Hi Peter,
Thanks for reply!
The Bitx is like most things a compromise design (to keep it simple)
Sure. That's clear and even more - that's the whole beauty in this compromise design that it is so simple and it works! :-)
But... even in such simple design, if there is a bug, it should be fixed, right - just to make it working a bit better and still keep it simple.
yes the single transistor amps and crystal filter have a Zin/Zout of
about 200 ohms while the mixers are 50 ohm so there is mismatch and some
performance lost.
Are you sure?
My analysis (described in the previous post) shows that crystal filter has 50 ohms Zin/Zout, each transistor amp has impedance translation (so its Zout depends on Zin applied) and mixer has 220 ohms on each port.
Yes the Bitx could be better but then it would become more complex, so
the trade-off.
I'm not suggesting to make it more complex. Let's keep it simple, but try to fix any bugs if they are found anywhere in this design :-)
By the way - I'm still not sure if my previous impedance analysis is correct - can anyone confirm?
The bug found (in my opinion) is just wrong Zin/Zout attenuator between 3rd amp and product detector...
Regards,
Rafal SP3GO
