The push pull has the advantage to deeply attenuate the even harmonics, all versions of the ubitx were good in that, the issue was on odd harmonics, 3rd, 5th.... With push pull a less steeper low pass filter can be used. Especially the 'corner'? frequency can be chosen higher than it would be otherwise. A single low pass filter can also be used for a couple bands. So you save a lot in filtering and relays, it's more a matter of cost and convenience I believe. Monoband qrps are much easier, the ones I had assembled don't have a push pull final, just a normal amplifier and a low pass filter to remove any harmonics. Maybe even I could design a monoband transceiver...

Il 02/dic/2018 20:18, "Simon" <simonhk7@...> ha scritto:

Is push pull generally has higher spectral purity than single end transister ? ? Ubitx is push pull, bitx40 is single end.

I read comments stating that bitx40 has better spectural than ubitx, because it is single band, simpler circuit. Is it true for present batch, revision?? I meant, the comments could refer to many revisions over time. ?

How "bad" is the situation? It is not too far from fcc spec., right? There were quite a number of posting on spectural purity? Is the latest batch solved the issue now.?

73 Simon