I recently finished another short wave regen, this time using alot of screening (lots of recycled bean cans and coax) which works quiet well. Its alot more stable because of the extensive screening used everywhere.
So...now that i have built some simple RF things, and got them working, i'v been thinking of havign a go at a simple superhet.
After reading some stuff about them i think i finally realise how they work. Hopefully, if i understood it, a superhet looks somethign like this.
http://img.photobucket.com/albums/v4.../superhet1.gif
The triode oscillator is pretty straight forward to me, exept the output is taken from the grid. I guess if it was taken from the anode the voltage would be way too high for the mixer.
The mixer can be several things, from a tetrode upwords (and maybe even a triode?) but a hexode heptode or octode are usually used. I also know that sometimes one valve is used for the mixer and osc, utilising a grid pretending to be the oscillator anode.
As far as i know, the trimmers C1 and C2 are there so that they local oscillator is allways exactly at the main frequancy minus the IF frequancy. If the world was perfect, and the ariel tuning coil and the osc coil and theyr capacitors were exactly spot on than technically the trimmers wouldnt be needed. But because the world ISNT perfect, and the coils caps and tuning caps have slight differences, the trimmers are needed to make sure that the gap between both the areil coil and oscilaltor coils resosnat frequancy is thesame.
C3 is a ''padder'' cap. I dont quiet understand how it works, expt that its got somethgin to do with the charectaristics of lc circuits, and it ''corrects'' them so they have the right charectaristics...or soemthgin like that.
Anythign wrong so far?
I'm thinking of building a simple superhet. I'm enclined towards a seperate triode oscillator for now, to keep things less fiddly and easier to debug...and a pentode or hexode mixer.
thanks...