Well, here's another one, same source.
- Variometer tuned xtal rx
Take a close look at it. First thing is the variometer tuning. Changing the inductance of a LC tuned circuit changes the resonant frequency, as seen in permeability tuners often with sliding cores to effect tuning.
There's no circuit shown with the ad, but i suspect that the capacitor for the LC tuning must be under the board, because there is a switch on the right and the set 'boasts' two ranges, AM broadcast as well as a shortwave. Maybe windings of the variometer are switched?
All very unusual. I have never tried a shortwave xtal receiver because i thought the SW antenna signal strength would be too low and a single LC tuner would have nothing like sufficient selectivity. Anyone going to risk buying one? It's tempting....
There's a classic "cat's whisker" detector, which is fun if you have time to fiddle with it, but I guess one could always bridge it with a Ge diode if you lose patience.
Any thoughts about this odd animal?
