ??
I think this is a ground breaking radio and I'm hoping we can cure any difficulties so that it achieves what it desrves.? ??
You might try increasing your idling current if nothing else fixes those low frequency spurs.
Thanks for publishing those, it helps.
Gordon KX4Z
